LT1432CS8-3.3 [Linear]
3.3V High Efficiency Step-Down Switching Regulator Controller; 3.3V高效率降压型开关稳压器控制器
| 型号： | LT1432CS8-3.3 |
| 厂家： | 
Linear |
| 描述： | 3.3V High Efficiency Step-Down Switching Regulator Controller |
| 文件： | 总8页 (文件大小：222K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1432-3.3
3.3V High Efficiency Step-Down
Switching Regulator Controller
U
DESCRIPTIO
EATURE
S
F
The LT®1432-3.3 is a control chip designed to operate
with the LT1171/LT1271 family of switching regulators to
makeaveryhighefficiency3.3Vstep-down(buck)switch-
ing regulator. A minimum of external components is
needed.
■
■
■
■
■
■
■
■
Accurate Preset 3.3V Output
Up to 87% Efficiency
Optional Burst ModeTM Operation for Light Loads
Can Be Used with Many LTC Switching ICs
Accurate Ultra-Low-Loss Current Limit
Operates with Inputs from 4.5V to 30V
Shutdown Mode Draws Only 15µA
Uses Small 30µH Inductor
Included is an accurate current limit which uses only
60mV sense voltage and uses “free” PC board trace
material for the sense resistor. Logic controlled electronic
shutdown mode draws only 15µA battery current. The
switching regulator operates down to 4.5V input.
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PPLICATI
Laptop and Palmtop Computers
Portable Data-Gathering Instruments
S
A
The LT1432-3.3 has a logic controlled Burst Mode operation
to achieve high efficiency at very light load currents (0mA to
100mA) such as memory keep-alive. In normal switching
mode, the standby power loss is about 30mW, limiting
efficiency at light loads. In Burst Mode operation, standby
loss is reduced to approximately 11mW. Output current in
this mode is typically in the 5mA to 100mA range.
■
■
The LT1432-3.3 is available in 8-pin SO and PDIP pack-
ages. The LT1171/LT1271 is also available in surface
mount DD packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATI
D2
1N5818
V
IN
10µH
3A
V
SW
V
IN
+
Efficiency
C1
330µF
35V
LT1271
+
OPTIONAL
100
FB
100µF
OUTPUT
V
GND
C
LT1271, L = 30µH
16V
FILTER
D2**
C6
V
IN
= 7V
0.02µF
D2 CONNECTED
TO OUTPUT
90
80
70
C3
+
†
L1
30µH
C5
0.03µF
R2*
0.013Ω
10µF
V
3.3V
3A
***
OUT
TANT
D2 CONNECTED
TO INPUT
×
+
D1
C2
MBR330p
+
390µF
16V
V
V
DIODE
C
Burst Mode OPERATION
(USE mA SCALE)
V
V
V
IN
LIM
LT1432-3.3
GND
MODE
OUT
MODE LOGIC
220pF
*R2 IS MADE FROM PC BOARD
COPPER TRACES.
60
0
0
3A
60mA
1A
2A
**OPTIONAL CONNECTION FOR D2.
20mA
40mA
†
<0.3V = NORMAL MODE
>2.5V = SHUTDOWN
OPEN = Burst Mode
OPERATION
FOR CIRCUITS WHICH DO NOT USE
Burst Mode OPERATION, C5 MAY
BE PARALLEL WITH A 680Ω, 0.1µF
IN SERIES TO GIVE WIDE PHASE MARGIN ***MAXIMUM CURRENT IS DETERMINED
WITH DIFFERENT SWITCHING ICs AND
OUTPUT CAPACITORS
EFFICIENCY IS HIGHER, BUT MINIMUM
LT1432-3.3 TA02
V INCREASES. SEE APPLICATION
IN
INFORMATION SECTION.
BY THE CHOICE OF LT1071 FAMILY MAIN SWITCHER IC.
SEE APPLICATION INFORMATION SECTION.
