SC1173CSWTR [SEMTECH]
Switching Controller, Voltage-mode, 1A, 220kHz Switching Freq-Max, BIPolar, PDSO24, MS-013AD, SOIC-24;型号: | SC1173CSWTR |
厂家: | SEMTECH CORPORATION |
描述: | Switching Controller, Voltage-mode, 1A, 220kHz Switching Freq-Max, BIPolar, PDSO24, MS-013AD, SOIC-24 转换器 稳压器 控制器 |
文件: | 总12页 (文件大小:121K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com
DESCRIPTION
FEATURES
The SC1172/3 combines a synchronous voltage mode
controller with a low-dropout linear regulator providing
most of the circuitry necessary to implement two DC/DC
converters for powering advanced microprocessors such
as Pentium® II (Klamath) or Deschutes.
•
•
•
•
•
Synchronous design, enables no heatsink solution
95% efficiency (switching section)
5 bit DAC for output programmability
On chip power good function
Designed for Intel Pentium® II VRM8.1 require-
ments
The SC1172/3 switching section features an integrated 5
bit D/A converter, pulse by pulse current limiting,
integrated power good signaling, and logic compatible
shutdown. The SC1172/3 switching section operates at
a fixed frequency of 200kHz, providing an optimum
compromise between size, efficiency and cost in the
intended application areas. The integrated D/A con-
verter provides programmability of output voltage from
2.0V to 3.5V in 100mV increments and 1.30V to 2.05V
in 50mV increments with no external components.
•
1.5V or Adj. @ 1% for linear section
APPLICATIONS
•
•
•
•
Pentium® ll or Deschutes microprocessor supplies
Flexible motherboards
1.3V to 3.5V microprocessor supplies
Programmable dual power supplies
ORDERING INFORMATION
The SC1172/3 linear section is a high performance
positive voltage regulator design for either the GTL bus
supply at 1.5V (SC1172) or an adjustable output
(SC1173).
Linear
Temp.
Part Number(1) Package
Voltage
Range (TJ)
SC1172CSW SO-24
SC1173CSW SO-24
Note:
1.5V
0° to 125°C
0° to 125°C
The output of the linear regulator can provide up to 5A or
more with the appropriate external MOSFET.
Adj.
(1) Add suffix ‘TR’ for tape and reel.
BLOCK DIAGRAM
PIN CONFIGURATION
EN
VCC CS- CS+
BSTH
Top View
CURRENT LIMIT
1.25 REF
VCC
LEVEL SHIFT
DH
AND HIGH SIDE
MOSFET DRIVE
70mV
AGND
1
2
3
4
5
6
24
23
22
21
20
19
18
17
16
15
14
13
GATE
LDOV
VID0
VID1
VID2
VID3
VID4
VOSENSE
EN
VID4
VID3
VID2
VID1
VID0
D/A &
NC
NC
SHUT-
DOWN
LOGIC
R
PGNDH
Q
OSCILLATOR
LDOS
VCC
OVP
S
PWRGOOD
CS-
7
VOSENSE
SHOOT-
THRU
CONTROL
OPEN
COLLECTORS
8
CS+
9
PWRGOOD
PGNDH
10
BSTH
BSTL
DL
BSTL
DL
ERROR
AMP
VCC
DH
11
12
SYNCHRONOUS
MOSFET DRIVER
PGNDL
OVP
PGNDL
(24 Pin SOIC)
AGND
FET
CONTROLLER
1.25V
REF
LDOV
GATE
LDOS
1
Pentium is a registered trademark of Intel Corporation
© 1999 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
ABSOLUTE MAXIMUM RATINGS
Parameter
Symbol
Maximum
-0.3 to +7
Units
VCC to GND
VIN
V
V
PGND to GND
± 1
BST to GND
-0.3 to +15
0 to +70
V
Operating Temperature Range
TA
TJ
°C
Junction Temperature Range
0 to +125
-65 to +150
300
°C
Storage Temperature Range
TSTG
TL
°C
Lead Temperature (Soldering) 10 seconds
Thermal Impedance Junction to Ambient
Thermal Impedance Junction to Case
°C
80
θJA
θJC
°C/W
°C/W
25
ELECTRICAL CHARACTERISTICS
Unless specified: VCC = 4.75V to 5.25V; GND = PGND = 0V; VOSENSE = VO; 0mV < (CSp-CSm) < 60mV; LDOV = 11.4V to 12.6V; TA = 25oC
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Switching Section
Output Voltage
IO = 2A
See Note 1.
