LT1934IDCB-1
更新时间:2024-09-18 14:17:26
品牌:Linear
描述:IC 0.16 A SWITCHING REGULATOR, PDSO6, 2 X 3 MM, 0.80 MM HEIGHT, PLASTIC, MO-229, DFN-6, Switching Regulator or Controller
LT1934IDCB-1 概述
IC 0.16 A SWITCHING REGULATOR, PDSO6, 2 X 3 MM, 0.80 MM HEIGHT, PLASTIC, MO-229, DFN-6, Switching Regulator or Controller 开关式稳压器或控制器
LT1934IDCB-1 规格参数
是否无铅: | 含铅 | 是否Rohs认证: | 不符合 |
生命周期: | Transferred | 零件包装代码: | SON |
包装说明: | HVSON, SOLCC6,.12,20 | 针数: | 6 |
Reach Compliance Code: | not_compliant | ECCN代码: | EAR99 |
HTS代码: | 8542.39.00.01 | 风险等级: | 5.08 |
模拟集成电路 - 其他类型: | SWITCHING REGULATOR | 控制模式: | CURRENT-MODE |
最大输入电压: | 34 V | 最小输入电压: | 4 V |
标称输入电压: | 10 V | JESD-30 代码: | R-PDSO-N6 |
JESD-609代码: | e0 | 长度: | 3 mm |
湿度敏感等级: | 1 | 功能数量: | 1 |
端子数量: | 6 | 最高工作温度: | 125 °C |
最低工作温度: | -40 °C | 最大输出电流: | 0.16 A |
封装主体材料: | PLASTIC/EPOXY | 封装代码: | HVSON |
封装等效代码: | SOLCC6,.12,20 | 封装形状: | RECTANGULAR |
封装形式: | SMALL OUTLINE, HEAT SINK/SLUG, VERY THIN PROFILE | 峰值回流温度(摄氏度): | 235 |
认证状态: | Not Qualified | 座面最大高度: | 0.8 mm |
子类别: | Switching Regulator or Controllers | 表面贴装: | YES |
切换器配置: | BUCK | 技术: | BIPOLAR |
温度等级: | AUTOMOTIVE | 端子面层: | Tin/Lead (Sn/Pb) |
端子形式: | NO LEAD | 端子节距: | 0.5 mm |
端子位置: | DUAL | 处于峰值回流温度下的最长时间: | 20 |
宽度: | 2 mm | Base Number Matches: | 1 |
LT1934IDCB-1 数据手册
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PDF下载LT1934/LT1934-1
Micropower Step-Down
Switching Regulators
in ThinSOT and DFN
FEATURES
DESCRIPTION
TheLT®1934isamicropowerstep-downDC/DCconverter
with internal 400mA power switch, packaged in a low
profile (1mm) ThinSOT. With its wide input range of 3.2V
to 34V, the LT1934 can regulate a wide variety of power
sources, from 4-cell alkaline batteries and 5V logic rails
to unregulated wall transformers and lead-acid batteries.
Quiescent current is just 12μA and a zero current shut-
down mode disconnects the load from the input source,
simplifying power management in battery-powered sys-
tems. Burst Mode® operation and the low drop internal
power switch result in high efficiency over a broad range
of load current.
n
Wide Input Voltage Range: 3.2V to 34V
Micropower Operation: I = 12μA
n
Q
n
n
n
n
n
n
n
5V at 250mA from 6.5V to 34V Input (LT1934)
5V at 60mA from 6.5V to 34V Input (LT1934-1)
3.3V at 250mA from 4.5V to 34V Input (LT1934)
3.3V at 60mA from 4.5V to 34V Input (LT1934-1)
Low Shutdown Current: <1μA
Low V
Switch: 200mV at 300mA
CESAT
Low Profile (1mm) SOT-23 (ThinSOT™) and
(2mm × 3mm × 0.8mm) 6-Pin DFN Package
APPLICATIONS
The LT1934 provides up to 300mA of output current. The
LT1934-1 has a lower current limit, allowing optimum
choice of external components when the required output
current is less than 60mA. Fast current limiting protects
the LT1934 and external components against shorted
outputs, even at 34V input.
n
Wall Transformer Regulation
n
Automotive Battery Regulation
n
Standby Power for Portable Products
Distributed Supply Regulation
Industrial Control Supplies
n
n
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
3.3V Step-Down Converter
Efficiency
100
D2
LT1934
IN
V
= 12V
90
80
70
60
50
0.22μF
BOOST
L1
V
= 5V
47μH
OUT
V
OUT
V
IN
V
IN
SW
3.3V
4.5V TO 34V
250mA
C2
2.2μF
V
OUT
= 3.3V
D1
LT1934
10pF
1M
+
C1
100μF
ON OFF
SHDN
GND
FB
604k
C1: SANYO 4TPB100M
1934 TA01
0.1
1
10
100
C2: TAIYO YUDEN GMK325BJ225MN
D1: ON SEMICONDUCTOR MBR0540
D2: CENTRAL CMDSH-3
LOAD CURRENT (mA)
1934 TA02
L1: SUMIDA CDRH4D28-470
1934fe
1
LT1934/LT1934-1
(Note 1)
ABSOLUTE MAXIMUM RATINGS
Input Voltage (V )................................................... 34V
Operating Temperature Range (Note 2)
IN
BOOST Pin Voltage ................................................. 40V
BOOST Pin Above SW Pin........................................ 20V
SHDN Pin................................................................. 34V
FB Voltage.................................................................. 6V
LT1934E/LT1934E-1.............................–40°C to 85°C
LT1934I/LT1934I-1.............................–40°C to 125°C
Maximum Junction Temperature .......................... 125°C
Storage Temperature Range...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)
SW Voltage ............................................................... V
IN
TSOT-23............................................................ 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
6
5
4
FB
BOOST
SW
1
2
3
BOOST 1
GND 2
FB 3
6 SW
5 V
7
GND
SHDN
IN
V
4 SHDN
IN
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
= 125°C, θ = 250°C/ W, θ = 102°C/W
DCB PACKAGE
6-LEAD (2mm s 3mm) PLASTIC DFN
T
JMAX
JA
JC
θ
= 73.5°C/ W, θ = 12°C/W
JC
EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDEDED TO PCB
JA
ORDER INFORMATION
LEAD FREE FINISH
LT1934ES6#PBF
LT1934ES6-1#PBF
LT1934IS6#PBF
LT1934IS6-1#PBF
LT1934IDCB#PBF
LT1934EDCB#PBF
LT1934IDCB-1#PBF
LT1934EDCB-1#PBF
LEAD BASED FINISH
LT1934ES6
TAPE AND REEL
S6 PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT1934ES6#TRPBF
LT1934ES6-1#TRPBF
LT1934IS6#TRPBF
LT1934IS6-1#TRPBF
LT1934IDCB#TRPBF
LT1934EDCB#TRPBF
LT1934IDCB-1#TRPBF
LT1934EDCB-1#TRPBF