LT1432-3.3 TA01
Figure 1. High Efficiency 5V Buck Converter
1
LT1432-3.3
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ABSOLUTE AXI U RATI GS
PACKAGE RDER I FOR ATIO
VIN Pin .................................................................... 30V
V+ Pin ..................................................................... 40V
VC ........................................................................... 35V
VLIM and VOUT Pins................................................... 7V
Diode Pin Voltage ................................................... 30V
Mode Pin Current (Note 2) ..................................... 1mA
Operating Temperature Range .................... 0°C to 70°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
TOP VIEW
ORDER PART
NUMBER
1
2
3
4
8
7
6
5
MODE
GND
V
LIM
V
OUT
LT1432CN8-3.3
LT1432CS8-3.3
V
C
V
IN
+
DIODE
V
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 100°C, θJA = 150°C/W (N8)
TJMAX = 100°C, θJA = 170°C/W (S8)
Consult factory for Military and Industrial grade parts.
ELECTRICAL CHARACTERISTICS
VC = 4V, VIN = 4V, V+ = 8V, VDIODE = Open, VLIM = VOUT, VMODE = 0V, TJ = 25°C
Device is in standard test loop unless otherwise noted.
PARAMETER
CONDITIONS
V Current = 220µA
MIN
TYP
MAX UNITS
Regulated Output Voltage
Output Voltage Line Regulation
Input Supply Current (Note 1)
Quiescent Output Load Current
Mode Pin Current
●
●
●
3.24
3.30
5
3.36
20
V
mV
mA
mA
C
V
IN
V
IN
= 4V to 30V
+
= 4V to 30V, V = V + 5V, V = V + 1V
0.3
0.9
0.5
1.2
IN
C
IN
V
MODE
V
MODE
= 0V (Current Is Out of Pin)
= 3.3V (Shutdown)
●
●
30
15
50
30
µA
µA
Mode Pin Threshold Voltage
(Normal to Burst)
I
= 10µA (Out of Pin)
●
0.6
0.9
1.5
V
MODE
V Pin Saturation Voltage
V
V
V
= 3.6V (Forced)
= 3.6V (Forced)
= 3.0V (Forced)
●
●
●
0.25
0.8
60
0.45
1.5
100
64
V
mA
µA
C
OUT
OUT
OUT
V Pin Maximum Sink Current
C
0.45
35
V Pin Source Current
C
Current Limit Sense Voltage (Note 3)
Device in Current Limit Loop
56
60
mV
µA
V
LIM
Pin Current
Device in Current Limit Loop
(Current Is Out of Pin)
●
30
45
70
+
Supply Current in Shutdown
V
MODE
> 3V, V < 30V, V and V = 0V
15
100
3.30
0.5
45
60
µA
IN
C
Burst Mode Operation Output Ripple
Device in Burst Test Circuit
mV
p-p
Burst Mode Operation Average Output Voltage Device in Burst Test Circuit
●
●
●
3.15
30
3.45
0.65
V
Clamp Diode Forward Voltage
Start-up Drive Current
I = 1mA, All Other Pins Open
F
V
V
= 1.5V (Forced), V = 4V to 26V,
mA
OUT
IN
+
V = V – 1V, V = V – 1.5V
IN
C
IN
Restart Time Delay
(Note 4)
0.7
1.2
10
ms
Transconductance, Output to V Pin
I = 150µA to 250µA
C
●
2700
3600
5000
µmho
C
2
LT1432-3.3
ELECTRICAL CHARACTERISTICS
Operating parameters in standard circuit configuration.
IN = 7V, IOUT = 0, unless otherwise noted. These parameters guaranteed where indicated, but not tested.
V
PARAMETER
CONDITIONS
MIN
TYP
MAX UNITS
Burst Mode Operation Quiescent Input Supply Current
Burst Mode Operation Output Ripple Voltage
1.6
2.2
mA
I
I
= 0
80
mV
OUT
OUT
p-p
p-p
= 50mA
120
mV
Normal Mode Equivalent Input Supply Current
Normal Mode Minimum Operating Input Voltage
Extrapolated from I
= 20mA
3.0
4.5
mA
V
OUT
100mA < I
< 1.5A
OUT
Burst Mode Operation Minimum Operating Input Voltage 5mA < I
< 50mA
4.1
V
OUT
Efficiency
Normal Mode
I
= 0.5A
= 25mA
86
70
%
%
OUT
OUT
Burst Mode Operation I
Load Regulation
Normal Mode
50mA < I
< 2A
5
30
15
mV
mV
OUT
Burst Mode Operation 0 < I
< 50mA
OUT
The
● denotes specifications which apply over the full operating
Note 3: Current limit sense voltage temperature coefficient is +0.33%/°C
to match TC of copper trace material.
temperature range.
