LT1934EDCB#TR [Linear]
IC 0.49 A SWITCHING REGULATOR, PDSO6, 2 X 3 MM, 0.80 MM HEIGHT, PLASTIC, MO-229, DFN-6, Switching Regulator or Controller;
| 型号： | LT1934EDCB#TR |
| 厂家： | 
Linear |
| 描述： | IC 0.49 A SWITCHING REGULATOR, PDSO6, 2 X 3 MM, 0.80 MM HEIGHT, PLASTIC, MO-229, DFN-6, Switching Regulator or Controller 稳压器 开关 |
| 文件： | 总20页 (文件大小：351K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1934/LT1934-1
Micropower Step-Down
Switching Regulators
in ThinSOT
U
FEATURES
DESCRIPTIO
■
Wide Input Voltage Range: 3.2V to 34V
The LT®1934 is a micropower step-down DC/DC con-
verter 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 bat-
teries. Quiescent current is just 12µA and a zero current
shutdown mode disconnects the load from the input
source, simplifying power management in battery-pow-
ered systems. Burst Mode® operation and the low drop
internalpowerswitchresultinhighefficiencyoverabroad
range of load current.
■
Micropower Operation: IQ = 12µA
■
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 VCESAT Switch: 200mV at 300mA
Low Profile (1mm) SOT-23 (ThinSOTTM) Package
■
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APPLICATIO S
■
Wall Transformer Regulation
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.
■
Automotive Battery Regulation
■
Standby Power for Portable Products
Distributed Supply Regulation
Industrial Control Supplies
■
■
, LTC and LT 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.
U
TYPICAL APPLICATIO
3.3V Step-Down Converter
Efficiency
100
D2
LT1934
IN
V
= 12V
90
80
70
60
50
0.22µF
L1
47µH
BOOST
LT1934
V
= 5V
OUT
V
OUT
V
IN
V
IN
SW
FB
3.3V
4.5V TO 34V
250mA
C2
V
= 3.3V
D1
OUT
2.2µF
10pF
1M
+
C1
100µF
ON OFF
SHDN
GND
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
1934f
1
LT1934/LT1934-1
W W
U W
U W
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ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1)
Input Voltage (VIN) ................................................. 34V
BOOST Pin Voltage ................................................. 40V
BOOST Pin Above SW Pin ...................................... 20V
SHDN Pin ............................................................... 34V
FB Voltage ................................................................ 6V
SW Voltage ............................................................... VIN
Operating Temperature Range (Note 2) ..........................
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).................. 300°C
ORDER PART
NUMBER
LT1934ES6
TOP VIEW
LT1934ES6-1
BOOST 1
GND 2
FB 3
6 SW
5 V
LT1934IS6
IN
LT1934IS6-1
4 SHDN
S6 PACKAGE
6-LEAD PLASTIC SOT-23
S6 PART MARKING
TJMAX = 125°C, θJA = 250°C/ W, θJC = 102°C/ W
LTXP
LTF8
LTAJB
LTAJC
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 10V, VBOOST = 15V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Undervoltage Lockout
3
3
3
3.2
3.6
3.6
V
V
V
–40°C ≤ T ≤ 85°C
●
●
A
–40°C ≤ T ≤ 125°C
A
Quiescent Current
V
= 1.3V
12
12
12
22
26
26
µA
µA
µA
FB
–40°C ≤ T ≤ 85°C
●
●
A
–40°C ≤ T ≤ 125°C
A
V
V
= 0V
0.01
2
µA
SHDN
FB Comparator Trip Voltage
Falling
–40°C ≤ T ≤ 85°C
●
●
1.22
1.21
1.25
1.25
1.27
1.27
V
V
A
FB
–40°C ≤ T ≤ 125°C
A
FB Comparator Hysteresis
FB Pin Bias Current
10
mV
V
= 1.25V
–40°C ≤ T ≤ 85°C
●
●
2
2
±15
±60
nA
nA
FB
A
–40°C ≤ T ≤ 125°C
A
FB Voltage Line Regulation
Switch Off Time
4V < V < 34V
0.007
%/V
IN
V
V
> 1V