TAPE AND REEL
LTXP
6-Lead Plastic TSOT-23
–40°C to 85°C
–40°C to 85°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 85°C
–40°C to 125°C
–40°C to 85°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 85°C
–40°C to 125°C
–40°C to 85°C
LTF8
6-Lead Plastic TSOT-23
LTAJB
LTAJC
LCFZ
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead (2mm × 3mm) Plastic DFN
6-Lead (2mm × 3mm) Plastic DFN
6-Lead (2mm × 3mm) Plastic DFN
6-Lead (2mm × 3mm) Plastic DFN
PACKAGE DESCRIPTION
LCFZ
LDHC
LDHC
S6 PART MARKING*
LTXP
LT1934ES6#TR
6-Lead Plastic TSOT-23
LT1934ES6-1
LT1934ES6-1#TR
LT1934IS6#TR
LTF8
6-Lead Plastic TSOT-23
LT1934IS6
LTAJB
LTAJC
LCFZ
6-Lead Plastic TSOT-23
LT1934IS6-1
LT1934IS6-1#TR
6-Lead Plastic TSOT-23
LT1934IDCB
LT1934IDCB#TR
6-Lead (2mm × 3mm) Plastic DFN
6-Lead (2mm × 3mm) Plastic DFN
6-Lead (2mm × 3mm) Plastic DFN
6-Lead (2mm × 3mm) Plastic DFN
LT1934EDCB
LT1934EDCB#TR
LT1934IDCB-1#TR
LT1934EDCB-1#TR
LCFZ
LT1934IDCB-1
LDHC
LDHC
LT1934EDCB-1
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/
This product is only offered in trays. For more information go to: http://www.linear.com/packaging/
1934fe
2
LT1934/LT1934-1
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 10V, VBOOST = 15V, unless otherwise noted.
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Undervoltage Lockout
3
3
3
3.2
3.6
3.6
V
V
V
l
l
–40°C ≤ T ≤ 85°C
A
–40°C ≤ T ≤ 125°C
A
Quiescent Current
V
FB
= 1.3V
12
12
12
22
26
26
μA
μA
μA
l
l
–40°C ≤ T ≤ 85°C
A
–40°C ≤ T ≤ 125°C
A
V
V
= 0V
0.01
2
μA
SHDN
l
l
FB Comparator Trip Voltage
Falling
–40°C ≤ T ≤ 85°C
1.22
1.21
1.25
1.25
1.27
1.27
V
V
FB
A
–40°C ≤ T ≤ 125°C
A
FB Comparator Hysteresis
FB Pin Bias Current
10
mV
l
l
V
FB
= 1.25V
–40°C ≤ T ≤ 85°C
2
2
15
60
nA
nA
A
–40°C ≤ T ≤ 125°C
A
FB Voltage Line Regulation
Switch Off Time
4V < V < 34V
0.007
%/V
IN
V
FB
V
FB
> 1V
= 0V
1.4
1.8
12
2.3
μs
μs
l
l
Maximum Duty Cycle
V
FB
= 1V
–40°C ≤ T ≤ 85°C
85
83
88
88
%
%
A
–40°C ≤ T ≤ 125°C
A
Switch V
I
SW
I
SW
I
SW
I
SW
= 300mA (LT1934, S6 Package)
= 300mA (LT1934, DCB Package)
= 75mA (LT1934-1, S6 Package)
= 75mA (LT1934-1, DCB Package)
200
225
65
300
120
mV
mV
mV
mV
CESAT
70
Switch Current Limit
LT1934
LT1934-1
350
90
400
120
490
160
mA
mA
BOOST Pin Current
I
SW
I
SW
= 300mA (LT1934)
= 75mA (LT1934-1)
8.5
6.0
12
10
mA
mA
Minimum Boost Voltage (Note 3)
I
SW
I
SW
= 300mA (LT1934)
= 75mA (LT1934-1)
1.8
1.7
2.5
2.5
V
V
Switch Leakage Current
2
μA
SHDN Pin Current
V
SHDN
V
SHDN
= 2.3V
= 34V
0.5
1.5
μA
μA
5
SHDN Input Voltage High
SHDN Input Voltage Low
2.3
V
V
0.25
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.
operating temperature range are assured by design, characterization and
correlation with statistical process controls. The LT1934I and LT1934I-1
specifications are guaranteed over the –40°C to 125°C temperature range.
Note 3: This is the minimum voltage across the boost capacitor needed to
Note 2: The LT1934E and LT1934E-1 are guaranteed to meet performance
guarantee full saturation of the internal power switch.
specifications from 0°C to 85°C. Specifications over the –40°C to 85°C
1934fe
3
LT1934/LT1934-1
TYPICAL PERFORMANCE CHARACTERISTICS
LT1934 Efficiency, VOUT = 5V
LT1934 Efficiency, VOUT = 3.3V
LT1934-1 Efficiency, VOUT = 5V
100
90
80
70
60
50
100
90
80
70
60
50
100
90
80
70
60
50
LT1934
LT1934
LT1934-1
V
= 5V
V
= 3.3V
V
= 5V
OUT
OUT
OUT
L = 47μH
= 25°C
L = 47μH
T = 25°C
A
L = 150μH
= 25°C
T
T
A
A
V
= 5V
V
= 12V
IN
IN
V
V
= 12V
= 24V
IN
V
= 24V
IN
V
= 24V
IN
IN
V
= 12V
IN
0.1
1
10
100
0.1
1
10
100
0.1
1
10
100
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
1934 G01
1934 G02
1934 G03
LT1934-1 Efficiency, VOUT = 3.3V
Current Limit vs Temperature
Off Time vs Temperature
500
400
300
200
100
0
3.0
2.5
2.0
1.5
100
90
80
70
60
50
LT1934-1
LT1934
V
= 3.3V
OUT
L = 100μH
= 25°C
T
A
V
= 12V
IN
V
= 24V
IN
1.0
0.5
0
LT1934-1
50
TEMPERATURE (°C)
100 125
50
75 100 125
–50 –25
0
25
75
0.1
1
10
100
–50 –25
0
25
TEMPERATURE (°C)
LOAD CURRENT (mA)
1934 G06
1934 G04
1934 G05
SHDN Bias Current
vs SHDN Voltage
Frequency Foldback
VFB vs Temperature
1.27
1.26
1.25
1.24
1.23
1.22
2.0
1.5
1.0
0.5
16
14
12
10
T
= 25°C
T
= 25oC
A
A
8
6
4
2
0
0
0.2
0.4
0.8
–50 –25
0
25
50
75 100 125
0
2
4
6
8
10
12
0
1.0
1.2
0.6
SHDN PIN VOLTAGE (V)
TEMPERATURE (°C)
FEEDBACK PIN VOLTAGE (V)
1934 G07
1934 G08
1934 G09
1934fe
4
LT1934/LT1934-1
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current
vs Temperature
Undervoltage Lockout
vs Temperature
20
15
10
5
4.0
3.5
3.0
2.5
0
2.0
–50 –25
0
25
50
75 100 125
–50 –25
0
25
50
75 100 125
TEMPERATURE (°C)
TEMPERATURE (°C)
1934 G10
1934 G11
Minimum Input Voltage
VOUT = 3.3V
Minimum Input Voltage
VOUT = 5V
6.0
5.5
5.0
4.5
4.0
3.5
3.0
8
7
6
5
4
LT1934
LT1934
V
T
= 3.3V
V
T
= 5V
OUT
A
OUT
A
= 25°C
= 25°C
BOOST DIODE TIED TO OUTPUT
BOOST DIODE TIED TO OUTPUT
V
TO START
IN
V
TO START
IN
V
TO RUN
IN
V
TO RUN
IN
0.1
1
10
100
0.1
1
10
100
LOAD CURRENT (mA)
LOAD CURRENT (mA)
1934 G12
1934 G13
PIN FUNCTIONS (TSOT-23/DFN)
BOOST (Pin 1/Pin 1): The BOOST pin is used to provide a inshutdownmode.TietogroundtoshutdowntheLT1934.
