LT1158IN#TR [Linear]
Half Bridge Based MOSFET Driver, PDIP16;
| 型号： | LT1158IN#TR |
| 厂家： | 
Linear |
| 描述： | Half Bridge Based MOSFET Driver, PDIP16 驱动 光电二极管 接口集成电路 驱动器 |
| 文件： | 总22页 (文件大小：244K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1158
Half Bridge N-Channel
Power MOSFET Driver
FEATURES
DESCRIPTION
+
A single input pin on the LT®1158 synchronously controls
two N-channel power MOSFETs in a totem pole configura-
tion. Unique adaptive protection against shoot-through
currents eliminates all matching requirements for the two
MOSFETs. This greatly eases the design of high efficiency
motor control and switching regulator systems.
n
Drives Gate of Top Side MOSFET Above V
n
Operates at Supply Voltages from 5V to 30V
150ns Transition Times Driving 3000pF
Over 500mA Peak Driver Current
Adaptive Non-Overlap Gate Drives
Continuous Current Limit Protection
Auto Shutdown and Retry Capability
Internal Charge Pump for DC Operation
Built-In Gate Voltage Protection
n
n
n
n
n
n
n
n
n
n
A continuous current limit loop in the LT1158 regulates
short-circuit current in the top power MOSFET. Higher
start-up currents are allowed as long as the MOSFET V
does not exceed 1.2V. By returning the FAULT output to
the enable input, the LT1158 will automatically shut down
in the event of a fault and retry when an internal pull-up
current has recharged the enable capacitor.
DS
Compatible with Current-Sensing MOSFETs
TTL/CMOS Input Levels
Fault Output Indication
APPLICATIONS
An on-chip charge pump is switched in when needed to
turn on the top N-channel MOSFET continuously. Special
circuitry ensures that the top side gate drive is safely
maintained in the transition between PWM and DC opera-
tion. The gate-to-source voltages are internally limited to
14.5V when operating at higher supply voltages.
n
PWM of High Current Inductive Loads
n
Half Bridge and Full Bridge Motor Control
n
Synchronous Step-Down Switching Regulators
n
Three-Phase Brushless Motor Drive
n
High Current Transducer Drivers
n
Battery-Operated Logic-Level MOSFETs
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
5365118.
TYPICAL APPLICATION
24V
1N4148
Top and Bottom Gate Waveforms
0.1μF
BOOST DR
+
BOOST
V
T GATE DR
+
IRFZ34
+
+
500μF
LOW
ESR
+
10μF
V
T GATE FB
T SOURCE
PWM
0Hz TO
100kHz
+
+
INPUT
SENSE
LT1158
R
SENSE
0.015Ω
–
LOAD
ENABLE
FAULT
BIAS
SENSE
–
1158 TA02
V
= 24V
= 12Ω
IN
L
1μF
R
B GATE DR
B GATE FB
IRFZ34
0.01μF
GND
LT1158 TA01
1158fb
1
LT1158
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage (Pins 2, 10) ......................................36V
Boost Voltage (Pin 16)..............................................56V
Continuous Output Currents (Pins 1, 9, 15).........100mA
Operating Temperature Range
LT1158C................................................... 0°C to 70°C
LT1158I................................................–40°C to 85°C
Junction Temperature (Note 2)
+
Sense Voltages (Pins 11, 12).................. –5V to V + 5V
+
Top Source Voltage (Pin 13) ................... –5V to V + 5V
LT1158C............................................................ 125°C
LT1158I............................................................. 150°C
Storage Temperature Range...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec.) ................. 300°C
Boost to Source Voltage (V16 – V13) ........ –0.3V to 20V
PIN CONFIGURATION
TOP VIEW
TOP VIEW
BOOST DR
1
2
3
4
5
6
7
8
16 BOOST
BOOST DR
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
BOOST
+
+
V
15 T GATE DR
V
T GATE DR
T GATE FB
T SOURCE
BIAS
ENABLE
FAULT
14
13
12
11
10
9
T GATE FB
T SOURCE
BIAS
ENABLE
FAULT
+
+
SENSE
SENSE
–
–
INPUT
SENSE
INPUT
SENSE
+
+
GND
V
GND
V
B GATE FB
B GATE DR
B GATE FB
B GATE DR
SW PACKAGE
16-LEAD PLASTIC (WIDE) SO
= 110°C/W
N PACKAGE
16-LEAD PLASTIC DIP
= 70°C/W
θ
θ
JA
JA
ORDER INFORMATION
LEAD FREE FINISH
LT1158CN#PBF
LT1158IN#PBF
LT1158CSW#PBF
LT1158ISW#PBF
LEAD BASED FINISH
LT1158CN
TAPE AND REEL
LT1158CN#TRPBF
LT1158IN#TRPBF
LT1158CSW#TRPBF
LT1158ISW#TRPBF
TAPE AND REEL
LT1158CN#TR
PART MARKING*
PACKAGE DESCRIPTION
16-Lead Plastic DIP
16-Lead Plastic DIP
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
16-Lead Plastic (Wide) SO
16-Lead Plastic (Wide) SO
PACKAGE DESCRIPTION
16-Lead Plastic DIP
–40°C to 85°C
TEMPERATURE RANGE
0°C to 70°C
PART MARKING*
LT1158IN
LT1158IN#TR
16-Lead Plastic DIP
–40°C to 85°C
0°C to 70°C
LT1158CSW
LT1158CSW#TR
LT1158ISW#TR
16-Lead Plastic (Wide) SO
16-Lead Plastic (Wide) SO
LT1158ISW
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
1158fb
2
LT1158
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. Test Circuit, V+ = V16 = 12V, V11 = V12 = V13 = 0V, Pins 1 and 4 open,
Gate Feedback pins connected to Gate Drive pins unless otherwise specified.