= 0V
1.4
1.8
12
2.3
µs
µs
FB
FB
Maximum Duty Cycle
V
= 1V
–40°C ≤ T ≤ 85°C
●
●
85
83
88
88
%
%
A
FB
–40°C ≤ T ≤ 125°C
A
Switch V
I
I
= 300mA (LT1934)
= 75mA (LT1934-1)
200
65
300
120
mV
mV
CESAT
SW
SW
Switch Current Limit
LT1934
LT1934-1
350
90
400
120
490
160
mA
mA
BOOST Pin Current
I
I
= 300mA (LT1934)
= 75mA (LT1934-1)
8.5
6.0
12
10
mA
mA
SW
SW
Minimum Boost Voltage (Note 3)
Switch Leakage Current
I
I
= 300mA (LT1934)
= 75mA (LT1934-1)
1.8
1.7
2.5
2.5
V
V
SW
SW
2
µA
1934f
2
LT1934/LT1934-1
ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 10V, VBOOST = 15V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SHDN Pin Current
V
V
= 2.3V
= 34V
0.5
1.5
µA
µA
SHDN
SHDN
5
SHDN Input Voltage High
SHDN Input Voltage Low
2.3
V
V
0.25
correlation with statistical process controls. The LT1934I and LT1934I-1
Note 1: Absolute Maximum Ratings are those values beyond which the life
specifications are guaranteed over the –40°C to 125°C temperature range.
of the device may be impaired.
Note 3: This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the internal power switch.
Note 2: The LT1934E and LT1934E-1 are guaranteed to meet performance
specifications from 0°C to 70°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and
U W
TYPICAL PERFOR A CE 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
L = 47µH
= 25°C
OUT
OUT
L = 150µH
= 25°C
L = 47µH
T = 25°C
A
T
A
T
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
100
90
80
70
60
50
3.0
2.5
2.0
1.5
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
0.1
1
10
100
–50 –25
0
25
50
75 100 125
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
TEMPERATURE (°C)
LOAD CURRENT (mA)
1934 G04
1934 G05
1934 G06
1934f
3
LT1934/LT1934-1
TYPICAL PERFOR A CE CHARACTERISTICS
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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
= 25°C
A
A
8
6
4
2
0
0
0
2
4
6
8
10
12
0.2
0.4
0.8
–50 –25
0
25
50
75
125
0
1.0
1.2
100
0.6
SHDN PIN VOLTAGE (V)
TEMPERATURE (°C)
FEEDBACK PIN VOLTAGE (V)
1934 G09
1934 G07
1934 G08
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
OUT = 5V
V
6.0
5.5
5.0
4.5
4.0
3.5
3.0
8
7
6
5
4
LT1934
LT1934
V = 5V
V
A
= 3.3V
OUT
= 25°C
OUT
T = 25°C
A
T
BOOST DIODE TIED TO OUTPUT
BOOST DIODE TIED TO OUTPUT
TO START
V
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
1934f
4
LT1934/LT1934-1
U
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PI FU CTIO S
BOOST (Pin 1): The BOOST pin is used to provide a drive
voltage, higher than the input voltage, to the internal
bipolar NPN power switch.
SHDN (Pin 4): The SHDN pin is used to put the LT1934 in
shutdown mode. Tie to ground to shut down the LT1934.
Apply 2.3V or more for normal operation. If the shutdown
feature is not used, tie this pin to the VIN pin.
GND(Pin2):TietheGNDpintoalocalgroundplanebelow
the LT1934 and the circuit components. Return the feed-
back divider to this pin.
VIN (Pin 5): The VIN pin supplies current to the LT1934’s
internal regulator and to the internal power switch. This
pin must be locally bypassed.
FB(Pin3):TheLT1934regulatesitsfeedbackpinto1.25V.
Connect the feedback resistor divider tap to this pin. Set
the output voltage according to VOUT = 1.25V (1 + R1/R2)
or R1 = R2 (VOUT/1.25 – 1).
SW (Pin 6): The SW pin is the output of the internal power
switch. Connect this pin to the inductor, catch diode and
boost capacitor.