drive voltage, higher than the input voltage, to the internal Apply 2.3V or more for normal operation. If the shutdown
bipolar NPN power switch.
feature is not used, tie this pin to the V pin.
IN
GND (Pin 2/Pin 5): Tie the GND pin to a local ground plane VIN (Pin 5/Pin 3): The V pin supplies current to the
IN
below the LT1934 and the circuit components. Return the LT1934’s internal regulator and to the internal power
feedback divider to this pin.
switch. This pin must be locally bypassed.
FB (Pin 3/Pin 6): The LT1934 regulates its feedback pin SW (Pin 6/Pin 2): The SW pin is the output of the internal
to 1.25V. Connect the feedback resistor divider tap to this powerswitch.Connectthispintotheinductor,catchdiode
pin. Set the output voltage according to V
= 1.25V and boost capacitor.
OUT
(1 + R1/R2) or R1 = R2 (V /1.25 – 1).
OUT
Exposed Pad (Pin 7, DFN Package): This pin must be
SHDN(Pin4/Pin4):TheSHDNpinisusedtoputtheLT1934 soldered to ground plane.
1934fe
5
LT1934/LT1934-1
BLOCK DIAGRAM
V
IN
V
IN
+
C2
+
–
D2
BOOST
SW
ON TIME
R
S
Qa
C3
D1
12μs DELAY
Q
L1
OFF TIME
V
OUT
1.8μs DELAY
C1
SHDN
ON OFF
V
1.25V
REF
+
–
ENABLE
FEEDBACK
COMPARATOR
GND
FB
R1
R2
1934 BD
1934fe
6
LT1934/LT1934-1
(Refer to Block Diagram)
OPERATION
The LT1934 uses Burst Mode control, combining both low
quiescentcurrentoperationandhighswitchingfrequency,
which result in high efficiency across a wide range of load
currents and a small total circuit size.
flip-flop when this current reaches 400mA (120mA for
the LT1934-1). After the 1.8μs delay of the off-time one-
shot, the cycle repeats. Generally, the LT1934 will reach
current limit on every cycle—the off time is fixed and
the on time is regulated so that the LT1934 operates at
the correct duty cycle. The 1.8μs off time is lengthened
when the FB pin voltage falls below 0.8V; this foldback
behavior helps control the output current during start-up
and overload. Figure 1 shows several waveforms of an
LT1934producing3.3Vfroma10Vinput.Whentheswitch
is on, the SW pin voltage is at 10V. When the switch is
off, the inductor current pulls the SW pin down until it is
clamped near ground by the external catch diode.
A comparator monitors the voltage at the FB pin of the
LT1934. If this voltage is higher than the internal 1.25V
reference,thecomparatordisablestheoscillatorandpower
switch. In this state, only the comparator, reference and
undervoltagelockoutcircuitsareactive,andthecurrentinto
the V pin is just 12μA. As the load current discharges the
IN
outputcapacitor,thevoltageattheFBpinfallsbelow1.25V
and the comparator enables the oscillator. The LT1934
begins to switch, delivering current to the output capaci-
tor. The output voltage rises, and when it overcomes the
feedbackcomparator’shysteresis,theoscillatorisdisabled
and the LT1934 returns to its micropower state.
The switch driver operates from either the input or from
the BOOST pin. An external capacitor and diode are used
to generate a voltage at the BOOST pin that is higher than
the input supply. This allows the driver to fully saturate
the bipolar switch for efficient operation.
The oscillator consists of two one-shots and a flip-flop.
Arisingedgefromtheoff-timeone-shotsetstheflip-flop,
whichturnsontheinternalNPNpowerswitch.Theswitch
remains on until either the on-time one-shot trips or the
current limit is reached. A sense resistor and amplifier
monitor the current through the switch and resets the
If the SHDN pin is grounded, all internal circuits are turned
off and V current reduces to the device leakage current,
IN
typically a few nA.
V
OUT
50mV/DIV
V
SW
10V/DIV
I
SW
0.5A/DIV
I
LI
0.5A/DIV
1934 F01a
5μs/DIV
Figure 1. Operating Waveforms of the LT1934 Converting
10V to 3.3V at 180mA (Front Page Schematic)
1934fe
7
LT1934/LT1934-1
APPLICATIONS INFORMATION
Which One to Use: LT1934 or LT1934-1?
The duty cycle is the fraction of time that the internal
switch is on and is determined by the input and output
voltages:
The only difference between the LT1934 and LT1934-1
is the peak current through the internal switch and the
inductor. Ifyourmaximumloadcurrentislessthan60mA,
use the LT1934-1. If your maximum load is higher, use
the LT1934; it can supply up to ~300mA.
DC = (V
+ V )/(V – V + V )
D IN SW D
OUT
where V is the forward voltage drop of the catch diode
D
(~0.4V) and V is the voltage drop of the internal switch
SW
While the LT1934-1 can’t deliver as much output current,
it has other advantages. The lower peak switch current
allows the use of smaller components (input capacitor,
inductor and output capacitor). The ripple current at the
input of the LT1934-1 circuit will be smaller and may be
an important consideration if the input supply is current
limited or has high impedance. The LT1934-1’s current
draw during faults (output overload or short) and start-
up is lower.