Supply Voltage
VCC
4.2
7
V
mA
%
Supply Current
VCC = 5.0
IO = 0.8A to 15A
8
1
15
Load Regulation
Line Regulation
0.5
%
Minimum operating voltage
Current Limit Voltage
Oscillator Frequency
Oscillator Max Duty Cycle
DH Sink/Source Current
DL Sink/Source Current
Output Voltage Tempco
Gain (AOL)
4.2
80
V
60
180
90
1
70
200
95
mV
kHz
%
220
BSTH-DH = 4.5V, DH-PGNDH = 2V
BSTL-DL = 4.5V, DL-PGNDL = 2V
A
1
A
30
35
100 ppm/oC
VOSENSE to VO
VOVP = 3.0V
dB
%
OVP threshold voltage
OVP source current
Power good threshold voltage
Dead time
120
10
88
50
mA
112
5
%
100
ns
Linear Section
Quiescent current
LDOV = 12V
mA
V
Output Voltage (SC1172)
Reference Voltage (SC1173)
Feedback Pin Bias Current (SC1173)
Gain (AOL)
1.485 1.500 1.515
1.252 1.265 1.278
V
10
uA
dB
%
LDOS to GATE
IO = 0 to 8A(2)
90
0.3
0.3
200
Load Regulation
Line Regulation
%
Output Impedance
Ω
Notes: (1) See Output Voltage table
(2) In application circuit
2
© 1999 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
PIN DESCRIPTION
Pin Pin Name
Pin Function
1
2
3
4
5
6
7
AGND
NC
Small Signal Analog and Digital Ground
No connection
Top View
NC
No Connection
LDOS
VCC
OVP
Sense Input for LDO
AGND
1
2
3
4
5
6
24
23
22
21
20
19
18
17
16
15
14
13
GATE
LDOV
VID0
VID1
VID2
VID3
VID4
VOSENSE
EN
NC
NC
Input Voltage
High Signal out if VO>setpoint +20%
LDOS
VCC
OVP
PWRGOOD(1) Open collector logic output, high if VO
within 10% of setpoint
PWRGOOD
CS-
7
8
9
CS-
Current Sense Input (negative)
Current Sense Input (positive)
Power Ground for High Side Switch
High Side Driver Output
8
CS+
9
CS+
PGNDH
10
BSTH
BSTL
DL
10 PGNDH
11 DH
DH
11
12
PGNDL
12 PGNDL
13 DL
Power Ground for Low Side Switch
Low Side Driver Output
(24 Pin SOIC)
14 BSTL
15 BSTH
16 EN(1)
Supply for Low Side Driver
Supply for High Side Driver
Logic low shuts down the converter;
High or open for normal operation.
17 VOSENSE
18 VID4(1)
19 VID3(1)
20 VID2(1)
21 VID1(1)
22 VID0(1)
23 LDOV
24 GATE
Top end of internal feedback chain
Programming Input (MSB)
Programming Input
Programming Input
Programming Input
Note:
Programming Input (LSB)
+12V for LDO section
Gate Drive Output LDO
(1) All logic level inputs and outputs are open
collector TTL compatible.