W
BLOCK DIAGRA
V
IN
V
5
IN
+
C2
+
–
D2
BOOST
1
ON TIME
R
S
Q′
C3
12µs DELAY
Q
L1
OFF TIME
SW
V
6
OUT
1.8µs DELAY
C1
D1
SHDN
ON OFF
V
1.25V
REF
4
+
–
ENABLE
FEEDBACK
COMPARATOR
GND
FB
2
3
R2
R1
1934 BD
1934f
5
LT1934/LT1934-1
U
OPERATIO
(Refer to Block Diagram)
TheLT1934usesBurstModecontrol, combiningbothlow
quiescentcurrentoperationandhighswitchingfrequency,
which result in high efficiency across a wide range of load
currents and a small total circuit size.
the 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
ison, theSWpinvoltageisat10V. Whentheswitchisoff,
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
undervoltage lockout circuits are active, and the current
intotheVIN pinisjust12µA.Astheloadcurrentdischarges
the output capacitor, the voltage at the FB pin falls below
1.25V and the comparator enables the oscillator. The
LT1934 begins to switch, delivering current to the output
capacitor.Theoutputvoltagerises,andwhenitovercomes
the feedback comparator’s hysteresis, the oscillator is
disabled 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.
A rising edge from the off-time one-shot sets the flip-
flop, which turns on the internal NPN power switch. The
switch remains on until either the on-time one-shot trips
or the current limit is reached. A sense resistor and
amplifiermonitorthecurrentthroughtheswitchandresets
If the SHDN pin is grounded, all internal circuits are turned
off and VIN current reduces to the device leakage current,
typically a few nA.
VOUT
50mV/DIV
VSW
10V/DIV
ISW
0.5A/DIV
ILI
0.5A/DIV
1934 F01a
5µs/DIV
Figure 1. Operating Waveforms of the LT1934 Converting
10V to 3.3V at 180mA (Front Page Schematic)
1934f
6
LT1934/LT1934-1
W U U
APPLICATIO S I FOR ATIO
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cycle. The duty cycle is the fraction of time that the internal
switch is on and is determined by the input and output
voltages:
Which One to Use: LT1934 or LT1934-1?
The only difference between the LT1934 and LT1934-1 is
the peak current through the internal switch and the
inductor. Ifyourmaximumloadcurrentislessthan60mA,
usetheLT1934-1. Ifyourmaximumloadishigher, usethe
LT1934; it can supply up to ~300mA.
DC = (VOUT + VD)/(VIN – VSW + VD)
where VD is the forward voltage drop of the catch diode
(~0.4V) and VSW is the voltage drop of the internal switch
(~0.3V at maximum load for the LT1934, ~0.1V for the
LT1934-1). This leads to a minimum input voltage of:
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
inputoftheLT1934-1circuitwillbesmallerandmaybean
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.
V
IN(MIN) = (VOUT + VD)/DCMAX – VD + VSW
with DCMAX = 0.85.
Inductor Selection
A good first choice for the inductor value is:
L = 2.5 • (VOUT + VD) • 1.8µs/ILIM
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
andmaximumloadfor3.3Vand5Vcircuits.Increasingthe
value of the capacitor will lower the output voltage ripple.
Component selection is covered in more detail in the
following sections.
where ILIM is the switch current limit (400mA for the
LT1934 and 120mA for the LT1934-1). This choice pro-
vides 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 ILIM. To keep
efficiency high, the 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
Theminimuminputvoltagerequiredtogenerateaparticu-
lar output voltage is determined by either the LT1934’s
undervoltage lockout of ~3V or by its maximum duty
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
appropriately 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
100µF
47µF
33µF
300mA
250mA
200mA
5V
150µH
68µH
47µH
47µF
33µF
22µF
300mA
250mA
200mA
LT1934-1
3.3V
5V
150µH
100µH
68µH
15µF
10µF
10µF
60mA
45mA
20mA
Detailed Inductor Selection and
Maximum Load Current
The square wave that the LT1934 produces at its switch
pinresultsinatrianglewaveofcurrentintheinductor. The
LT1934 limits the peak inductor current to ILIM. Because
220µH
150µH
100µH
10µF
4.7µF
4.7µF
60mA
45mA
20mA
1934f
7
LT1934/LT1934-1
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APPLICATIO S I FOR ATIO
Table 2. Inductor Vendors
Vendor
Murata
Sumida
Phone
URL
Part Series
Comments
(404) 426-1300 www.murata.com
(847) 956-0666 www.sumida.com
LQH3C
Small, Low Cost, 2mm Height
CR43
CDRH4D28
CDRH5D28
Coilcraft
(847) 639-6400 www.coilcraft.com
DO1607C
DO1608C
DT1608C
Wurth
(866) 362-6673 www.we-online.com WE-PD1, 2, 3, 4
Electronics
the average inductor current equals the load current, the
maximum load current is:
Theinductormustcarrythepeakcurrentwithoutsaturat-
ing excessively. When an inductor carries too much
current, its core material can no longer generate addi-
tional 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.