(~0.3V at maximum load for the LT1934, ~0.1V for the
LT1934-1). This leads to a minimum input voltage of:
V
= (V
+ V )/DC
– V + V
MAX D SW
IN(MIN)
OUT
D
with DC
= 0.85.
MAX
Inductor Selection
A good first choice for the inductor value is:
L = 2.5 • (V + V ) • 1.8μs/I
OUT
D
LIM
The maximum load current that the LT1934 or LT1934-1
can deliver depends on the value of the inductor used.
Table 1 lists inductor value, minimum output capacitor
and maximum load for 3.3V and 5V circuits. Increasing
the value of the capacitor will lower the output voltage
ripple. Component selection is covered in more detail in
the following sections.
where I
is the switch current limit (400mA for the
LIM
LT1934and120mAfortheLT1934-1).Thischoiceprovides
a worst-case maximum load current of 250mA (60mA for
the LT1934-1). The inductor’s RMS current rating must
be greater than the load current and its saturation current
should be greater than I . To keep efficiency high, the
LIM
series resistance (DCR) should be less than 0.3Ω (1Ω
for the LT1934-1). Table 2 lists several vendors and types
that are suitable.
Minimum Input Voltage
The minimum input voltage required to generate a par-
ticular output voltage is determined by either the LT1934’s
undervoltagelockoutof~3Vorbyitsmaximumdutycycle.
This simple rule may not provide the optimum value for
your application. If the load current is less, then you can
relax the value of the inductor and operate with higher
ripple current. This allows you to use a physically smaller
inductor, or one with a lower DCR resulting in higher
efficiency. The following provides more details to guide
inductor selection. First, the value must be chosen so that
the LT1934 can supply the maximum load current drawn
from the output. Second, the inductor must be rated ap-
propriately so that the LT1934 will function reliably and
the inductor itself will not be overly stressed.
Table 1
MINIMUM
MAXIMUM
LOAD
PART
V
L
C
OUT
OUT
LT1934
3.3V
100μH
47μH
33μH
100μH
47μH
33μH
300mA
250mA
200mA
5V
150μH
68μH
47μH
47μH
33μH
22μH
300mA
250mA
200mA
LT1934-1
3.3V
5V
150μH
100μH
68μH
15μH
10μH
10μH
60mA
45mA
20mA
Detailed Inductor Selection and
Maximum Load Current
220μH
150μH
100μH
10μH
4.7μH
4.7μH
60mA
45mA
20mA
The square wave that the LT1934 produces at its switch
pinresultsinatrianglewaveofcurrentintheinductor. The
LT1934 limits the peak inductor current to I . Because
LIM
1934fe
8
LT1934/LT1934-1
APPLICATIONS INFORMATION
Table 2. Inductor Vendors
VENDOR
Murata
PHONE
URL
PART SERIES
COMMENTS
Small, Low Cost, 2mm Height
(404) 426-1300
(847) 956-0666
www.murata.com
www.sumida.com
LQH3C
Sumida
CR43
CDRH4D28
CDRH5D28
Coilcraft
(847) 639-6400
(866) 362-6673
www.coilcraft.com
www.we-online.com
DO1607C
DO1608C
DT1608C
Würth
WE-PD1, 2, 3, 4
Electronics
the average inductor current equals the load current, the
maximum load current is:
The inductor must carry the peak current without satu-
rating excessively. When an inductor carries too much
current, its core material can no longer generate ad-
ditional magnetic flux (it saturates) and the inductance
drops, sometimes very rapidly with increasing current.
This condition allows the inductor current to increase
at a very high rate, leading to high ripple current and
decreased overload protection.
I
= I – ΔI /2
PK L
OUT(MAX)
where I is the peak inductor current and ΔI is the
PK
L
peak-to-peak ripple current in the inductor. The ripple
current is determined by the off time, t
the inductor value:
= 1.8μs, and
OFF
ΔI = (V
+ V ) • t /L
D OFF
Inductorvendorsprovidecurrentratingsforpowerinduc-
tors. These are based on either the saturation current or
on the RMS current that the inductor can carry without
dissipating too much power. In some cases it is not clear
whichofthesetwodeterminethecurrentrating.Somedata
sheets are more thorough and show two current ratings,
one for saturation and one for dissipation. For LT1934 ap-
plications, the RMS current rating should be higher than
the load current, while the saturation current should be
higher than the peak inductor current calculated above.
L
OUT
I
is nominally equal to I . However, there is a slight
LIM
PK
delay in the control circuitry that results in a higher peak
current and a more accurate value is:
I
= I + 150ns • (V – V )/L
LIM IN OUT
PK
These expressions are combined to give the maximum
load current that the LT1934 will deliver:
I
= 350mA + 150ns • (V – V )/L – 1.8μs
IN OUT
OUT(MAX)
• (V
+ V )/2L (LT1934)
OUT
D
Input Capacitor
I
= 90mA + 150ns • (V – V )/L – 1.8μs
IN OUT
D
OUT(MAX)
• (V
+ V )/2L (LT1934-1)
OUT
Step-down regulators draw current from the input sup-
ply in pulses with very fast rise and fall times. The input
capacitor is required to reduce the resulting voltage ripple
at the LT1934 and to force this switching current into
a tight local loop, minimizing EMI. The input capacitor
must have low impedance at the switching frequency to
do this effectively. A 2.2μF ceramic capacitor (1μF for the
LT1934-1) satisfies these requirements.
Theminimumcurrentlimitisusedheretobeconservative.
The third term is generally larger than the second term,
so that increasing the inductor value results in a higher
output current. This equation can be used to evaluate
a chosen inductor or it can be used to choose L for a
givenmaximumloadcurrent.Thesimple,singleequation
rule given above for choosing L was found by setting
ΔI =I /2.5.ThisresultsinI
~0.8I (ignoring
L
LIM
OUT(MAX)
LIM
If the input source impedance is high, a larger value ca-
pacitor may be required to keep input ripple low. In this
case, an electrolytic of 10μF or more in parallel with a 1μF
the delay term). Note that this analysis assumes that the
inductor current is continuous, which is true if the ripple
current is less than the peak current or ΔI < I .
L
PK
ceramic is a good combination. Be aware that the input
1934fe
9
LT1934/LT1934-1
APPLICATIONS INFORMATION
capacitor is subject to large surge currents if the LT1934
circuit is connected to a low impedance supply, and that
some electrolytic capacitors (in particular tantalum) must
be specified for such use.