3
© 1999 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
OUTPUT VOLTAGE
Unless specified: VCC = 4.75V to 5.25V; GND = PGND = 0V; VOSENSE = VO; 0mV < (CSp-CSm) < 60mV; TA = 25oC
PARAMETER
CONDITIONS
VID
MIN
TYP
MAX
1.313
UNITS
43210
01111
01110
Output Voltage
IO = 2A in Application Circuit
1.287
1.300
V
1.336
1.386
1.435
1.485
1.534
1.584
1.633
1.683
1.732
1.782
1.831
1.881
1.930
1.980
2.029
1.980
2.079
2.178
2.277
2.376
2.475
2.574
2.673
2.772
2.871
2.970
3.069
3.168
3.267
3.366
3.465
1.350
1.400
1.450
1.500
1.550
1.600
1.650
1.700
1.750
1.800
1.850
1.900
1.950
2.000
2.050
2.000
2.100
2.200
2.300
2.400
2.500
2.600
2.700
2.800
2.900
3.000
3.100
3.200
3.300
3.400
3.500
1.364
1.414
1.465
1.515
1.566
1.616
1.667
1.717
1.768
1.818
1.869
1.919
1.970
2.020
2.071
2.020
2.121
2.222
2.323
2.424
2.525
2.626
2.727
2.828
2.929
3.030
3.131
3.232
3.333
3.434
3.535
01101
01100
01011
01010
01001
01000
00111
00110
00101
00100
00011
00010
00001
00000
11111
11110
11101
11100
11011
11010
11001
11000
10111
10110
10101
10100
10011
10010
10001
10000
4
© 1999 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
APPLICATION CIRCUIT
5
© 1999 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
MATERIALS LIST
Qty. Reference
Part/Description
Vendor
Notes
4
6
3
C1,C5,C13,C 0.1µF Ceramic
18
Various
C2,C3,C14- 1500µF/6.3V
C17
SANYO
Various
MV-GX or equiv. Low ESR
C11,C12,
C21
330µF/6.3V
1
3
L1
4µH
8 Turns 16AWG on MICROMETALS T50-52D core
Q1,Q2,Q3
See notes
See notes
FET selection requires trade-off between efficiency and
cost. Absolute maximum RDS(ON) = 22 mΩ for Q1,Q2
1
1
1
1
1
1
1
1
R4
IRC
OAR-1 Series
5mΩ
R5
Various
Various
Various
Various
Various
Various
SEMTECH
2.32kΩ, 1%, 1/8W
1kΩ, 1%, 1/8W
10Ω, 5%, 1/8W
1%, 1/8W
R6
R1
R12
R13
R17
U1
See Table (Not required for SC1172)
See Table (Not required for SC1172)
1%, 1/8W
100K, 5% 1/8W
SC1172/3CSW
SETTING LDO OUTPUT VOLTAGE
1.265 (RA + RB )
RB
RA
VOUT
=
+ (IFB RA )
RB
VO LDO
3.45V
3.30V
3.10V
2.90V
2.80V
2.50V
1.50V
R12
R13
Where :
105Ω
105Ω
102Ω
100Ω
100Ω
100Ω
100Ω
182Ω
169Ω
147Ω
130Ω
121Ω
97.6Ω
18.7Ω
IFB = Feedback pin bias current
RA = Top feedback resistor
RB = Bottom feedback resistor
See layout diagram for clarification
RA andRB must be low enough so
that the (IFB RA ) term does not cause
significant error
6
© 1999 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
95%
90%
85%
80%
95%
90%
85%
80%
2.8V Std
3.5V Std
2.8V Sync
3.5V Sync
2.8V Sync Lo Rds
75%
3.5V Sync Lo Rds
75%
70%
70%
0
2
4
6
8
10
12
14
16
0
2
4
6
8
10
12
14
16
Io (Amps)
Io (Amps)
Typical Efficiency at Vo=3.5V
Typical Efficiency at Vo=2.8V
95%
95%
90%
85%
90%
85%
80%
80%
2.0V Std
2.0V Sync
2.5V Std
2.5V Sync
2.0V Sync Lo Rds
75%
2.5V Sync Lo Rds
75%
70%
70%
0
2
4
6
8
10
12
14
16
0
2
4
6
8
10
12
14
16
Io (Amps)
Io (Amps)
Typical Efficiency at Vo=2.5V
Typical Efficiency at Vo=2.0V
Typical Ripple, Vo=2.8V, Io=10A
© 1999 SEMTECH CORP.
Transient Response Vo=2.8V, Io=300mA to 10A
7
652 MITCHELL ROAD NEWBURY PARK CA 91320
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
as small as possible. This loop contains all the high cur-
rent, fast transition switching. Connections should be as
wide and as short as possible to minimize loop induc-
tance. Minimizing this loop area will a) reduce EMI, b)
lower ground injection currents, resulting in electrically
“cleaner” grounds for the rest of the system and c) mini-
mize source ringing, resulting in more reliable gate
switching signals.
LAYOUT GUIDELINES
Careful attention to layout requirements are necessary
for successful implementation of the SC1172/3 PWM
controller. High currents switching at 200kHz are pre-
sent in the application and their effect on ground plane
voltage differentials must be understood and mini-
mized.
1). The high power parts of the circuit should be laid out
first. A ground plane should be used, the number and
position of ground plane interruptions should be such
as to not unnecessarily compromise ground plane in-
tegrity. Isolated or semi-isolated areas of the ground
plane may be deliberately introduced to constrain
ground currents to particular areas, for example the in-
put capacitor and bottom FET ground.