Note 1: Does not include current drawn by the power IC. See operating
parameters in standard circuit.
Note 4: V
pin switched from 3.6V to 3.0V.
OUT
Note 2: Breakdown voltage on the Mode pin is 7V. External current must
be limited to value shown.
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EQUIVALE T SCHE ATIC
D2
V
IN
V
V
SW
IN
OPTIONAL
CONNECTION
OF D2
LT1271
FB
GND
V
C
3.3V
V
OUT
V
LIM
1
2
60mV
+
–
+
V
IN
V
C
DIODE
5
V
3
4
6
S1**
+
–
S3*
*
S3 IS CLOSED ONLY DURING START-UP.
S2**
** S1 AND S2 ARE SHOWN IN NORMAL
MODE. REVERSE FOR Burst Mode
OPERATION.
MODE
CONTROL
7
GND
MODE
8
LT1432-3.3 F02
Figure 2
3
LT1432-3.3
TYPICAL PERFOR A CE CHARACTERISTICS
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Minimum Input Voltage to Start –
Normal Mode (Diode to Input)
Efficiency vs Input Voltage
Efficiency vs Load Current
6.5
6.0
5.5
5.0
4.5
4.0
100
90
95
90
85
80
T
= 25°C
T
= 25°C
IN
T = 25°C
J
J
J
LT1271, L = 50µH
V
= 7V
DIODE TO OUTPUT
LT1270
LT1271
DIODE
80
DIODE TO INPUT
= 1A
TO INPUT
I
OUT
LT1270
70
LT1171
LT1271
60
75
0
1
2
3
4
5
0
5
10
15
20
25
30
0
0.5
1.0
1.5
2.0
2.5
3.0
INPUT VOLTAGE (V)
LOAD CURRENT (A)
OUTPUT CURRENT (A)
LT1432-3.3 G03
LT1432-3.3 G01
LT1432-3.3 G02
Minimum Input Voltage –
Normal Mode (Diode to Output)
Minimum Running Voltage –
Normal Mode*
Burst Mode Operation Minimum
Input Voltage
9.0
8.0
7.0
5.5
5.0
4.5
5.5
5.0
4.5
4.0
3.5
T
= 25°C
T = 25°C
T
J
= 25°C
J
J
LT1171
LT1271
LT1270
LT1171
LT1271
6.0
5.0
4.0
4.0
3.5
3.0
DIODE
TO INPUT
0
1
2
3
4
5
0
1
2
3
4
5
0
10
20
30
40
50
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
LOAD CURRENT (mA)
LT1432-3.3 G04
LT1432-3.3 G05
LT1432-3.3 G06
*SEE MINIMUM INPUT VOLTAGE TO START
Shutdown Current vs Input
Voltage
Current Limit Sense Voltage*
Battery Current in Shutdown*
50
40
30
20
80
70
60
50
40
40
30
20
10
0
T
= 25°C
J
V
= 30V
= 6V
IN
V
IN
10
0
0
10
15
20
25
30
5
50
75
0
100
50
TEMPERATURE (°C)
75
25
0
100
25
INPUT VOLTAGE (V)
JUNCTION TEMPERATURE (°C)
LT1432-3.3 G9
LT1432-3.3 G07
LT1432-3.3 G08
* TEMPERATURE COEFFICIENT OF SENSE VOLTAGE IS
DESIGNED TO TRACK COPPER RESISTANCE.
*DOES NOT INCLUDE LT1271 SWITCH LEAKAGE.