LT1158I
TYP
LT1158C
TYP MAX UNITS
SYMBOL
I + I
PARAMETER
CONDITIONS
+
MIN
MAX
MIN
DC Supply Current (Note 2) V = 30V, V16 = 15V, V4 = 0.5V
2.2
7
13
3
10
18
2.2
7
3
10
18
mA
mA
mA
2
10
+
+
V = 30V, V16 = 15V, V6 = 0.8V
4.5
8
4.5
8
V = 30V, V16 = 15V, V6 = 2V
13
+
I
Boost Current
V = V13 = 30V, V16 = 45V, V6 = 0.8V
3
1.4
5
4.5
2
3
1.4
5
4.5
2
mA
V
16
l
l
l
l
l
V6
Input Threshold
0.8
0.8
I
Input Current
V6 = 5V
15
1.4
1.7
35
15
1.4
1.8
35
μA
V
6
V4
Enable Low Threshold
Enable Hysteresis
Enable Pullup Current
Charge Pump Voltage
V6 = 0.8V, Monitor V9
V6 = 0.8V, Monitor V9
V4 = 0V
0.9
1.3
15
1.15
1.5
25
0.85
1.2
15
1.15
1.5
25
ΔV4
V
I
μA
4
+
+
l
l
V15
9
40
11
43
9
40
11
43
V
V
V = 5V, V6 = 2V, Pin 16 open, V13 → 5V
47
17
17
2.5
2
47
17
17
2.5
2
V = 30V, V6 = 2V, Pin16 open, V13 → 30V
+
l
l
V9
V1
Bottom Gate “ON” Voltage
Boost Drive Voltage
V = V16 = 18V, V6 = 0.8V
12
12
1
14.5
14.5
1.75
1.5
12
12
1
14.5
14.5
1.75
1.5
V
V
+
V = V16 = 18V, V6 = 0.8V, 100mA Pulsed Load
+
V14 – V13 Top Turn-Off Threshold
V = V16 = 5V, V6 = 0.8V
V
+
V8
Bottom Turn-Off Threshold
Fault Output Leakage
V = V16 = 5V, V6 = 2V
1
1
V
+
l
I
V = 30V, V16 = 15V, V6 = 2V
0.1
1
0.1
1
μA
V
5
+
V5
Fault Output Saturation
V = 30V, V16 = 15V, V6 = 2V, I = 10mA
0.5
1
0.5
1
5
+
V12 – V11 Fault Conduction Threshold V = 30V, V16 = 15V, V6 = 2V, I = 100μA
90
110
150
130
85
110
150
135
mV
5
+
V12 – V11 Current Limit Threshold
V = 30V, V16 = 15V, V6 = 2V, Closed Loop
130
120
170
180
120
120
180
180
mV
mV
l
+
V12 – V11 Current Limit Inhibit
V = V12 = 12V, V6 = 2V, Decrease V11
1.1
1.25
1.4
1.1
1.25
1.4
V
V
Threshold
Until V15 Goes Low
DS
l
l
l
l
l
l
t
t
t
t
t
t
Top Gate Rise Time
Top Gate Turn-Off Delay
Top Gate Fall Time
Pin 6 (+) Transition, Meas. V15 – V13 (Note 4)
Pin 6 (–) Transition, Meas. V15 – V13 (Note 4)
Pin 6 (–) Transition, Meas. V15 – V13 (Note 4)
Pin 6 (–) Transition, Meas. V9 (Note 4)
130
350
120
130
200
100
250
550
250
250
400
200
130
350
120
130
200
100
250
550
250
250
400
200
ns
ns
ns
ns
ns
ns
R
D
F
Bottom Gate Rise Time
R
D
F
Bottom Gate Turn-Off Delay Pin 6 (+) Transition, Meas. V9 (Note 4)
Bottom Gate Fall Time Pin 6 (+) Transition, Meas. V9 (Note 4)
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 3: Dynamic supply current is higher due to the gate charge
being delivered at the switching frequency. See typical performance
characteristics and applications information.
Note 4: Gate rise times are measured from 2V to 10V, delay times are
Note 2: T is calculated from the ambient temperature T and power
measured from the input transition to when the gate voltage has decreased
to 10V, and fall times are measured from 10V to 2V.
J
A
dissipation P according to the following formulas:
D
LT1158IN, LT1158CN: T = T + (P × 70°C/W)
J
A
D
LT1158ISW, LT1158CSW: T = T + (P × 110°C/W)
J
A
D
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3
LT1158
TYPICAL PERFORMANCE CHARACTERISTICS
DC Supply Current
DC Supply Current
Dynamic Supply Current (V+)
14
12
14
12
30
25
20
15
10
5
I
+ I + I
10 16
2
50% DUTY CYCLE
V13 = 0V
INPUT HIGH
I
+ I + I
10 16
2
+
V
= 12V
C
= 3000pF
GATE
+
V13 = V
INPUT HIGH
INPUT LOW
10
8
10
+
INPUT LOW
V
= 24V
8
6
4
2
+
V
= 12V
6
+
V
= 6V
4
ENABLE LOW
ENABLE LOW
2
0
0
0
10
20
SUPPLY VOLTAGE (V)
35 40
50
TEMPERATURE (°C)
100 125
0
5
15
25 30
–50 –25
0
25
75
1
10
INPUT FREQUENCY (kHz)
100
LT1158 G01
LT1158 G02
LT1158 G03
Dynamic Supply Current
Charge Pump Output Voltage
Input Thresholds
40
35
30
25
20
15
10
5
50
45
40
35
30
25
20
15
10
5
2.0
1.8
1.6
1.4
1.2
1.0
0.8
50% DUTY CYCLE
+
V
= 12V
V(HIGH)
–40°C
+25°C
+85°C
NO LOAD
C
= 10000pF
GATE
–40°C
+25°C
+85°C
C
= 3000pF
GATE
10μA LOAD
V(LOW)
C
= 1000pF
GATE
0
0
1
10
INPUT FREQUENCY (kHz)
100
30
SUPPLY VOLTAGE (V)
0
5
10
20 25
35 40
0
20
30 35
15
5
10 15
25
40
SUPPLY VOLTAGE (V)
LT1158 G04
LT1158 G06
LT1158 G05
Enable Thresholds
Fault Conduction Threshold
Current Limit Threshold
3.5
3.0
160
150
140
130
120
110
100
90
200
190
180
170
160
150
140
130
120
110
100
CLOSED LOOP
V11 = 0V
V(HIGH)
–40°C
+85°C
+25°C
2.5
2.0
1.5
1.0
0.5
+85°C
+25°C
+85°C
+25°C
–40°C
–40°C
+85°C
–40°C
+25°C
V(LOW)
80
70
0
60
10
20
35 40
0
5
15
25 30
0
20
30 35
0
20
30 35
5
10 15
25
40
5
10 15
25
40
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
LT1158 G07
LT1158 G08
LT1158 G09
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4
LT1158
TYPICAL PERFORMANCE CHARACTERISTICS
Current Limit Inhibit
VDS Threshold
Bottom Gate Rise Time
Bottom Gate Fall Time
1.50
1.45
1.40
1.35
1.30
1.25
1.20
1.15
1.10
1.05
1.00
400
350
300
250
200
150
100
50
400
350
300
250
200
150
100
50
V2 – V11
C
= 10000pF
GATE
C
= 10000pF
GATE
–40°C
+25°C
+85°C
C
= 3000pF
= 1000pF
C
= 3000pF
= 1000pF
GATE
GATE
C
GATE
C
GATE
0
0
5
15 20 25
SUPPLY VOLTAGE (V)
35
5
15 20 25
SUPPLY VOLTAGE (V)
35
0
10
30
40
0
10
30
40
0
20
30 35
5
10 15
25
40
SUPPLY VOLTAGE (V)
LT1158 G11
LT1158 G12
LT1158 G10
Top Gate Rise Time
Top Gate Fall Time
Transition Times vs RGate
800
700
400
350
300
250
200
150
100
50
400
350
300
250
200
150
100
50
+
V
C
= 12V
= 3000pF
GATE
C
= 10000pF
GATE
600
500
400
300
C
= 10000pF
GATE
RISE TIME
C
= 3000pF
= 1000pF
GATE
GATE
FALL TIME
C
= 3000pF
= 1000pF
GATE
200
100
0
C
GATE
C
0
0
5
15 20 25
10
SUPPLY VOLTAGE (V)
35
5
15 20 25
10
SUPPLY VOLTAGE (V)
35
70
80 90 100
0
30
40
0
30
40
0
10 20 30 40 50 60
GATE RESISTANCE (Ω)
LT1158 G13
LT1158 G14
LT1158 G15
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5
LT1158
PIN FUNCTIONS
BOOST DR (Pin 1): Recharges and clamps the bootstrap
capacitor to 14.5V higher than pin 13 via an external
diode.
+
V (Pin10):Bottomsidedriversupply;mustbeconnected
to the same supply as pin 2.