The LT1934-1, with its lower switch current, can use a
B-case tantalum capacitor.
With a high quality capacitor filtering the ripple current
from the inductor, the output voltage ripple is determined
by the hysteresis and delay in the LT1934’s feedback
comparator. This ripple can be reduced further by adding
a small (typically 10pF) phase lead capacitor between the
output and the feedback pin.
Output Capacitor and Output Ripple
Theoutputcapacitorfilterstheinductor’sripplecurrentand
stores energy to satisfy the load current when the LT1934
is quiescent. In order to keep output voltage ripple low, the
impedance of the capacitor must be low at the LT1934’s
switching frequency. The capacitor’s equivalent series
resistance (ESR) determines this impedance. Choose one
with low ESR intended for use in switching regulators. The
contribution to ripple voltage due to the ESR is approxi-
Ceramic Capacitors
Ceramic capacitors are small, robust and have very low
ESR. However, ceramic capacitors can cause problems
when used with the LT1934.
Not all ceramic capacitors are suitable. X5R and X7R
types are stable over temperature and applied voltage
and give dependable service. Other types (Y5V and Z5U)
have very large temperature and voltage coefficients of
capacitance. In the application circuit they may have only
a small fraction of their nominal capacitance and voltage
ripple may be much larger than expected.
mately I • ESR. ESR should be less than ~150mΩ for
LIM
the LT1934 and less than ~500mΩ for the LT1934-1.
The value of the output capacitor must be large enough
to accept the energy stored in the inductor without a large
changeinoutputvoltage. Settingthisvoltagestepequalto
1% of the output voltage, the output capacitor must be:
2
C
OUT
> 50 • L • (I /V
)
LIM OUT
Ceramiccapacitorsarepiezoelectric.TheLT1934’sswitch-
ing frequency depends on the load current, and at light
loads the LT1934 can excite the ceramic capacitor at audio
frequencies, generating audible noise. If this is unaccept-
able, use a high performance electrolytic capacitor at the
output. The input capacitor can be a parallel combination
of a 2.2μF ceramic capacitor and a low cost electrolytic
capacitor. The level of noise produced by the LT1934-1
For example, an LT1934 producing 3.3V with L = 47μH
requires 33μF. This value can be relaxed if small circuit
size is more important than low output ripple.
Sanyo’s POSCAP series in B-case and C-case sizes
provides very good performance in a small package for
the LT1934. Similar performance in traditional tantalum
capacitors requires a larger package (C- or D-case).
Table 3. Capacitor Vendors
VENDOR
PHONE
URL
PART SERIES
COMMENTS
Panasonic
(714) 373-7366
www.panasonic.com
Ceramic,
Polymer,
Tantalum
EEF Series
Kemet
Sanyo
(864) 963-6300
(408) 749-9714
www.kemet.com
Ceramic,
Tantalum
T494, T495
POSCAP
www.sanyovideo.com Ceramic,
Polymer,
Tantalum
Murata
AVX
(404) 436-1300
www.murata.com
www.avxcorp.com
Ceramic,
Ceramic,
Tantalum
TPS Series
Taiyo Yuden (864) 963-6300
www.taiyo-yuden.com Ceramic
1934fe
10
LT1934/LT1934-1
APPLICATIONS INFORMATION
when used with ceramic capacitors will be lower and may
be acceptable.
D2
BOOST
LT1934
C3
A final precaution regarding ceramic capacitors concerns
themaximuminputvoltageratingoftheLT1934.Aceramic
input capacitor combined with trace or cable inductance
forms a high quality (under damped) tank circuit. If the
LT1934 circuit is plugged into a live supply, the input volt-
agecanringtotwiceitsnominalvalue,possiblyexceeding
the LT1934’s rating. This situation is easily avoided; see
the Hot Plugging Safely section.
V
IN
V
OUT
V
SW
IN
GND
V
– V V
SW OUT
BOOST
MAX V
V + V
IN OUT
BOOST
(2a)
D2
C3
BOOST
LT1934
Catch Diode
V
IN
V
OUT
V
SW
IN
A 0.5A Schottky diode is recommended for the catch
diode, D1. The diode must have a reverse voltage rating
equal to or greater than the maximum input voltage. The
ON Semiconductor MBR0540 is a good choice; it is rated
for 0.5A forward current and a maximum reverse voltage
of 40V.
GND
1934 F02
V
– V V
BOOST
SW
IN
IN
MAX V
2V
BOOST
(2b)
Figure 2. Two Circuits for Generating the Boost Voltage
Schottky diodes with lower reverse voltage ratings usu-
ally have a lower forward drop and may result in higher
efficiency with moderate to high load currents. However,
thesediodesalsohavehigherleakagecurrents.Thisleakage
current mimics a load current at the output and can raise
the quiescent current of the LT1934 circuit, especially at
elevated temperatures.
the maximum duty cycle as outlined above. For proper
start-up, the minimum input voltage is also limited by the
boost circuit. If the input voltage is ramped slowly, or the
LT1934 is turned on with its SHDN pin when the output
is already in regulation, then the boost capacitor may not
be fully charged. Because the boost capacitor is charged
with the energy stored in the inductor, the circuit will rely
on some minimum load current to get the boost circuit
running properly. This minimum load will depend on input
and output voltages, and on the arrangement of the boost
circuit. The minimum load generally goes to zero once the
circuit has started. Figure 3 shows a plot of minimum load
to start and to run as a function of input voltage. In many
cases the discharged output capacitor will present a load
to the switcher which will allow it to start. The plots show
BOOST Pin Considerations
Capacitor C3 and diode D2 are used to generate a boost
voltagethatishigherthantheinputvoltage. Inmostcases
a 0.1μF capacitor and fast switching diode (such as the
1N4148 or 1N914) will work well. Figure 2 shows two
ways to arrange the boost circuit. The BOOST pin must
be more than 2.5V above the SW pin for best efficiency.
For outputs of 3.3V and above, the standard circuit (Fig-
ure 2a) is best. For outputs between 2.8V and 3V, use a
0.22μF capacitor and a small Schottky diode (such as the
BAT-54). For lower output voltages the boost diode can be
tiedtotheinput(Figure2b). ThecircuitinFigure2aismore
efficientbecausetheBOOSTpincurrentcomesfromalower
voltage source. You must also be sure that the maximum
voltage rating of the BOOST pin is not exceeded.
theworst-casesituationwhereV isrampingveryslowly.
IN
Use a Schottky diode (such as the BAT-54) for the lowest
start-up voltage.