3). The connection between the junction of Q1, Q2 and
the output inductor should be a wide trace or copper
region. It should be as short as practical. Since this
connection has fast voltage transitions, keeping this
connection short will minimize EMI. The connection be-
tween the output inductor and the sense resistor should
be a wide trace or copper area, there are no fast volt-
age or current transitions in this connection and length
is not so important, however adding unnecessary
impedance will reduce efficiency.
2). The loop formed by the Input Capacitor(s) (Cin), the
Top FET (Q1) and the Bottom FET (Q2) must be kept
12V IN
5V
10
1
2
24
23
22
21
20
19
18
17
16
15
14
13
AGND
NC
GATE
LDOV
VID0
2.32k
3
NC
Cin
+
4
Q1
Q2
1.00k
LDOS
VCC
VID1
0.1uF
0.1uF
5
5mOhm
Cout
VID2
Vout
6
OVP
VID3
4uH
+
7
PWRGOOD
CS-
VID4
8
VO SENSE
EN
9
CS+
10
11
12
PGNDH
DH
BSTH
BSTL
DL
PGNDL
SC1172/3
RA
Heavy lines indicate
high current paths.
5V
Vo Lin
Q3
+
+
RB
Cout Lin
Cin Lin
For SC1172, RA and RB
are not required. LDOS connects to
Vo Lin
Layout diagram for the SC1172/3
8
© 1999 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
4) The Output Capacitor(s) (Cout) should be located
as close to the load as possible, fast transient load
currents are supplied by Cout only, and connections
between Cout and the load must be short, wide cop-
per areas to minimize inductance and resistance.
5V supply through a 10Ω resistor, the Vcc pin should
be decoupled directly to AGND by a 0.1µF ceramic
capacitor, trace lengths should be as short as possi-
ble.
7) The Current Sense resistor and the divider across
it should form as small a loop as possible, the traces
running back to CS+ and CS- on the SC1172/3 should
run parallel and close to each other. The 0.1µF ca-
pacitor should be mounted as close to the CS+ and
CS- pins as possible.
5) The SC1172/3 is best placed over a quite ground
plane area, avoid pulse currents in the Cin, Q1, Q2
loop flowing in this area. PGNDH and PGNDL should
be returned to the ground plane close to the package.
The AGND pin should be connected to the ground
side of (one of) the output capacitor(s). If this is not
possible, the AGND pin may be connected to the
ground path between the Output Capacitor(s) and the
Cin, Q1, Q2 loop. Under no circumstances should
AGND be returned to a ground inside the Cin, Q1, Q2
loop.
8) Ideally, the ground for the LDO section should be
returned to the ground side of (one of) the switching
section output capacitor(s).
6) Vcc for the SC1172/3 should be supplied from the
5V
+
Vout
+
Currents in various parts of the power section
9
© 1999 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
fast enough to reduce the voltage dropped across the
ESR at a faster rate than the capacitor sags, hence en-
suring a good recovery from transient with no additional
excursions.
We must also be concerned with ripple current in the
output inductor and a general rule of thumb has been to
allow 10% of maximum output current as ripple current.
Note that most of the output voltage ripple is produced
by the inductor ripple current flowing in the output capac-
itor ESR. Ripple current can be calculated from:
COMPONENT SELECTION
SWITCHING SECTION
OUTPUT CAPACITORS - Selection begins with the
most critical component. Because of fast transient load
current requirements in modern microprocessor core
supplies, the output capacitors must supply all transient
load current requirements until the current in the output
inductor ramps up to the new level. Output capacitor
ESR is therefore one of the most important criteria. The
maximum ESR can be simply calculated from:
V
IN
IL
=
Vt
RIPPLE
4 L fOSC
RESR
≤
It
Ripple current allowance will define the minimum permit-
ted inductor value.
Where
Vt = Maximum transient voltage excursion
It = Transient current step
POWER FETS - The FETs are chosen based on several
criteria with probably the most important being power
dissipation and power handling capability.
TOP FET - The power dissipation in the top FET is a
combination of conduction losses, switching losses and
bottom FET body diode recovery losses.
For example, to meet a 100mV transient limit with a
10A load step, the output capacitor ESR must be less
than 10mΩ. To meet this kind of ESR level, there are
three available capacitor technologies:
a) Conduction losses are simply calculated as:
P
COND = IO2 RDS(on)
δ
Each Capacitor
Total
Technology
C
ESR Qty.