–
SENSE (Pin 11): The floating reference for the current
+
V (Pin 2): Main supply pin; must be closely decoupled
limit comparator. Connects to the low side of a current
shunt or Kelvin lead of a current-sensing MOSFET. When
to the ground pin 7.
+
pin 11 is within 1.2V of V , current limit is inhibited.
BIAS (Pin 3): Decouple point for the internal 2.6V bias
generator. Pin 3 cannot have any external DC loading.
+
SENSE (Pin 12): Connects to the high side of the current
shuntorsenseleadofacurrent-sensingMOSFET.Abuilt-in
offsetbetweenpins11and12inconjunctionwithRSENSE
sets the top MOSFET short-circuit current.
ENABLE (Pin 4): When left open, the LT1158 operates
normally. Pulling pin 4 low holds both MOSFETs off re-
gardless of the input state.
T SOURCE (Pin 13): Top side driver return; connects to
MOSFET source and low side of the bootstrap capacitor.
FAULT (Pin 5): Open collector NPN output which turns
on when V12 – V11 exceeds the fault conduction thresh-
old.
TGATEFB(Pin14):Mustconnectdirectlytothetoppower
MOSFET gate. The bottom MOSFET turn-on is inhibited
untilV14–V13hasdischargedto1.75V.Anon-chipcharge
pump also feeds the top gate via pin 14.
INPUT (Pin 6): Taking pin 6 high turns the top MOSFET on
and bottom MOSFET off; pin 6 low reverses these states.
Aninputlatchcaptureseachlowstate,ignoringanensuing
high until pin 13 has gone below 2.6V.
T GATE DR (Pin 15): The high current drive point for the
top MOSFET. When a gate resistor is used, it is inserted
between pin 15 and the gate of the MOSFET.
B GATE FB (Pin 8): Must connect directly to the bottom
power MOSFET gate. The top MOSFET turn-on is inhibited
untilpin8hasdischargedto1.5V.Ahold-oncurrentsource
also feeds the bottom gate via pin 8.
BOOST (Pin 16): Top side driver supply; connects to the
high side of the bootstrap capacitor and to a diode either
+
+
from supply (V < 10V) or from pin 1 (V > 10V).
B GATE DR (Pin 9): The high current drive point for the
bottomMOSFET.Whenagateresistorisused,itisinserted
between pin 9 and the gate of the MOSFET.
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6
LT1158
BLOCK DIAGRAM
+
BOOST
16
V
+
V
CHG
PUMP
BOOST DR
1
2
15
14
T GATE DR
T GATE FB
+
+
V
V
15V
BIAS
GEN
LOGIC
INPUT
3
BIAS
–
+
T
25μA
1.75V
+
–
ENABLE
4
5
13
T SOURCE
7.5V
2.7V
1.2V
110mV
FAULT
+
+
–
12
11
SENSE
S
–
SENSE
–
+
O
2.6V
7.5V
+
10
V
1-SHOT
R
S
R
+
–
INPUT
6
Q
Q
1.4V
15V
B GATE DR
9
1-SHOT
R
–
+
B
1.5V
GND
7
8
1158 FD
B GATE FB
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7
LT1158
TEST CIRCUIT
150Ω
2W
16
15
14
13
12
11
10
9
1
2
BOOST DR
BOOST
T GATE DR
T GATE FB
T SOURCE
+
+
VN2222LL
1μF
V16
+
V
+
0.01μF
+
+
3
4
5
6
7
8
V
10μF
BIAS
2k
1/2W
3000pF
+
ENABLE
FAULT
INPUT
GND
V14 – V13
+
LT1158
+
CLOSED
LOOP
V4
SENSE
3k
1/2W
100Ω
+
–
SENSE
V12
V6
+
50Ω
+
V
V11
B GATE FB
B GATE DR
3000pF
+
V8
LT1158 TC01
(Refer to Functional Diagram)
OPERATION
The LT1158 self-enables via an internal 25μA pull-up on
the enable pin 4. When pin 4 is pulled down, much of the
input logic is disabled, reducing supply current to 2mA.
Withpin4low, theinputstateisignoredandbothMOSFET
gates are actively held low. With pin 4 enabled, one or the
other of the 2 MOSFETs is turned on, depending on the
state of the input pin 6: high for top side on, and low for
bottom side on. The 1.4V input threshold is regulated and
has 200mV of hysteresis.
Whenever there is an input transition on pin 6, the LT1158
followsalogicalsequencetoturnoffoneMOSFETandturn
on the other. First, turn-off is initiated, then V is moni-
GS
tored until it has decreased below the turn-off threshold,
and finally the other gate is turned on. An input latch gets
reset by every low state at pin 6, but can only be set if the
top source pin has gone low, indicating that there will be
sufficient charge in the bootstrap capacitor to safely turn
on the top MOSFET.
In order to allow operation over 5V to 30V nominal supply
voltages, an internal bias generator is employed to furnish
constant bias voltages and currents. The bias generator is
decoupled at pin 3 to eliminate any effects from switching
transients. No DC loading is allowed on pin 3.
In order to conserve power, the gate drivers only provide
turn-on current for up to 2μs, set by internal one-shot
circuits. Each LT1158 driver can deliver 500mA for 2μs,
or 1000nC of gate charge––more than enough to turn on
multiple MOSFETs in parallel. Once turned on, each gate
is held high by a DC gate sustaining current: the bottom
gate by a 100μA current source, and the top gate by an
on-chip charge pump running at approximately 500kHz.
The top and bottom gate drivers in the LT1158 each utilize
two gate connections: 1) A gate drive pin, which provides
theturn-onandturn-offcurrentsthroughanoptionalseries
gate resistor; and 2) A gate feedback pin which connects
directly to the gate to monitor the gate-to-source voltage
and supply the DC gate sustaining current.
The floating supply for the top side driver is provided by
a bootstrap capacitor between the boost pin 16 and top
sourcepin13.Thiscapacitorisrechargedeachtimepin13
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8
LT1158
(Refer to Functional Diagram)
OPERATION
goeslowinPWMoperation,andismaintainedbythecharge
pump when the top MOSFET is on DC. A regulated boost
driver at pin 1 employs a source-referenced 15V clamp
that prevents the bootstrap capacitor from overcharging
comparator input pins 11 and 12 are normally connected
across a shunt in the source of the top power MOSFET
(or to a current-sensing MOSFET). When pin 11 is more
+
than 1.2V below V and V12 – V11 exceeds the 110mV
+
regardless of V or output transients.
offset, FAULT pin 5 begins to sink current. During a short
circuit, the feedback loop regulates V12 – V11 to 150mV,
thereby limiting the top MOSFET current.
TheLT1158providesacurrent-sensecomparatorandfault
output circuit for protection of the top power MOSFET. The
APPLICATIONS INFORMATION
Power MOSFET Selection
and the available heat sinking has a thermal resistance of
20°C/W, the MOSFET junction temperature will be 125°C,
and∂=0.007(125–25)=0.7.Thismeansthattherequired
Since the LT1158 inherently protects the top and bottom
MOSFETsfromsimultaneousconduction,therearenosize
or matching constraints. Therefore selection can be made
R
of the MOSFET will be 0.089Ω/1.7 = 0.0523Ω,
DS(ON)
which can be satisfied by an IRFZ34.
basedontheoperatingvoltageandR
requirements.