4
LT1432-3.3
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TYPICAL PERFOR A CE CHARACTERISTICS
No Load Battery Current in Burst
Mode Operation
Transconductance – VOUT to VC
Current
Incremental Battery Current * in
Burst Mode Operation
2.0
1.5
1.0
0.5
0
5
4
3
2
1
0
5000
4000
3000
2000
1000
T
J
= 25°C
T = 25°C
J
∆I(V PIN)
C
Gm =
∆V
OUT
0
5
10
15
20
25
0
5
10
15
20
25
50
75
0
100
25
BATTERY VOLTAGE (V)
BATTERY VOLTAGE (V)
JUNCTION TEMPERATURE (°C)
LT1432-3.3 G10
LT1432-3.3 G11
LT1432-3.3 G12
* TO CALCULATE TOTAL BATTERY CURRENT IN Burst
Mode OPERATION, MULTIPLY LOAD CURRENT BY
INCREMENTAL FACTOR AND ADD NO-LOAD CURRENT.
Burst Mode Operation Load
Regulation
Mode Pin Current
Line Regulation
60
40
25
0
40
T
= 25°C
J
T
= 25°C
IN
T = 25°C
J
J
V
= 7V
20
0
20
NORMAL MODE
–25
–50
–75
0
Burst Mode OPERATION
–20
–40
–20
–40
MODE DRIVE MUST
SINK ≈ 30µA AT 0V
0
2
4
6
8
10
0
20
40
60
80
100
10
15
0
20
5
MODE PIN VOLTAGE (V)
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
LT1432-3.3 G14
LT1432-3.3 G15
LT1432-3.3 G13
Restart Load Current
Restart Time Delay
Start-up Switch Characteristics
5
0
40
30
20
10
0
4
3
2
1
0
T = 25°C
J
V
= 4.5V
OUT
NOTE VERTICAL AND
HORIZONTAL SCALE
CHANGES AT 0,0
–20
–40
–60
–80
–2
–1
0
10
20
30
50
75
0
100
25
50
JUNCTION TEMPERATURE (°C)
0
75
100
25
+
V
TO V VOLTAGE
JUNCTION TEMPERATURE (°C)
IN
LT1432-3.3 G18
LT1432-3.3 G16
LT1432-3.3 G16
5
LT1432-3.3
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MoreapplicationsinformationontheLT1432-3.3isavailable
in the LT1432 data sheet.
current limiting, micropower shutdown, and dual mode
operation for high conversion efficiency with both heavy and
very light loads.
Basic Circuit Description
The circuit in Figure 1 is a basic 3.3V positive buck
converter which can operate with input voltage from 4.5V
to 30V. The power switch is located between the VSW pin
and GND pin on the LT1271. Its current and duty cycle are
controlled by the voltage on the VC pin with respect to the
GND pin. This voltage ranges from 1V to 2V as switch
current increases from zero to full-scale. Correct output
voltage is maintained by the LT1432-3.3 which has an
internal reference and error amplifier (see Equivalent
Schematic in Figure 2). The amplifier output is level
shifted with an internal open collector NPN to drive the VC
pin of the switcher. The normal resistor divider feedback
to the switcher feedback pin cannot be used because the
feedback pin is referenced to the GND pin, which is
switching up and down. The Feedback pin (FB) is simply
bypassed with a capacitor. This forces the switcher VC pin
to swing high with about 200µA sourcing capability. The
LT1432-3.3 VC pin then sinks this current to control the
loop. Transconductance from the regulator output to the
VC pin current is controlled to approximately 3600µmhos
by local feedback around the LT1432-3.3 error amplifier
(S2 closed in Figure 2). This is done to simplify frequency
compensation of the overall loop. A word of caution about
the FB pin bypass capacitor (C6): this capacitor value is
very non-critical, but the capacitor must be connected
directly to the GND pin or tab of the switcher to avoid
differential spikes created by fast switch currents flow-
ing in the external PCB traces. This is also true for the
frequency compensation capacitor C5. C5 forms the
dominant loop pole.
The LT1432-3.3 is a dedicated 3.3V buck converter driver
chipintendedtobeusedwithanICswitcherfromtheLT1171/
LT1271 family. This family of current mode switchers in-
cludes current ratings from 1.25A to 10A, and switching
frequencies from 40kHz to 100kHz as shown in the table
below.