C
ESR
(mΩ)
where
(µF)
Rqd. (µF)
(mΩ)
60
VO
δ =dutycycle≈
Low ESR Tantalum
OS-CON
330
6
3
5
2000
990
10
8.3
8.8
V
IN
330
25
44
b) Switching losses can be estimated by assuming a
switching time, if we assume 100ns then:
Low ESR Aluminum
1500
7500
The choice of which to use is simply a cost /perfor-
mance issue, with Low ESR Aluminum being the
cheapest, but taking up the most space.
PSW = IO VIN 10−2
or more generally,
INDUCTOR - Having decided on a suitable type and
value of output capacitor, the maximum allowable
value of inductor can be calculated. Too large an in-
ductor will produce a slow current ramp rate and will
cause the output capacitor to supply more of the tran-
sient load current for longer - leading to an output volt-
age sag below the ESR excursion calculated above.
The maximum inductor value may be calculated from:
IO
V
(tr + tf ) fOSC
IN
PSW
=
4
c) Body diode recovery losses are more difficult to esti-
mate, but to a first approximation, it is reasonable to as-
sume that the stored charge on the bottom FET body
diode will be moved through the top FET as it starts to
turn on. The resulting power dissipation in the top FET
will be:
RESR
C
L ≤
(
V − VO
)
IN
PRR = QRR VIN fOSC
It
The calculated maximum inductor value assumes 100% To a first order approximation, it is convenient to only
duty cycle, so some allowance must be made. Choosing consider conduction losses to determine FET suitability.
an inductor value of 50 to 75% of the calculated maxi-
mum will guarantee that the inductor current will ramp
For a 5V in; 2.8V out at 14.2A requirement, typical FET
losses would be:
10
652 MITCHELL ROAD NEWBURY PARK CA 91320
© 1999 SEMTECH CORP.
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
INPUT CAPACITORS - since the RMS ripple current in
the input capacitors may be as high as 50% of the out-
put current, suitable capacitors must be chosen ac-
cordingly. Also, during fast load transients, there may
be restrictions on input di/dt. These restrictions require
useable energy storage within the converter circuitry,
either as extra output capacitance or, more usually,
additional input capacitors. Choosing low ESR input
capacitors will help maximize ripple rating for a given
size.
FET type
PD (W) Package
DS(on) (mΩ)
R
BUK556H 22
2.48
0.79
1.53
TO220
D2PAK
SO-8
IRL2203
Si4410
7.0
13.5
BOTTOM FET - Bottom FET losses are almost entirely
due to conduction. The body diode is forced into conduc-
tion at the beginning and end of the bottom switch con-
duction period, so when the FET turns on and off, there
is very little voltage across it, resulting in low switching
losses. Conduction losses for the FET can be deter-
mined by:
PCOND = IO2 RDS(on) (1− δ)
For the example above:
FET type
PD (W) Package
DS(on) (mΩ)
R
BUK556H 22
1.95
0.62
1.20
TO220
D2PAK
SO-8
IRL2203
Si4410
7.0
13.5
Each of the package types has a characteristic thermal
impedance, for the TO-220 package, thermal impedance
is mostly determined by the heatsink used. For the sur-
face mount packages on double sided FR4, 2 oz printed
circuit board material, thermal impedances of 40oC/W
for the D2PAK and 80oC/W for the SO-8 are readily
achievable. The corresponding temperature rise is de-
tailed below:
Temperature rise (oC)
FET type Top FET
BUK556H 49.6(1)
Bottom FET
39.0(1)
24.8
96
IRL2203
Si4410
31.6
122.4
(1) With 20oC/W Heatsink
It is apparent that single SO-8 Si4410 are not adequate for
this application, but by using parallel pairs in each posi-
tion, power dissipation will be approximately halved and
temperature rise reduced by a factor of 4.
11
© 1999 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER WITH LOW DROPOUT
REGULATOR CONTROLLER
SC1172/3
October 25, 1999
OUTLINE DRAWING
JEDEC MS-013AD
B17104B
ECN99-667
12
652 MITCHELL ROAD NEWBURY PARK CA 91320
© 1999 SEMTECH CORP.
相关型号:
SC1173CSWTRT
Switching Controller, Voltage-mode, 220kHz Switching Freq-Max, PDSO24, MS-013AD, SOIC-24
SEMTECH
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