DS(ON)
should be at least 2 • V
The MOSFET BV
, and
Notethatthesecalculationsareforthecontinuousoperating
condition; power MOSFETs can sustain far higher dissipa-
DSS
SUPPLY
should be increased to 3 • V
with frequent fault conditions. For the LT1158 maximum
in harsh environments
SUPPLY
tionsduringtransients.AdditionalR
)constraintsare
DS(ON)
operating supply of 30V, the MOSFET BV
from 60V to 100V.
should be
discussed under Starting High In-Rush Current Loads.
DSS
TheMOSFETR
isspecifiedatT =25°Candisgener-
J
DS(ON)
ally chosen based on the operating efficiency required as
longasthemaximumMOSFETjunctiontemperatureisnot
exceeded. The dissipation in each MOSFET is given by:
GATE DR
LT1158
GATE FB
R
G
R
G
2
P=D I
1+ ∂ R
DS ON
(
)
(
)
DS
(
)
R : OPTIONAL 10Ω
G
1158 F01
where D is the duty cycle and ∂ is the increase in R
DS(ON)
Figure 1. Paralleling MOSFETs
attheanticipatedMOSFETjunctiontemperature.Fromthis
equation the required R
can be derived:
DS(ON)
Paralleling MOSFETs
MOSFETs can be paralleled. The MOSFETs will inherently
share the currents according to their R ratio. The
P
RDS ON
=
(
)
2
D I
1+ ∂
DS(ON)
(
)
)
(
DS
LT1158 top and bottom drivers can each drive four power
MOSFETs in parallel with only a small loss in switching
speeds (see Typical Performance Characteristics). Indi-
vidual gate resistors may be required to “decouple” each
MOSFET from its neighbors to prevent high frequency
oscillations—consult manufacturer’s recommendations.
For example, if the MOSFET loss is to be limited to 2W
when operating at 5A and a 90% duty cycle, the required
R
would be 0.089Ω/(1 + ∂). (1 + ∂) is given for
DS(ON)
each MOSFET in the form of a normalized R
vs
DS(ON)
temperature curve, but ∂ = 0.007/°C can be used as an
approximationforlowvoltageMOSFETs. ThusifT =85°C
A
1158fb
9
LT1158
APPLICATIONS INFORMATION
If individual gate decoupling resistors are used, the gate
feedback pins can be connected to any one of the gates.
MOSFET Gate Drive Protection
For supply voltages of over 8V, the LT1158 will protect
standardN-channelMOSFETsfromunderorovervoltage
gate drive conditions for any input duty cycle including
DC. Gate-to-source Zener clamps are not required and
not recommended since they can reduce operating
efficiency.
Driving multiple MOSFETs in parallel may restrict the
operating frequency at high supply voltages to prevent
over-dissipation in the LT1158 (see Gate Charge and
DriverDissipationbelow).Whenthetotalgatecapacitance
exceeds 10,000pF on the top side, the bootstrap capacitor
should be increased proportionally above 0.1μF.
A discontinuity in tracking between the output pulse
width and input pulse width may be noted as the top side
MOSFET approaches 100% duty cycle. As the input low
signal becomes narrower, it may become shorter than
the time required to recharge the bootstrap capacitor to
a safe voltage for the top side driver. Below this duty cycle
the output pulse width will stop tracking the input until
the input low signal is <100ns, at which point the output
will jump to the DC condition of top MOSFET “on” and
bottom MOSFET “off.”
Gate Charge and Driver Dissipation
A useful indicator of the load presented to the driver by a
power MOSFET is the total gate charge Q , which includes
G
theadditionalchargerequiredbythegate-to-drainswing.Q
G
is usually specified for V = 10V and V = 0.8V .
GS
DS
DS(MAX)
When the supply current is measured in a switching ap-
plication, it will be larger than given by the DC electrical
characteristics because of the additional supply current
associated with sourcing the MOSFET gate charge:
Low Voltage Operation
dQ
dt
dQ
G
dt
⎛
⎞
⎛
⎞
G
The LT1158 can operate from 5V supplies (4.5V min) and
in 6V battery-powered applications by using logic-level
N-channel power MOSFETs. These MOSFETs have 2V
ISUPPLY =IDC +
+
⎜
⎝
⎟
⎠
⎜
⎝
⎟
⎠
TOP
BOTTOM
The actual increase in supply current is slightly higher
due to LT1158 switching losses and the fact that the gates
are being charged to more than 10V. Supply current vs
switching frequency is given in the Typical Performance
Characteristics.
maximumthresholdvoltagesandguaranteedR
limits
DS(ON)
at V = 4V. The switching speed of the LT1158, unlike
GS
CMOS drivers, does not degrade at low supply voltages.
For operation down to 4.5V, the boost pin should be con-
nected as shown in Figure 2 to maximize gate drive to the
top side MOSFET. Supply voltages over 10V should not
be used with logic-level MOSFETs because of their lower
maximum gate-to-source voltage rating.
The LT1158 junction temperature can be estimated by
using the equations given in Note 1 of the electrical char-
acteristics. For example, the LT1158SI is limited to less
than 25mA from a 24V supply:
5V
N.C.
T
= 85°C + (25mA • 24V • 110°C/W)
= 151°C exceeds absolute maximum
J
+
D1
BOOST DR
BOOST
In order to prevent the maximum junction temperature
from being exceeded, the LT1158 supply current must
be checked with the actual MOSFETs operating at the
maximum switching frequency.
0.1μF
T GATE DR
T GATE FB
T SOURCE
LT1158
LOGIC-LEVEL
MOSFET
D1: LOW-LEAKAGE SCHOTTKY
BAT85 OR EQUIVALENT
LT1158 F02
Figure 2. Low Voltage Operation
1158fb
10
LT1158
APPLICATIONS INFORMATION
Ugly Transient Issues
regulators. Most step-down regulators use a high current
Schottky diode to conduct the inductor current when the
switch is off. The fractions of the oscillator period that the
switch is on (switch conducting) and off (diode conduct-
ing) are given by:
In PWM applications the drain current of the top MOSFET
is a square wave at the input frequency and duty cycle.
To prevent large voltage transients at the top drain, a low
ESR electrolytic capacitor must be used and returned to
the power ground. The capacitor is generally in the range
of 250μF to 5000μF and must be physically sized for
the RMS current flowing in the drain to prevent heating
and premature failure. In addition, the LT1158 requires a
separate 10μF capacitor connected closely between pins
2 and 7.
⎛
⎞
VOUT
SWITCH“ON”=
• TOTALPERIOD
⎜
⎟
V
⎝
⎠
IN
⎛
⎞
V − VOUT
IN
SWITCH“OFF”=
• TOTALPERIOD
⎜
⎟
V
⎝
⎠
IN
Note that for V > 2V , the switch is off longer than it
IN
OUT
The LT1158 top source and sense pins are internally
protected against transients below ground and above
supply. However, the gate drive pins cannot be forced
below ground. In most applications, negative transients
coupled from the source to the gate of the top MOSFET
do not cause any problems. However, in some high cur-
rent (10A and above) motor control applications, negative
transients on the top gate drive may cause early tripping
of the current limit. A small Schottky diode (BAT85) from
pin 15 to ground avoids this problem.
is on, making the diode losses more significant than the
switch. The worst case for the diode is during a short cir-
cuit, when V
approaches zero and the diode conducts
OUT
the short-circuit current almost continuosly.