IOUT(MAX) = IPK – ∆IL/2
where IPK is the peak inductor current and ∆IL is the peak-
to-peak ripple current in the inductor. The ripple current is
determined by the off time, tOFF = 1.8µs, and the inductor
value:
∆IL = (VOUT + VD) • tOFF/L
Inductor vendors provide current ratings for power induc-
tors.Thesearebasedoneitherthesaturationcurrentoron
the RMS current that the inductor can carry without dissi-
patingtoomuchpower. Insomecasesitisnotclearwhich
of these two determine the current rating. Some data
sheets are more thorough and show two current ratings,
one for saturation and one for dissipation. For LT1934
applications,theRMScurrentratingshouldbehigherthan
the load current, while the saturation current should be
higher than the peak inductor current calculated above.
IPK is nominally equal to ILIM. However, there is a slight
delay in the control circuitry that results in a higher peak
current and a more accurate value is:
IPK = ILIM + 150ns • (VIN – VOUT)/L
These expressions are combined to give the maximum
load current that the LT1934 will deliver:
IOUT(MAX) = 350mA + 150ns • (VIN – VOUT)/L – 1.8µs
• (VOUT + VD)/2L (LT1934)
Input Capacitor
IOUT(MAX) = 90mA + 150ns • (VIN – VOUT)/L – 1.8µs
• (VOUT + VD)/2L (LT1934-1)
Step-down regulators draw current from the input supply
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.
The minimum current limit is used here to be conserva-
tive. The third term is generally larger than the second
term, so that increasing the inductor value results in a
higheroutputcurrent.Thisequationcanbeusedtoevalu-
ate a chosen inductor or it can be used to choose L for a
given maximum load current. The simple, single equa-
tion rule given above for choosing L was found by setting
∆IL = ILIM/2.5. This results in IOUT(MAX) ~0.8ILIM (ignor-
ing 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 ∆IL < IPK.
If the input source impedance is high, a larger value
capacitor may be required to keep input ripple low. In this
case, an electrolytic of 10µF or more in parallel with a 1µF
ceramic is a good combination. Be aware that the input
1934f
8
LT1934/LT1934-1
W U U
APPLICATIO S I FOR ATIO
U
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.
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
The output capacitor filters the inductor’s ripple current
and stores energy to satisfy the load current when the
LT1934isquiescent. Inordertokeepoutputvoltageripple
low, the impedance of the capacitor must be low at the
LT1934’s switching frequency. The capacitor’s equivalent
seriesresistance(ESR)determinesthisimpedance.Choose
onewithlowESRintendedforuseinswitchingregulators.
The contribution to ripple voltage due to the ESR is
approximatelyILIM•ESR.ESRshouldbelessthan~150mΩ
for the LT1934 and less than ~500mΩ for the LT1934-1.
Ceramic Capacitors
Ceramic capacitors are small, robust and have very low
ESR. However, ceramic capacitors can cause problems
when used with the LT1934.
Notallceramiccapacitorsaresuitable. X5RandX7Rtypes
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.
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
COUT > 50 • L • (ILIM/VOUT
)
Ceramiccapacitorsarepiezoelectric.TheLT1934’sswitch-
ing frequency depends on the load current, and at light
loadstheLT1934canexcitetheceramiccapacitorataudio
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
requires33µF.Thisvaluecanberelaxedifsmallcircuitsize
is more important than low output ripple.