SWITCH
CURRENT
OUTPUT CURRENT IN
BUCK CONVERTER
DEVICE
FREQUENCY
LT1270A
LT1270
LT1170
LT1070
LT1269
LT1271
LT1171
LT1071
LT1172
LT1072
10A
8A
5A
5A
4A
60kHz
60kHz
100kHz
40kHz
100kHz
60kHz
100kHz
40kHz
100kHz
40kHz
7.5A
6A
3.75A
3.75A
3A
4A
3A
2.5A
2.5A
1.25A
1.25A
1.8A
1.8A
0.9A
0.9A
The maximum load current which can be delivered by these
chips in a buck converter is approximately 75% of their
switch current rating. This is partly due to the fact that buck
converters must operate at very high duty cycles when input
voltage is low. The current mode nature of the LT1271 family
requires an internal reduction of peak current limit at high
dutycycles,sothesedevicesareratedatonly80%oftheirfull
current rating when duty cycle is 80%. A second factor is
inductor ripple current, half of which subtracts from maxi-
mumavailableloadcurrent.TheLT1271familywasoriginally
intended for topologies which have the negative side of the
switch grounded, such as boost converters. It has an ex-
tremely efficient quasi-saturating NPN switch which mimics
the linear resistive nature of a MOSFET but consumes much
less die area. Driver losses are kept to a minimum with a
patentedadaptiveantisatdrivethatmaintainsaforcedbetaof
40 over a wide range of switch currents. This family is
attractive for high efficiency buck converters because of the
low switch loss, but to operate as a positive buck converter,
the GND pin of the IC must be floated to act as the switch
output node. This requires a floating power supply for the
chip and some means for level shifting the feedback signal.
The LT1432-3.3 performs these functions as well as adding
A floating power supply for the switcher is generated by D2
and C3 which peak detect the input voltage during switch off
time.Thisisdifferentthanthe5VversionoftheLT1432which
connects the anode of the diode to the output rather than the
input. The output connection is more efficient because the
floating voltage is a constant 5V (or 3.3V), independent of
input voltage, but in the case of the 3.3V circuit, minimum
required input voltage for starting is several volts higher (see
the Typical Performance Characteristics curves). When the
diode is connected to the input, the suggested type is a
6
LT1432-3.3
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Schottky 1N5818. Diode type is more critical for the output
connection because the high capacitance of Schottky diodes
createsnarrowoutputspikes.Thesespikeswillbeeliminated
if a secondary output filter is used or if there is sufficient lead
length between the regulator output and the load bypass
capacitors. Low capacitance diodes like the 1N4148 do not
createlargespikes,buttheirhighforwardresistancerequires
even higher input voltage to start.
pulses. This maximizes efficiency at light load by eliminating
quiescent current in the switching IC during the period
between bursts.
The result of pulsating currents into the output capacitor
is that output ripple amplitude increases and ripple fre-
quency becomes a function of load current. The typical
output ripple in Burst Mode operation is 100mVp-p, and
ripple frequency can vary from 50Hz to 2kHz. This is not
normally a problem for the logic circuits which are kept
alive during sleep mode.
D1, L1 and C2 act as the conventional catch diode and
output filter of the buck converter. These components
should be selected carefully to maintain high efficiency
andacceptableoutputripple. SeetheoriginalLT1432(5V)
data sheet for detailed discussions of these parts.
Some thought must be given to proper sequencing be-
tween normal mode and Burst Mode operation. A heavy
(>100mA) load in Burst Mode operation can cause exces-
sive output ripple, and an abnormally light load (10mA to
30mA, see Figure 3) in normal mode can cause the
regulator to revert to a quasi-Burst Mode operation that
also has higher output ripple. The worst condition is a
sudden, large increase in load current (>100mA) during
this quasi-Burst Mode operation or just after a switch
from Burst Mode operation to normal mode. This can
cause the output to sag badly while the regulator is
establishing normal mode operation (≈100µs). To avoid
problems, it is suggested that the power-down sequence
consist of reducing load current to below 100mA, but
greater than the minimum for normal mode, then switch-
ing to Burst Mode operation, followed by a reduction of
load current to the final sleep value. Power-up would
consist of increasing the load current to the minimum for
Current limiting is performed by R2. Sense voltage is only
60mV to maintain high efficiency. This also reduces the
value of the sense resistor enough to utilize a printed
circuitboardtraceasthesenseresistor. Thesensevoltage
has a positive temperature coefficient of 0.33%/°C to
match the temperature coefficient of copper.