Figure 3 shows the LT1158 used to synchronously drive a
pair of power MOSFETs in a step-down regulator applica-
tion, where the top MOSFET is the switch and the bottom
MOSFET replaces the Schottky diode. Since both conduc-
tionpathshavelowlosses,thisapproachcanresultinvery
high efficiency—from 90% to 95% in most applications.
Switching Regulator Applications
And for regulators under 5A, using low R
N-channel
DS(ON)
MOSFETs eliminates the need for heatsinks.
The LT1158 is ideal as a synchronous switch driver to
improve the efficiency of step-down (buck) switching
V
IN
+
T GATE DR
T GATE FB
R
GS
R
SENSE
V
T SOURCE
OUT
+
LT1158
+
SENSE
SENSE
–
FAULT
REF
PWM
B GATE DR
B GATE FB
INPUT
1158 F03
Figure 3. Adding Synchronous Switching to a Step-Down Switching Regulator
1158fb
11
LT1158
APPLICATIONS INFORMATION
100
Current Limit in Switching Regulator Applications
Current is sensed by the LT1158 by measuring the voltage
acrossacurrentshunt(lowvaluedresistor).Normally,this
shunt is placed in the source lead of the top MOSFET (see
Short-Circuit Protection in Bridge Applications). However,
in step-down switching regulator applications, the remote
current sensing capability of the LT1158 allows the actual
inductor current to be sensed. This is done by placing
the shunt in the output lead of the inductor as shown in
Figure 3. Routing of the SENSE and SENSE PC traces
is critical to prevent stray pickup. These traces must be
routed together at minimum spacing and use a Kelvin
connection at the shunt.
90
FIGURE 12 CIRCUIT
IN
V
= 12V
80
70
60
+
–
1.5 2.0 2.5
OUTPUT CURRENT (A)
3.5
4.0
0
0.5 1.0
3.0
LT1158 F04
Figure 4. Typical Efficiency Curve for Step-Down
Regulator with Synchronous Switch
When the voltage across R
exceeds 110mV, the
SENSE
One fundamental difference in the operation of a step-
down regulator with synchronous switching is that it
never becomes discontinuous at light loads. The induc-
tor current doesn’t stop ramping down when it reaches
zero, but actually reverses polarity resulting in a constant
ripple current independent of load. This does not cause
any efficiency loss as might be expected, since the nega-
LT1158FAULTpinbeginstoconduct.ByfeedingtheFAULT
signal back to a control input of the PWM, the LT1158 will
assume control of the duty cycle forming a true current
mode loop to limit the output current:
110mV
RSENSE
IOUT
=
in current limit
tive inductor current is returned to V when the switch
IN
In LT3525 based circuits, connecting the FAULT pin to
the LT3525 soft-start pin accomplishes this function. In
circuitswheretheLT1158inputisbeingdrivenwitharamp
or sawtooth, the FAULT pin is used to pull down the DC
level of the input.
turns back on.
The LT1158 performs the synchronous MOSFET drive
and current sense functions in a step-down switching
regulator. A reference and PWM are required to complete
the regulator. Any voltage-mode PWM controller may be
used, but the LT3525 is particularly well suited to high
power, high efficiency applications such as the 10A circuit
shown in Figure 13. In higher current regulators a small
SchottkydiodeacrossthebottomMOSFEThelpstoreduce
reverse-recovery switching losses.
The constant off-time circuits shown in Figures 10 and 12
are unique in that they also use the current sense during
normal operation. The LT1431 output reduces the normal
LT1158 110mV fault conduction threshold such that the
FAULT pin conducts at the required load current, thus
discharging the input ramp capacitor. In current limit the
LT1431 output turns off, allowing the fault conduction
threshold to reach its normal value.
The LT1158 input pin can also be driven directly with a
ramp or sawtooth. In this case, the DC level of the input
waveform relative to the 1.4V threshold sets the LT1158
duty cycle. In the 5V to 3.3V converter circuit shown in
Figure11,anLT1431controlstheDClevelofatrianglewave
generated by a CMOS 555. The Figure 10 and 12 circuits
use an RC network to ramp the LT1158 input back up to
its 1.4V threshold following each switch cycle, setting a
constant off time. Figure 4 shows the efficiency vs output
TheresistorR showninFigure3isnecessarytoprevent
GS
output voltage overshoot due to charge coupled into the
gate of the top MOSFET by a large start-up dv/dt on V .
IN
If DC operation of the top MOSFET is required, R must
GS
be 330k or greater to prevent loading the charge pump.
current for the Figure 12 regulator with V = 12V.
IN
1158fb
12
LT1158
APPLICATIONS INFORMATION
Low Current Shutdown
(Figure 6). For the current-sensing MOSFET shown in
Figure 7, the sense resistor is inserted between the sense
and Kelvin leads.
The LT1158 may be shutdown to a current level of 2mA by
pulling the enable pin 4 low. In this state both the top and
bottomMOSFETsareactivelyheldoffagainstanytransients
which might occur on the output during shutdown. This
is important in applications such as 3-phase DC motor
control when one of the phases is disabled while the other
two are switching.
+
–
TheSENSE andSENSE PCtracesmustberoutedtogether
at minimum spacing to prevent stray pickup, and a Kelvin
connectionmustbeusedatthecurrentshuntforthe3-lead
MOSFET. Using a twisted pair is the safest approach and
is recommended for sense runs of several inches.
If zero standby current is required and the load returns to
ground, then a switch can be inserted into the supply path
When the voltage across R
exceeds 110mV, the
SENSE
LT1158 FAULT pin begins to conduct, signaling a fault
condition.Thecurrentinashortcircuitrampsveryrapidly,
limited only by the series inductance and ultimately the
MOSFET and shunt resistance. Due to the response time
of the LT1158 as shown in Figure 5. Resistor R ensures
GS
that the top MOSFET gate discharges, while the voltage
across the bottom MOSFET goes to zero. The voltage drop
across the P-channel supply switch must be less than
+
V
300mV, andR mustbe330korgreaterforDCoperation.
GS
Thistechniqueisnotrecommendedforapplicationswhich
+
T GATE DR
require the LT1158 V sensing function.
DS
T GATE FB
+
V
T SOURCE
5V
+
LT1158
+
SENSE
SENSE
100k
R
T GATE DR
VP0300
10k
SENSE
–
FAULT
+
T GATE FB
V
2N2222
R
GS
+
V
100k
T SOURCE
1158 F06
LT1158
CMOS
ON/OFF
+
LOAD
TO OTHER
CONTROL
CIRCUITS
Figure 6. Short-Circuit Protection with Standard MOSFET
GND
B GATE DR
B GATE FB
+
V
1158 F05
+
T GATE DR
Figure 5. Adding Zero Current Shutdown
T GATE FB
KELVIN
SENSE
Short-Circuit Protection in Bridge Applications
T SOURCE
R
5V
SENSE
LT1158
+
SENSE
The LT1158 protects the top power MOSFET from output
shorts to ground, or in a full bridge application, shorts
across the load. Both standard 3-lead MOSFETs and cur-
rent-sensing5-leadMOSFETscanbeprotected.Thebottom
MOSFET is not protected from shorts to supply.