At light loads, the inductor current becomes discontinu-
ous and the effective duty cycle can be very high. This
reduces the minimum input voltage to approximately
300mV above V . At higher load currents, the inductor
OUT
The minimum operating voltage of an LT1934 applica-
tion is limited by the undervoltage lockout (~3V) and by
current is continuous and the duty cycle is limited by the
1934fe
11
LT1934/LT1934-1
APPLICATIONS INFORMATION
Minimum Input Voltage VOUT = 3.3V
to V ), then the LT1934’s internal circuitry will pull its
IN
6.0
quiescent current through its SW pin. This is fine if your
system can tolerate a few mA in this state. If you ground
the SHDN pin, the SW pin current will drop to essentially
LT1934
OUT
T = 25°C
A
V
= 3.3V
5.5
5.0
4.5
4.0
3.5
3.0
BOOST DIODE TIED TO OUTPUT
TO START
zero. However, if the V pin is grounded while the output
IN
V
IN
is held high, then parasitic diodes inside the LT1934 can
pull large currents from the output through the SW pin
and the V pin. Figure 4 shows a circuit that will run only
IN
V
IN
TO RUN
whentheinputvoltageispresentandthatprotectsagainst
a shorted or reversed input.
D4
0.1
1
10
100
5
4
1
6
V
IN
V
BOOST
SW
IN
LOAD CURRENT (mA)
1934 G12
LT1934
100k
1M
V
OUT
SHDN
Minimum Input Voltage VOUT = 5V
GND
2
FB
3
8
7
6
5
4
LT1934
V
= 5V
OUT
A
BACKUP
T
= 25°C
BOOST DIODE TIED TO OUTPUT
V
TO START
D4: MBR0530
IN
1934 F07
Figure 4. Diode D4 Prevents a Shorted Input from Discharging
a Backup Battery Tied to the Output; It Also Protects the Circuit
from a Reversed Input. The LT1934 Runs Only When the Input
is Present
V
IN
TO RUN
PCB Layout
0.1
1
10
100
LOAD CURRENT (mA)
For proper operation and minimum EMI, care must be
taken during printed circuit board layout. Figure 5 shows
the high current paths in the buck regulator circuit. Note
that large, switched currents flow in the power switch,
the catch diode (D1) and the input capacitor (C2). The
loop formed by these components should be as small as
possible. Furthermore, the system ground should be tied
to the regulator ground in only one place; this prevents
the switched current from injecting noise into the system
ground. These components, along with the inductor and
output capacitor, should be placed on the same side of
the circuit board, and their connections should be made
on that layer. Place a local, unbroken ground plane below
these components, and tie this ground plane to system
ground at one location, ideally at the ground terminal of
the output capacitor C1. Additionally, the SW and BOOST
nodes should be kept as small as possible. Finally, keep
the FB node as small as possible so that the ground pin
1934 G13
Figure 3. The Minimum Input Voltage Depends
on Output Voltage, Load Current and Boost Circuit
maximum duty cycle of the LT1934, requiring a higher
input voltage to maintain regulation.
Shorted Input Protection
If the inductor is chosen so that it won’t saturate exces-
sively, an LT1934 buck regulator will tolerate a shorted
output. There is another situation to consider in systems
where the output will be held high when the input to the
LT1934 is absent. This may occur in battery charging ap-
plications or in battery backup systems where a battery
or some other supply is diode OR-ed with the LT1934’s
output. If the V pin is allowed to float and the SHDN pin
is held high (either by a logic signal or because it is tied
IN
1934fe
12
LT1934/LT1934-1
APPLICATIONS INFORMATION
V
IN
SW
V
SW
IN
GND
GND
(5a)
(5b)
I
C1
V
SW
L1
V
IN
SW
C2
D1
C1
GND
1934 F05
(5c)
Figure 5. Subtracting the Current When the Switch is On (a) from the Current When the Switch is Off (b) Reveals the Path of the High
Frequency Switching Current (c). Keep This Loop Small. The Voltage on the SW and BOOST Nodes Will Also be Switched; Keep These
Nodes as Small as Possible. Finally, Make Sure the Circuit is Shielded with a Local Ground Plane
SHUTDOWN
V
IN
V
OUT
SYSTEM
GROUND
1934 F06
VIAS TO LOCAL GROUND PLANE
OUTLINE OF LOCAL GROUND PLANE
Figure 6. A Good PCB Layout Ensures Proper, Low EMI Operation
and ground traces will shield it from the SW and BOOST
is plugged into a live supply (see Linear Technology
Application Note 88 for a complete discussion). The low
loss ceramic capacitor combined with stray inductance in
series with the power source forms an under damped tank
nodes. Figure 6 shows component placement with trace,
ground plane and via locations. Include two vias near
the GND pin of the LT1934 to help remove heat from the
LT1934 to the ground plane.
circuit, and the voltage at the V pin of the LT1934 can
IN
ringtotwicethenominalinputvoltage,possiblyexceeding
the LT1934’s rating and damaging the part. If the input
supply is poorly controlled or the user will be plugging
the LT1934 into an energized supply, the input network
should be designed to prevent this overshoot.
Hot Plugging Safely
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypass capacitor of LT1934 and LT1934-1 circuits. How-
ever, these capacitors can cause problems if the LT1934
1934fe
13
LT1934/LT1934-1
APPLICATIONS INFORMATION
Figure 7 shows the waveforms that result when an LT1934 an aluminum electrolytic capacitor has been added. This
circuit is connected to a 24V supply through six feet of capacitor’s high equivalent series resistance damps the
24-gauge twisted pair. The first plot is the response with circuit and eliminates the voltage overshoot. The extra
a 2.2μF ceramic capacitor at the input. The input voltage capacitor improves low frequency ripple filtering and can
rings as high as 35V and the input current peaks at 20A. slightly improve the efficiency of the circuit, though it is
One method of damping the tank circuit is to add another likelytobethelargestcomponentinthecircuit. Analterna-
capacitor with a series resistor to the circuit. In Figure 7b tive solution is shown in Figure 7c. A 1Ω resistor is added
CLOSING SWITCH
SIMULATES HOT PLUG
I
IN
V
IN
LT1934
2.2μF
V
IN
10V/DIV
+
I
IN
10A/DIV
LOW
STRAY
IMPEDANCE
ENERGIZED
24V SUPPLY
INDUCTANCE
DUE TO 6 FEET
(2 METERS) OF
TWISTED PAIR
10μs/DIV
(7a)
LT1934
2.2μF
+
10μF
35V
AI.EI.