Sanyo’s POSCAP series in B-case and C-case sizes pro-
vides very good performance in a small package for the
LT1934. Similar performance in traditional tantalum ca-
pacitors requires a larger package (C- or D-case). The
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
1934f
9
LT1934/LT1934-1
W U U
U
APPLICATIO S I FOR ATIO
D2
when used with ceramic capacitors will be lower and may
be acceptable.
C3
BOOST
LT1934
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LT1934. A
ceramic 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 voltage can ring to twice its nominal value,
possibly exceeding 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
SW
BOOST
V
IN
BOOST
OUT
MAX V
V
+ V
OUT
(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
V
1934 F02
V
– V
BOOST
SW
IN
IN
MAX V
2V
BOOST
(2b)
Figure 2. Two Circuits for Generating the Boost Voltage
Schottkydiodeswithlowerreversevoltageratingsusually
have a lower forward drop and may result in higher
efficiency with moderate to high load currents. However,
these diodes also have higher leakage currents. This
leakage current mimics a load current at the output and
can raise the quiescent current of the LT1934 circuit,
especially at elevated temperatures.
maximum duty cycle as outlined above. For proper start-
up, the minimum input voltage is also limited by the boost
circuit.Iftheinputvoltageisrampedslowly,ortheLT1934
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
theworst-casesituationwhereVIN isrampingveryslowly.
Use a Schottky diode (such as the BAT-54) for the lowest
start-up voltage.
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
outputsof3.3Vandabove, thestandardcircuit(Figure2a)
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
efficient because the BOOST pin current comes from a
lower voltage source. You must also be sure that the
maximumvoltageratingoftheBOOSTpinisnotexceeded.
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 VOUT. At higher load currents, the inductor
current is continuous and the duty cycle is limited by the
1934f
The minimum operating voltage of an LT1934 application
is limited by the undervoltage lockout (~3V) and by the
10
LT1934/LT1934-1
W U U
U
APPLICATIO S I FOR ATIO
Minimum Input Voltage VOUT = 3.3V
VIN), then the LT1934’s internal circuitry will pull its
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
zero. However, if the VIN pin is grounded while the output
is held high, then parasitic diodes inside the LT1934 can
pulllargecurrentsfromtheoutputthroughtheSWpinand
the VIN pin. Figure 4 shows a circuit that will run only when
the input voltage is present and that protects against a
shorted or reversed input.
6.0
5.5
5.0
4.5
4.0
3.5
3.0
LT1934
V
= 3.3V
OUT
= 25°C
T
A
BOOST DIODE TIED TO OUTPUT
V
TO START
IN
V
TO RUN
IN
D4
0.1
1
10
100
5
1
V
V
BOOST
LOAD CURRENT (mA)
IN
IN
1934 G12
LT1934
100k
1M
4
6
V
SHDN
SW
OUT
Minimum Input Voltage VOUT = 5V
GND
2
FB
3
8
7
6
5
4
LT1934
V
A
= 5V
OUT
= 25°C
BACKUP
T
BOOST DIODE TIED TO OUTPUT
V
TO START
IN
D4: MBR0530
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
TO RUN
IN
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
groundatonelocation,ideallyatthegroundterminalofthe
output capacitor C1. Additionally, the SW and BOOST
nodes should be kept as small as possible. Finally, keep
theFBnodeassmallaspossiblesothatthegroundpinand
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
applications or in battery backup systems where a battery
or some other supply is diode OR-ed with the LT1934’s
output. If the VIN pin is allowed to float and the SHDN pin
is held high (either by a logic signal or because it is tied to
1934f
11
LT1934/LT1934-1
APPLICATIO S I FOR ATIO
W U U
U
V
SW
V
SW
IN
IN
GND
GND
(5a)
(5b)
I
V
C1
SW
L1
V
SW
IN
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
groundtraceswillshielditfromtheSWandBOOSTnodes.
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
circuit,andthevoltageattheVIN pinoftheLT1934canring
to twice the nominal input voltage, possibly exceeding the
LT1934’s rating and damaging the part. If the input supply
ispoorlycontrolledortheuserwillbepluggingtheLT1934
into an energized supply, the input network should be
designed to prevent this overshoot.
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.