OUTPUT
10k
–
SENSE
FAULT
1158 F07
Current is sensed by measuring the voltage across a cur-
rent shunt in the source lead of a standard 3-lead MOSFET
Figure 7. Short-Circuit Protection with Current-Sensing MOSFET
1158fb
13
LT1158
APPLICATIONS INFORMATION
the value of R
for the 5-lead MOSFET increases by
of the LT1158 current limit loop, an initial current spike of
SENSE
the current sensing ratio (typically 1000 – 3000), thus
eliminating the need for a low valued shunt. ΔV is in the
range of 1V to 3V in most applications.
from 2 to 5 times the final value will be present for a few
μs, followed by an interval in which I = 0. The current
DS
spike is normally well within the safe operating area (SOA)
of the MOSFET, but can be further reduced with a small
(0.5μH) inductor in series with the output.
Assuming a dead short, the MOSFET dissipation will rise
to V
• I . For example, with a 24V supply and I
SUPPLY SC
SC
= 10A, the dissipation would be 240W. To determine how
longtheMOSFETcanremainatthisdissipationlevelbefore
it must be shut down, refer to the SOA curves given in
the MOSFET data sheet. For example, an IRFZ34 would
be safe if shut down within 10ms.
A Tektronix A6303 current probe is highly recommended
for viewing output fault currents.
I
SC
If Short-Circuit Protection is Not Required
5μs/DIV
In applications which do not require the current sense
capability of the LT1158, the sense pins 11 and 12 should
both be connected to pin 13, and the FAULT pin 5 left
open. The enable pin 4 may still be used to shut down
the device. Note, however, that when unprotected the top
MOSFET can be easily (and often dramatically) destroyed
by even a momentary short.
LT1158 F08
Figure 8. Top MOSFET Short-Circuit Turn-On current
If neither the enable nor input pins are pulled low in
response to the fault indication, the top MOSFET current
will recover to a steady-state value I regulated by the
LT1158 as shown in Figure 8:
SC
Self-Protection with Automatic Restart
150mV
ISC =
When using the current sense circuits of Figures 6 and 7,
RSENSE
local shutdown can be achieved by connecting the FAULT
150mV
ISC
RSENSE
=
pin through resistor R to the enable pin as shown in
F
Figure 9. An optional thermostat mounted to the load or
−2
MOSFET heatsink can also be used to pull enable low.
r 150mV
RSENSE
(
)
150mV
⎛
⎞
ISC =
1−
⎜
⎝
⎟
⎠
Aninternal25μAcurrentsourcenormallykeepstheenable
ΔV
+
capacitorCENchargedtothe7.5Vclampvoltage(ortoV ,
−2
+
r 150mV
(
)
150mV
for V < 7.5V). When a fault occurs, CEN is discharged to
⎛
⎞
RSENSE
=
1−
⎜
⎝
⎟
⎠
below the enable low threshold (1.15V typ) which shuts
down both MOSFETs. When the FAULT pin or thermostat
releases, CEN recharges to the upper enable threshold
where restart is attempted. In a sustained short circuit,
FAULT will again pull low and the cycle will repeat until the
short is removed. The time to shut down for a DC input
or thermal fault is given by:
ISC
ΔV
r = current senseratio, ΔV = VGS = VGS − VT
The time for the current to recover to I following the
initial current spike is approximately Q /0.5mA, where
SC
GS
Q
is the MOSFET gate-to-source charge. I need not
GS
SC
be set higher than the required start-up current for mo-
t
= (100 + 0.8R ) C
EN
DC input
SHUTDOWN
F
tors (see Starting High In-Rush Current Loads). Note that
1158fb
14
LT1158
APPLICATIONS INFORMATION
–
Notethatforthefirsteventonly,t
isapproximately
SENSE pin is within 1.2V of supply. Under these condi-
tions the current is limited only by the R in series
SHUTDOWN
twice the above value since C is being discharged all
EN
DS(ON)
the way from its quiescent voltage. Allowable values for
R are from zero to 10k.
F
with R
. For a 5-lead MOSFET the current is limited
SENSE
DS(ON)
by R
alone, since R
is not in the output path
SENSE
(see Figure 7). Again adjusting R
the worst-case start currents are:
for temperature,
DS(ON)
7.5V
1.15V
1.2V
25μA
7.5V
ISTART
=
=
3-Lead MOSFET
5-Lead MOSFET
allows inductive
ENABLE
1+ ∂ R
)+ RSENSE
(
(
)
DS ON
(
+
C
EN
1μF
1.2V
R
F
ISTART
1k
LT1158
1+ ∂ R
)
DS ON
(
)
FAULT
Properly sizing the MOSFET for I
START
loads with long time constants, such as motors with high
mechanical inertia, to be started.
OPTIONAL THERMOSTAT
CLOSE ON RISE
AIRPAX #67FXXX
1158 F09
Returning to the example used in Power MOSFET Selec-
Figure 9. Self-Protection with Auto Restart
tion, an IRFZ34 (R
= 0.05Ω max) was selected for
DS(ON)
operationat5A.Iftheshort-circuitcurrentisalsosetat5A,
what start current can be supported? From the equation
t
becomes more difficult to analyze when the
SHUTDOWN
output is shorted with a PWM input. This is because the
FAULT pin only conducts when fault currents are actually
present in the MOSFET. FAULT does not conduct while the
for R
, a 0.03Ω shunt would be required, allowing
SENSE
the worst-case start current to be calculated:
1.2V
input is low in Figures 6 and 7 or during the interval I
0 in Figure 8. Thus t
the duty cycle of the current in the top MOSFET is low,
maintaining the average MOSFET current at a relatively
constant level.
=
DS
ISTART
=
=10A
will safely increase when
1.7 0.05Ω+0.03Ω
(
)
SHUTDOWN
This calculation gives the minimum current which could
be delivered with the IRFZ34 at T = 125°C without activat-
J
ing the FAULT pin on the LT1158. If more start current is
The length of time following shutdown before restart is
attempted is given by:
required, using an IRFZ44 (R
= 0.028Ω max) would
DS(ON)
increase I
to over 15A at T = 110°C, even though
START
J
⎛
⎜
⎞
⎟
the short-circuit current remains at 5A.
1.5V
⎝ 25μA⎠
tRESTART
=
C = 6×104 C
(
)
EN
EN
In order for the V sensing function to work properly, the
DS
supply pins for the LT1158 must be connected at the drain
of the top MOSFET, which must be properly decoupled
(see Ugly Transient Issues).
In Figure 9, the top MOSFET would shut down after being
in DC current limit for 0.9ms and try to restart at 60ms
intervals, thus producing a duty cyle of 1.5% in short
circuit. The resulting average top MOSFET dissipation
during a short is easily measured by taking the product of
the supply voltage and the average supply current.
Driving Lamps
Incandescent lamps represent a challenging load because
they have much in common with a short circuit when cold.
The top gate driver in the LT1158 can be configured to turn
on large lamps while still protecting the power MOSFET
Starting High In-Rush Current Loads
TheLT1158hasaV sensingfunctionwhichallowsmore
than I to flow in the top MOSFET providing that the
DS
SC
1158fb
15
LT1158
APPLICATIONS INFORMATION
from a true short. This is done by using the current limit to
control cold filament current in conjunction with the self-
protection circuit of Figure 9. The reduced cold filament
current also extends the life of the filament.
down the top MOSFET. The LT1158 will then go into the
automatic restart mode described in Self-Protection with
Automatic Restart above.