(7b)
1Ω
LT1934
2.2μF
0.1μF
(7c)
(7d)
LT1934-1
1μF
4.7Ω
LT1934-1
1μF
0.1μF
1934 F07
(7e)
Figure 7. A Well Chosen Input Network Prevents Input Voltage Overshoot and
Ensures Reliable Operation When the LT1934 is Connected to a Live Supply
1934fe
14
LT1934/LT1934-1
APPLICATIONS INFORMATION
in series with the input to eliminate the voltage overshoot
(it also reduces the peak input current). A 0.1μF capacitor
improves high frequency filtering. This solution is smaller
andlessexpensivethantheelectrolyticcapacitor. Forhigh
input voltages its impact on efficiency is minor, reducing
efficiency less than one half percent for a 5V output at full
load operating from 24V.
estimated by calculating the total power loss from an
efficiency measurement and subtracting the catch diode
loss. The resulting temperature rise at full load is nearly
independentofinputvoltage. Thermalresistancedepends
on the layout of the circuit board, but a value of 150°C/W
is typical for the TSOT-23 and 75°C/W for the DFN.
The temperature rise for an LT1934 (TSOT-23) producing
5V at 250mA is approximately 25°C, allowing it to deliver
full load to 100°C ambient. Above this temperature the
load current should be reduced. For 3.3V at 250mA the
temperature rise is 15°C. The DFN temperature rise will
be roughly one-half of these values.
Voltage overshoot gets worse with reduced input capaci-
tance. Figure 7d shows the hot plug response with a 1μF
ceramic input capacitor, with the input ringing above 40V.
The LT1934-1 can tolerate a larger input resistance, such
as shown in Figure 7e where a 4.7Ω resistor damps the
voltage transient and greatly reduces the input current
glitch on the 24V supply.
Finally, be aware that at high ambient temperatures the
external Schottky diode, D1, is likely to have significant
leakage current, increasing the quiescent current of the
LT1934 converter.
High Temperature Considerations
The die temperature of the LT1934 must be lower than the
maximum rating of 125°C. This is generally not a concern
unless the ambient temperature is above 85°C. For higher
temperatures, care should be taken in the layout of the
circuit to ensure good heat sinking of the LT1934. The
maximum load current should be derated as the ambient
temperature approaches 125°C.
Outputs Greater Than 6V
Foroutputsgreaterthan6V, tieadiode(suchasa1N4148)
from the SW pin to V to prevent the SW pin from ringing
IN
above V during discontinuous mode operation. The 12V
IN
outputcircuitinTypicalApplicationsshowsthelocationof
this diode. Also note that for outputs above 6V, the input
voltage range will be limited by the maximum rating of
the BOOST pin. The 12V circuit shows how to overcome
this limitation using an additional Zener diode.
ThedietemperatureiscalculatedbymultiplyingtheLT1934
power dissipation by the thermal resistance from junction
to ambient. Power dissipation within the LT1934 can be
1934fe
15
LT1934/LT1934-1
TYPICAL APPLICATIONS
3.3V Step-Down Converter
D2
0.1μF
L1
100μH
BOOST
V
OUT
V
IN
V
SW
FB
3.3V
IN
4.5V TO 34V
45mA
C2
1μF
D1
LT1934-1
10pF
1M
+
C1
22μF
ON OFF
SHDN
GND
604k
C1: TAIYO YUDEN JMK316BJ226ML
C2: TAIYO YUDEN GMK316BJ105ML
1934 TA04
D1: ZETEX ZHCS400 OR ON SEMI MBR0540
D2: CENTRAL CMDSH-3
L1: COILCRAFT DO1608C-104 OR
WURTH ELECTRONICS WE-PD4 TYPE S
5V Step-Down Converter
D2
0.1μF
L1
150μH
BOOST
V
OUT
V
IN
V
SW
FB
5V
IN
6.5V TO 34V
45mA
C2
1μF
D1
LT1934-1
10pF
1M
+
C1
22μF
ON OFF
SHDN
GND
332k
C1: TAIYO YUDEN JMK316BJ226ML
C2: TAIYO YUDEN GMK316BJ105ML
1934 TA05
D1: ZETEX ZHCS400 OR ON SEMI MBR0540
D2: CENTRAL CMPD914
L1: COILCRAFT DO1608C-154 OR
WURTH ELECTRONICS WE-PD4 TYPE S
1934fe
16
LT1934/LT1934-1
TYPICAL APPLICATIONS
1.8V Step-Down Converter
D2
0.1μF
L1
BOOST
LT1934
33μH
V
OUT
V
IN
V
SW
FB
1.8V
IN
3.6V TO 16V
250mA
C2
2.2μF
D1
147k
332k
+
C1
100μF
ON OFF
SHDN
GND
C1: SANYO 2R5TPB100M
1934 TA06
C2: TAIYO YUDEN EMK316BJ225ML
D1: ZETEX ZHCS400 OR ON SEMI MBR0540
D2: CENTRAL CMPD914
L1: SUMIDA CR43-330
Loop Powered 3.3V Supply with Additional Isolated Output
ISOLATED
OUT
D3
3V
+
3mA
L1B
50μH
10μF
•
D2
C1
L1A
50μH
BOOST
V
V
OUT
IN
V
SW
3V
14V TO 32V
<3.6mA
•
IN
9mA
10pF
1M
D1
LT1934-1
D4
10V
+
1μF
SHDN
GND
FB
33μF
390k
715k
D1: ON SEMICONDUCTOR MBR0540
D2, D3: BAT54
1934 TA08
D4: CENTRAL CMPZ5240B
L1: COILTRONICS CTX50-1
ZENER DIODE D4 PROVIDES AN UNDERVOLTAGE LOCKOUT,
REDUCING THE INPUT CURRENT REQUIRED AT START-UP
1934fe
17
LT1934/LT1934-1
TYPICAL APPLICATIONS
Standalone 350mA Li-Ion Battery Charger
D2
0.1μF
L1
47μH
1k
10k
0.047μF
BOOST
D3
1k
V
IN
V
IN
7V TO 28V
V
SW
FB
IN
CHRG
GATE
0.022μF
1M
D1
LT1934