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
1934f
12
LT1934/LT1934-1
W U U
APPLICATIO S I FOR ATIO
U
Figure7showsthewaveformsthatresultwhenanLT1934
circuit is connected to a 24V supply through six feet of
24-gauge twisted pair. The first plot is the response with
a 2.2µF ceramic capacitor at the input. The input voltage
rings as high as 35V and the input current peaks at 20A.
One method of damping the tank circuit is to add another
capacitor with a series resistor to the circuit. In Figure 7b
an aluminum electrolytic capacitor has been added. This
capacitor’s high equivalent series resistance damps the
circuit and eliminates the voltage overshoot. The extra
capacitor improves low frequency ripple filtering and can
slightly improve the efficiency of the circuit, though it is
likely to be the largest component in the circuit. An
alternative solution is shown in Figure 7c. A 1Ω resistor is
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
1934f
13
LT1934/LT1934-1
W U U
U
APPLICATIO S I FOR ATIO
added 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 and less expensive than the electrolytic capaci-
tor. For high 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.
The temperature rise for an LT1934 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 tem-
perature rise is 15°C.
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 VIN to prevent the SW pin from ringing
above VIN during discontinuous mode operation. The 12V
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
1934f
14
LT1934/LT1934-1
U
TYPICAL APPLICATIO S
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
L1
0.1µF
BOOST
150µH
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
1934f
15
LT1934/LT1934-1
TYPICAL APPLICATIO S
U
1.8V Step-Down Converter
D2
0.1µF
L1
33µH
BOOST
V
OUT
V
IN
V
SW
FB
1.8V
IN
3.6V TO 16V
250mA
C2
D1
LT1934
2.2µF
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
1934f
16
LT1934/LT1934-1
U
TYPICAL APPLICATIO S
Standalone 350mA Li-Ion Battery Charger
D2
0.1µF
L1
47µH
1k
10k
BOOST
D3
1k
0.047µF
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
V
V
= 24V
IN
V
IN
= 8V
= 12V
IN
0
2.5
3
3.5
4
4.5
BATTERY VOLTAGE (V)
1934 TA07b
1934f
17
LT1934/LT1934-1
TYPICAL APPLICATIO S
U
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
LT1934
2.2µF
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
1934f
18
LT1934/LT1934-1
U
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
1.4 MIN
1.50 – 1.75
2.80 BSC
3.85 MAX 2.62 REF
(NOTE 4)
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
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
1934f
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
19
LT1934/LT1934-1
U
TYPICAL APPLICATIO
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
D1
LT1934
2.2µF
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
= 3.6V to 25V, V
LT1616
25V, 500mA (I ), 1.4MHz, High Efficiency
V
= 1.25V, I = 1.9mA, I = <1µA,
Q SD
OUT
IN
OUT
OUT
Step-Down DC/DC Converter
ThinSOT Package
LT1676
60V, 440mA (I ), 100kHz, High Efficiency
V
IN
= 7.4V to 60V, V
= 1.24V, I = 3.2mA, I = 2.5µA,
Q SD
OUT
Step-Down DC/DC Converter
S8 Package
LT1765
25V, 2.75A (I ), 1.25MHz, High Efficiency
Step-Down DC/DC Converter
V
= 3V to 25V, V
= 1.2V, I = 1mA, I = 15µA,