The time constant for an incandescent filament is tens
A good guideline is to choose R
to set I at ap-
of milliseconds, which means that t
will have
SENSE
SC
SHUTDOWN
proximately twice the steady state “on” current of the
lamp(s). t is then made long enough to guar-
antee that the lamp filaments heat and drop out of current
limit before the enable capacitor discharges to the enable
low threshold. For a short-circuit, the enable capacitor
will continue to discharge below the threshold, shutting
to be longer than in most other applications. This places
increased SOA demands on the MOSFET during a short
circuit, requiring that a larger than normal device be used.
A protected high current lamp driver application is shown
in Figure 18.
SHUTDOWN
TYPICAL APPLICATIONS
5V TO 10V INPUT (USE LOGIC-LEVEL Q1, Q2)
8V TO 20V INPUT (USE STANDARD Q1, Q2
AND CONNECT BOOST DIODE TO PIN 1)
1N4148
100k
s
16
1
2
3
4
5
6
7
8
+
BOOST DR
BOOST
500μF
Q1
VP0300
LOW ESR
15
14
13
12
11
10
9
+
V
T GATE DR
T GATE FB
T SOURCE
0.01μF
SHORT-CIRCUIT
CURRENT = 8A
INSERT FOR
ZERO POWER
SHUTDOWN
0.1μF
680k
BIAS
L1
R
S
22μH
0.015Ω
+3.3V/6A
OUTPUT
ENABLE
FAULT
INPUT
GND
+
100k
+
–
+
10μF
LT1158
100Ω
2N2222
1000μF
LOW ESR
+
SENSE
CMOS
ON/OFF
100Ω
–
SENSE
Q2
+
V
Q1, Q2: IRLZ44 (LOGIC-LEVEL)
IRFZ44 (STANDARD)
B GATE FB
B GATE DR
1.62k
1%
24k
1N4148
1
510Ω
L1: HURRICANE LAB
HL-KK122T/BB
8
7
6
5
1000pF
0.05μF
1k
2
R : VISHAY/DALE TYPE LVR-3
S
4.99k
1%
VISHAY/ULTRONIX RCS01, SM1
ISOTEK CORP. ISA-PLAN SMR
LT1431
3
4
200pF
CONSTANT OFF TIME CURRENT MODE CONTROL LOOP
1
V
OUT
FREQUENCY =
WHERE t
≈ 10μs
OFF
1 –
(
)
t
V
LT1158 F10
OFF
IN
Figure 10. High Efficiency 3.3V Step-Down Switching Regulator (Requires No Heatsinks)
1158fb
16
LT1158
TYPICAL APPLICATIONS
DRIVER SUPPLY 10V TO 15V
(CAN BE POWERED FROM V
V
4.5V TO 6V
IN
IN
WITH LOGIC-LEVEL Q1, Q2)
0.33μF
16k
0.01μF
+
+
BAS16
10μF
1
220μF
10V
16
15
14
13
12
11
10
9
BOOST DR
BOOST
T GATE DR
T GATE FB
T SOURCE
1
2
3
4
8
7
6
5
OS-CON s 4
2
+
200pF
V
Q1
0.01μF
SHORT-CIRCUIT
CURRENT = 22A
LT1431
0.22μF
3
4.99k
1%
BIAS
500k
L1
R
S
8μH
+
–
4
V
OUT
ENABLE
FAULT
SHUTDOWN
3.3k
15A
LT1158
+
0.01Ω
EA
5
6
7
8
330μF
6.3V
AVX s 4
+
SENSE
1000pF
1
2
3
4
8
7
6
5
–
INPUT
SENSE
470pF
+
GND
V
CMOS
555
24k
R
X
Q2
B GATE FB
B GATE DR
1%
LT1158 F11
L1: COILTRONICS CTX02-12171-1
S
Q1, Q2: MTB75N05HD (USE WITH 10V TO 15V DRIVER SUPPLY)
V
R
2.90V 3.05V 3.30V 3.45V 3.60V
(1%) 806Ω 1.10k 1.62k 1.91k 2.21k
OUT
R : KRL/BANTRY SL-1R010J s 2
MTB75N03HDL (USE WITH V DRIVER SUPLY)
IN
X
CMOS 555: LMC555 OR TLC555
Figure 11. 5V to 3.XXV,15A Converter (Uses PC Board Area for Heatsink)
8V TO 20V INPUT
1N4148
100k
s
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
+
BOOST DR
BOOST
500μF
IRFZ34
510k
VP0300
LOW ESR
+
V
T GATE DR
T GATE FB
T SOURCE
SHORT-CIRCUIT
CURRENT = 6A
0.01μF
INSERT FOR
ZERO POWER
SHUTDOWN
BIAS
0.1μF
L1
50μH
R
S
20mΩ
+5V/4A
OUTPUT
ENABLE
FAULT
INPUT
GND
+
100k
+
–
10μF
+
LT1158
2N2222
100Ω
100Ω
1000μF
+
SENSE
CMOS
ON/OFF
LOW ESR
–
SENSE
IRFZ44
1N4148
+
V
B GATE FB
B GATE DR
24k
510Ω
L1: COILTRONICS
CTX50-5-52
1
2
3
4
8
7
6
5
1000pF
0.05μF
1k
R : VISHAY/DALE TYPE LVR-3
S
VISHAY/ULTRONIX RCS01, SM1
ISOTEK CORP. ISA-PLAN SMR
LT1431
CONSTANT OFF TIME CURRENT MODE CONTROL LOOP
SEE FIGURE 4 FOR EFFICIENCY CURVE
1
V
OUT
FREQUENCY =
WHERE t
≈ 10μs
OFF
1 –
(
)
LT1158 F12
t
V
OFF
IN
Figure 12. High Efficiency 5V Step-Down Switching Regulator (Requires No Heatsinks)
1158fb
17
LT1158
TYPICAL APPLICATIONS
INPUT
30V MAX
SHUTDOWN
4.7k
0.01μF
1N4148
4.7k
1μF
+
+
500μF EA
LOW ESR
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
1
2
16
15
14
13
12
11
10
9
BOOST DR
BOOST
0.1μF
IRFZ44
330k
*
3.4k
+
V
T GATE DR
T GATE FB
T SOURCE
SHORT-CIRCUIT
CURRENT = 15A
+
0.01μF
0.1μF
10μF
3
EXT
BIAS
L1
R
SYNC
S
30k
70μH
0.007Ω
4
5
6
7
8
5V OR
12V*
1N4148
1N4148
ENABLE
FAULT
INPUT
GND
f = 25kHz
0.01μF
+
–
+
2.2nF
LT3525
LT1158
+
SENSE
1000μF
LOW ESR
–
SENSE
27k
1μF
(2) IRFZ44
+
V
*
330pF
510Ω
10k
B GATE FB
B GATE DR
MBR340
LT1158 F13
* ADD THESE COMPONENTS TO IMPLEMENT
LOW-DROPOUT 12V REGULATOR
L1: MAGNETICS CORE #55585-A2
30 TURNS 14GA MAGNET WIRE
R : DALE TYPE LVR-3
S
ULTRONIX RCS01
Figure 13. 90% Efficiency 24V to 5V 10A Switching Regulator
95% Efficiency 24V to 12V 10A Low Dropout Switching Regulator
MOTOR SPEED
0 TO 100%
10V TO 30V
5.1k
1N4148
10k
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
+
1N5231A
10μF
BOOST DR
BOOST
T GATE DR
T GATE FB
T SOURCE
0.1μF
+
1μF
7.5k
1000μF
24Ω
+
LOW ESR
V
0.01μF
1k
+
Q1
BIAS
0.33μF
510Ω
1
2
3
4
8
7
6
5
ENABLE
FAULT
INPUT
GND
START CURRENT
= 15A MINIMUM
+
–
LT1158
+
SENSE
CMOS
555
0.02Ω
13k
–
SENSE
2.2nF
+
V
Q2
24Ω
-
B GATE FB
B GATE DR
THE CMOS 555 IS USED AS A 25kHz TRIANGLE-WAVE
OSCILLATOR DRIVING THE LT1158 INPUT PIN. THE
D.C. LEVEL OF THE TRIANGLE WAVE IS SET BY THE
POTENTIOMETER ON THE CMOS 555 SUPPLY PIN, AND
ALLOW ADJUSTMENT OF THE LT1158 DUTY CYCLE
FROM 0 TO 100%.