LTC4052
ACPR SENSE
BAT
C2
1μF
SHDN
GND
+
C1
47μF
350mA
332k
TIMER GND
1-CELL 4.2V
Li-Ion
BATTERY
+
C
C5
10μF
TIMER
0.1μF
1934 TA07a
C1: SANYO 6TPB47M
C2: TAIYO YUDEN GMK316BJ105ML
(619) 661-6835
(408) 573-4150
CHARGE STATUS
AC PRESENT
D1, D3: ON SEMICONDUCTOR MBR0540 (602) 244-6600
D2: CENTRAL CMDSH-3
L1: SUMIDA CR43-470
(516) 435-1110
(847) 956-0667
500
400
300
200
100
0
V
V
= 24V
IN
V
= 8V
IN
= 12V
IN
2.5
3
3.5
4
4.5
BATTERY VOLTAGE (V)
1934 TA07b
12V Step-Down Converter
D2
0.1μF
D4
D3
L1
100μH
BOOST
V
OUT
V
IN
V
SW
FB
12V
IN
15V TO 32V
170mA
C2
2.2μF
LT1934
D1
866k
100k
+
C1
22μF
ON OFF
SHDN
GND
C1: KEMET T495D226K020AS
1934 TA09
C2: TAIYO YUDEN GMK325BJ225MN
D1: ON SEMI MBR0540
D2, D4: CENTRAL CMPD914
D3: CENTRAL CMPZ5234B 6.2V ZENER
L1: TDK SLF6028T-101MR42
1934fe
18
LT1934/LT1934-1
PACKAGE DESCRIPTION
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
2.90 BSC
(NOTE 4)
0.62
MAX
0.95
REF
1.22 REF
1.50 – 1.75
(NOTE 4)
2.80 BSC
1.4 MIN
3.85 MAX 2.62 REF
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.30 – 0.45
6 PLCS (NOTE 3)
0.95 BSC
0.80 – 0.90
0.20 BSC
DATUM ‘A’
0.01 – 0.10
1.00 MAX
0.30 – 0.50 REF
1.90 BSC
0.09 – 0.20
(NOTE 3)
S6 TSOT-23 0302 REV B
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
DCB Package
6-Lead Plastic DFN (2mm × 3mm)
(Reference LTC DWG # 05-08-1715)
R = 0.115
TYP
2.00 0.10
(2 SIDES)
0.40 0.10
R = 0.05
TYP
4
6
0.70 0.05
1.65 0.05
(2 SIDES)
3.00 0.10 1.65 0.10
(2 SIDES)
(2 SIDES)
3.55 0.05
2.15 0.05
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
PIN 1 NOTCH
R0.20 OR 0.25
s 45° CHAMFER
(DCB6) DFN 0405
PACKAGE
OUTLINE
3
1
0.25 0.05
0.25 0.05
0.50 BSC
0.50 BSC
0.75 0.05
0.200 REF
1.35 0.10
(2 SIDES)
1.35 0.05
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
0.00 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (TBD)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
1934fe
19
LT1934/LT1934-1
TYPICAL APPLICATION
5V Step-Down Converter
D2
0.1μF
L1
68μH
BOOST
V
OUT
V
IN
V
SW
FB
5V
IN
6.5V TO 34V
250mA
C2
2.2μF
D1
LT1934
10pF
1M
+
C1
68μF
ON OFF
SHDN
GND
332k
C1: SANYO 6TPB68M
C2: TAIYO YUDEN GMK325BJ225MN
1934 TA03
D1: ZETEX ZHCS400 OR ON SEMI MBR0540
D2: CENTRAL CMPD914
L1: SUMIDA CDRH5D28-680
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1616
25V, 500mA (I ), 1.4MHz, High Efficiency
Step-Down DC/DC Converter
V
= 3.6V to 25V, V
= 1.25V, I = 1.9mA, I < 1μA,
Q SD
OUT
IN
OUT
ThinSOT Package
LT1676
LT1765
LT1766
LT1767
LT1776
LTC®1877
LTC1879
LT1956
60V, 440mA (I ), 100kHz, High Efficiency
Step-Down DC/DC Converter
V
= 7.4V to 60V, V
= 1.24V, I = 3.2mA, I = 2.5μA,
Q SD
OUT
IN
OUT
S8 Package
25V, 2.75A (I ), 1.25MHz, High Efficiency
V
= 3V to 25V, V = 1.2V, I = 1mA, I = 15μA,
OUT Q SD
OUT
IN
Step-Down DC/DC Converter
S8, TSSOP16E Packages
V = 5.5V to 60V, V = 1.2V, I = 2.5mA, I = 25μA,
IN
60V, 1.2A (I ), 200kHz, High Efficiency
OUT
OUT
Q
SD
Step-Down DC/DC Converter
TSSOP16/E Package
= 3V to 25V; V = 1.2V, I = 1mA, I = 6μA,
OUT Q SD
25V, 1.2A (I ), 1.25MHz, High Efficiency
V
OUT
IN
Step-Down DC/DC Converter
MS8/E Packages
40V, 550mA (I ), 200kHz, High Efficiency
V
= 7.4V to 40V; V
= 1.24V, I = 3.2mA, I = 30μA,
OUT Q SD
OUT
IN
Step-Down DC/DC Converter
N8, S8 Packages
600mA (I ), 550kHz, Synchronous
V
= 2.7V to 10V; V
= 0.8V, I = 10μA, I < 1μA,
Q SD
OUT
IN
OUT
OUT
OUT
Step-Down DC/DC Converter
MS8 Package
1.2A (I ), 550kHz, Synchronous
V
= 2.7V to 10V; V
= 0.8V, I = 15μA, I < 1μA,
Q SD
OUT
IN
Step-Down DC/DC Converter
TSSOP16 Package
60V, 1.2A (I ), 500kHz, High Efficiency
V
= 5.5V to 60V, V
= 1.2V, I = 2.5mA, I = 25μA,
Q SD
OUT
IN
Step-Down DC/DC Converter
TSSOP16/E Package
= 2.7V to 6V, V = 0.8V, I = 20μA, I < 1μA,
OUT Q SD
LTC3405/LTC3405A 300mA (I ), 1.5MHz, Synchronous
V
OUT
IN
Step-Down DC/DC Converter
ThinSOT Package
LTC3406/LTC3406B 600mA (I ), 1.5MHz, Synchronous
V
= 2.5V to 5.5V, V
= 0.6V, I = 20μA, I < 1μA,
OUT Q SD
OUT
IN
Step-Down DC/DC Converter
ThinSOT Package
LTC3411
LTC3412
LTC3430
1.25A (I ), 4MHz, Synchronous
Step-Down DC/DC Converter
V
= 2.5V to 5.5V, V
= 0.8V, I = 60μA, I < 1μA,
Q SD
OUT
IN
OUT
OUT
OUT
MS Package
2.5A (I ), 4MHz, Synchronous
V
= 2.5V to 5.5V, V
= 0.8V, I = 60μA, I < 1μA,
Q SD
OUT
IN
Step-Down DC/DC Converter
TSSOP16E Package
60V, 2.75A (I ), 200kHz, High Efficiency
V
= 5.5V to 60V, V
= 1.2V, I = 2.5mA, I = 30μA,
Q SD
OUT
IN
Step-Down DC/DC Converter
TSSOP16E Package
1934fe
LT 0209 REV E • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
20
●
●
© LINEAR TECHNOLOGY CORPORATION 2002
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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