OUT Q SD
OUT
IN
S8, TSSOP16E Packages
LT1766
60V, 1.2A (I ), 200kHz, High Efficiency
Step-Down DC/DC Converter
V
IN
= 5.5V to 60V, V = 1.2V, I = 2.5mA, I = 25µA,
OUT
OUT
Q
SD
TSSOP16/E Package
= 3V to 25V; V = 1.2V, I = 1mA, I = 6µA,
OUT Q SD
LT1767
25V, 1.2A (I ), 1.25MHz, High Efficiency
V
IN
OUT
Step-Down DC/DC Converter
MS8/E Packages
LT1776
40V, 550mA (I ), 200kHz, High Efficiency
Step-Down DC/DC Converter
V
= 7.4V to 40V; V
= 1.24V, I = 3.2mA, I = 30µA,
OUT Q SD
OUT
IN
N8, S8 Packages
LTC®1877
LTC1879
600mA (I ), 550kHz, Synchronous
Step-Down DC/DC Converter
V
= 2.7V to 10V; V
= 0.8V, I = 10µA, I = <1µA,
Q SD
OUT
IN
OUT
OUT
OUT
MS8 Package
1.2A (I ), 550kHz, Synchronous
V
IN
= 2.7V to 10V; V
= 0.8V, I = 15µA, I = <1µA,
Q SD
OUT
Step-Down DC/DC Converter
TSSOP16 Package
LT1956
60V, 1.2A (I ), 500kHz, High Efficiency
V
IN
= 5.5V to 60V, V
= 1.2V, I = 2.5mA, I = 25µA,
Q SD
OUT
Step-Down DC/DC Converter
TSSOP16/E Package
LTC3405/LTC3405A
LTC3406/LTC3406B
LTC3411
300mA (I ), 1.5MHz, Synchronous
Step-Down DC/DC Converter
V
= 2.7V to 6V, V
= 0.8V, I = 20µA, I = <1µA,
OUT Q SD
OUT
IN
ThinSOT Package
600mA (I ), 1.5MHz, Synchronous
V
IN
= 2.5V to 5.5V, V
= 0.6V, I = 20µA, I = <1µA,
OUT Q SD
OUT
Step-Down DC/DC Converter
ThinSOT Package
1.25A (I ), 4MHz, Synchronous
V
IN
= 2.5V to 5.5V, V
= 0.8V, I = 60µA, I = <1µA,
Q SD
OUT
OUT
OUT
OUT
Step-Down DC/DC Converter
MS Package
LTC3412
2.5A (I ), 4MHz, Synchronous
V
IN
= 2.5V to 5.5V, V
= 0.8V, I = 60µA, I = <1µA,
Q SD
OUT
Step-Down DC/DC Converter
TSSOP16E Package
LTC3430
60V, 2.75A (I ), 200kHz, High Efficiency
V
IN
= 5.5V to 60V, V
= 1.2V, I = 2.5mA, I = 30µA,
Q SD
OUT
Step-Down DC/DC Converter
TSSOP16E Package
1934f
LT/TP 0703 1K • PRINTED IN USA
20 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
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LINEAR TECHNOLOGY CORPORATION 2002
相关型号：
LT1934EDCB#TRMPBF
LT1934 - Micropower Step-Down Switching Regulators in ThinSOT; Package: DFN; Pins: 6; Temperature Range: -40°C to 85°C
Linear
LT1934EDCB#TRPBF
LT1934 - Micropower Step-Down Switching Regulators in ThinSOT; Package: DFN; Pins: 6; Temperature Range: -40°C to 85°C
Linear
LT1934EDCB-1
IC 0.16 A SWITCHING REGULATOR, PDSO6, 2 X 3 MM, 0.80 MM HEIGHT, PLASTIC, MO-229, DFN-6, Switching Regulator or Controller
Linear
LT1934EDCB-1#PBF
LT1934 - Micropower Step-Down Switching Regulators in ThinSOT; Package: DFN; Pins: 6; Temperature Range: -40°C to 85°C
Linear
LT1934EDCB-1#TR
IC 0.16 A SWITCHING REGULATOR, PDSO6, 2 X 3 MM, 0.80 MM HEIGHT, PLASTIC, MO-229, DFN-6, Switching Regulator or Controller
Linear
LT1934EDCB-1#TRMPBF
LT1934 - Micropower Step-Down Switching Regulators in ThinSOT; Package: DFN; Pins: 6; Temperature Range: -40°C to 85°C
Linear
LT1934EDCB-1#TRPBF
LT1934 - Micropower Step-Down Switching Regulators in ThinSOT; Package: DFN; Pins: 6; Temperature Range: -40°C to 85°C
Linear
LT1934ES6#TRM
LT1934 - Micropower Step-Down Switching Regulators in ThinSOT; Package: SOT; Pins: 6; Temperature Range: -40°C to 85°C
Linear
LT1934ES6#TRPBF
LT1934 - Micropower Step-Down Switching Regulators in ThinSOT; Package: SOT; Pins: 6; Temperature Range: -40°C to 85°C
Linear
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