CMOS 555: LMC555 OR TLC555
Q1, Q2: MTP35N06E
LT1158 F14
Figure 14. Potentiometer-Adjusted Open Loop Motor Speed Control with Short-Circuit Protection
1158fb
18
LT1158
TYPICAL APPLICATIONS
7.2V
NOMINAL
+
BAT85
100μF
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
BOOST DR
BOOST
T GATE DR
T GATE FB
T SOURCE
15Ω
0.1μF
+
V
+
0.01μF
1k
10μF
BIAS
Q1
1N4148
STOP
(FREE RUN)
ENABLE
FAULT
INPUT
GND
START CURRENT
= 25A MINIMUM
+
+
–
LT1158
1μF
+
SENSE
R
S
0.015Ω
–
PWM
SENSE
+
V
15Ω
-
Q2
B GATE FB
B GATE DR
LT1158 F15
Q1, Q2: IRLZ44 (LOGIC-LEVEL)
R : DALE TYPE LVR-3
S
ULTRONIX RCS01
Figure 15. High Efficiency 6-Cell NiCd Protected Motor Drive
+
+
+
V
V
V
LT1158
ENABLE
LT1158
ENABLE
LT1158
ENABLE
F
A
FAULT
FAULT
F
FAULT
F
C
B
INPUT
INPUT
INPUT
5V
SHUTDOWN
POSITION FEEDBACK
CONTROLS LT1158
ENABLE INPUTS
COMMUTATING LOGIC
PWM CONTROLS
LT1158 INPUTS
1158 F16
Figure 16. 3-Phase Brushless DC Motor Control
1158fb
19
LT1158
TYPICAL APPLICATIONS
1N4148
10V TO 30V
470μF
1
16
15
14
13
12
11
10
9
BOOST DR
BOOST
0.1μF
15Ω
D1
2
+
SIDE A: SHOWS
STANDARD MOSFET
CONNECTION
+
V
T GATE DR
T GATE FB
T SOURCE
Q1
0.01μF
3
LOW
ESR
BIAS
4
ENABLE A
FAULT A
INPUT A
ENABLE
FAULT
+
+
10μF
LT1158
5
6
7
8
+
SENSE
R
S
0.015Ω
–
INPUT
SENSE
–
Q2
+
GND
V
2.4k
15Ω
B GATE FB
B GATE DR
1N4148
+
-
1
16
15
14
13
12
11
10
9
470μF
LOW
ESR
BOOST DR
BOOST
Q3
15Ω
SIDE B: SHOWS
CURRENT-SENSING
MOSFET CONNECTION
2
3
4
5
6
7
8
+
V
T GATE DR
T GATE FB
T SOURCE
0.01μF
0.1μF
D2
BIAS
+
–
ENABLE B
ENABLE
FAULT
INPUT
GND
+ 10μF
LT1158
2.4k
+
SENSE
FAULT B
INPUT B
47Ω
15Ω
–
SENSE
Q4
Q1, Q3: IRF540 (STANDARD)
IRC540 (SENSE FET)
Q2, Q4: IRFZ44
+
V
D1, D2: BAT83
B GATE FB
B GATE DR
R : DALE TYPE LVR-3
S
ULTRONIX RCS01
LT1158 F17a
Control Logic for Locked Anti-Phase Drive
Motor stops if either side is shorted to ground
Control Logic for Sign/Magnitude Drive
5V
5.1k
ENABLE A
ENABLE A
FAULT A
INPUT A
0.01μF
74HC132
74HC02
FAULT A
INPUT A
PWM
PWM
DIRECTION
1N4148
ENABLE B
150k
STOP
ENABLE B
(FREE RUN)
+
FAULT B
0.1μF
FAULT B
1μF
1N4148
INPUT B
INPUT B
1158F17b
1158F17c
Figure 17. 10A Full Bridge Motor Control
1158fb
20
LT1158
PACKAGE DESCRIPTION
N Package
16-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
.770*
(19.558)
MAX
14
12
10
9
8
15
13
11
16
.255 .015*
(6.477 0.381)
2
1
3
4
6
5
7
.300 – .325
(7.620 – 8.255)
.130 .005
(3.302 0.127)
.045 – .065
(1.143 – 1.651)
.020
(0.508)
MIN
.065
(1.651)
TYP
.008 – .015
(0.203 – 0.381)
+.035
–.015
.325
.120
(3.048)
MIN
.018 .003
(0.457 0.076)
.100
(2.54)
BSC
+0.889
8.255
(
)
–0.381
NOTE:
INCHES
MILLIMETERS
1. DIMENSIONS ARE
N16 1002
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
SW Package
16-Lead Plastic Small Outline (Wide .300 Inch)
(Reference LTC DWG # 05-08-1620)
.050 BSC .045 .005
.398 – .413
.030 .005
TYP
(10.109 – 10.490)
NOTE 4
15 14
12
10
9
N
16
N
13
11
.325 .005
.420
MIN
.394 – .419
(10.007 – 10.643)
NOTE 3
N/2
8
1
2
3
N/2
RECOMMENDED SOLDER PAD LAYOUT
2
3
5
7
1
4
6
.291 – .299
(7.391 – 7.595)
NOTE 4
.037 – .045
(0.940 – 1.143)
.093 – .104
(2.362 – 2.642)
.010 – .029
× 45°
(0.254 – 0.737)
.005
(0.127)
RAD MIN
0° – 8° TYP
.050
(1.270)
BSC
.004 – .012
.009 – .013
(0.102 – 0.305)
NOTE 3
(0.229 – 0.330)
.014 – .019
.016 – .050
(0.356 – 0.482)
TYP
(0.406 – 1.270)
NOTE:
1. DIMENSIONS IN
INCHES
(MILLIMETERS)
S16 (WIDE) 0502
2. DRAWING NOT TO SCALE
3. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS.
THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS
4. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
1158fb
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
21
LT1158
TYPICAL APPLICATION
12V
1N4148
+
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
1000μF
BOOST DR
BOOST
IRCZ44
+
V
T GATE DR
T GATE FB
T SOURCE
+
0.01μF
6.2k
10μF
0.1μF
BIAS
+
–
ENABLE
FAULT
INPUT
GND
+
10μF
LT1158
12V
55W
+
MBR330
SENSE
51Ω
–
ON/OFF
SENSE
+
V
B GATE FB
B GATE DR
I
t
t
: 10A
SC
SHUTDOWN
= 50ms
= 600ms
LT1158 F18
RESTART
Figure 18. High Current Lamp Driver with Short-Circuit Protection
1158fb
LT 0309 REV B • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
22
●
●
© LINEAR TECHNOLOGY CORPORATION 1994
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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