The basic regulator has three different operating modes,
definedbytheModepindrive.Normaloperationoccurswhen
the Mode pin is grounded. A low quiescent current Burst
Mode operation can be initiated by floating the Mode pin.
Input supply current is typically 1.3mA in this mode, and
output ripple voltage is 100mVp-p. Pulling the Mode pin
above 2.5V forces the entire regulator into micropower
shutdown where it typically draws less than 20µA.
50
Burst Mode Operation
NORMAL MODE
T
= 25°C
J
Burst Mode operation is initiated by allowing the Mode pin to
float, where it will assume a DC voltage of approximately 1V.
If AC pickup from surrounding logic lines is likely, the Mode
pin should be bypassed with a 200pF capacitor. Burst Mode
operationisusedtoreducequiescentoperatingcurrentwhen
the regulator output current is very low, as in sleep mode in
a lap-top computer. In this mode, hysteresis is added to the
error amplifier to make it switch on and off, rather than
maintain a constant amplifier output. This forces the switch-
ing IC to either provide a rapidly increasing current or to go
into full micropower shutdown. Current is delivered to the
output capacitor in pulses of higher amplitude and low duty
cycle rather than a continuous stream of low amplitude
40
30
20
10
0
DIODE TO OUTPUT (1N5818)
DIODE TO INPUT (1N5818)
4
5
6
7
8
9
INPUT VOLTAGE (V)
LT1432-3.3 • F03
Figure 3. Minimum Normal Mode Load Current
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.
7
LT1432-3.3
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A
normalmode, thenswitchingtonormalmode, pausingfor
1ms, followed by return to full load.
Full Shutdown
When the Mode pin is driven high, full shutdown of the
regulator occurs. Regulator input current will then consist
of the LT1432 shutdown current (≈15µA) plus the switch
leakage of the switching IC (≈1µA to 25µA). Mode input
current (≈15µA at 5V) must also be considered. Start-up
from shutdown can be in either normal or Burst Mode
operation, but one should always check start-up over-
shoot, especially if the output capacitor or frequency
compensation components have been changed.
If this sequence is not possible, an alternative is to
increase the output capacitor to > 680µF. This modifica-
tion will often allow the power-down sequence to consist
of simultaneous turn-off of load current and switch to
Burst Mode operation. Power-up is accomplished by
switching to normal mode and simultaneously increasing
loadcurrenttothelowestpossiblevalue(30mAto500mA),
followed by a short pause and return to full load current.
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Dimensions in inches (millimeters) unless otherwise noted.
PACKAGE DESCRIPTIO
N8 Package
8-Lead Plastic DIP
0.400*
(10.160)
MAX
0.130 ± 0.005
(3.302 ± 0.127)
0.300 – 0.325
0.045 – 0.065
(1.143 – 1.651)
(7.620 – 8.255)
8
1
7
6
5
0.065
(1.651)
TYP
0.009 – 0.015
(0.229 – 0.381)
0.255 ± 0.015*
(6.477 ± 0.381)
0.125
(3.175)
MIN
0.005
(0.127)
MIN
0.015
(0.380)
MIN
+0.025
–0.015
0.325
2
4
3
+0.635
8.255
(
)
–0.381
0.100 ± 0.010
(2.540 ± 0.254)
0.018 ± 0.003
(0.457 ± 0.076)
N8 0695
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
S8 Package
8-Lead Plastic SOIC
0.189 – 0.197*
(4.801 – 5.004)
7
5
8
6
0.010 – 0.020
(0.254 – 0.508)
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
0.016 – 0.050
0.406 – 1.270
0.050
(1.270)
BSC
0.014 – 0.019
(0.355 – 0.483)
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
SO8 0695
1
2
3
4
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
5V Regulated Output Voltage
High Efficiency Synchronous Step-Down Switching Regulator Adjustable and Fixed 5V or 3.3V Outputs
LTC1148
LT1432
LT1507
High Efficiency Step-Down Switching Regulator Controller
1.5A, 500kHz Step-Down Switching Regulator
Fixed Frequency PWM for Low Input Voltages from 4.5V to 12V
LT/GP 0895 2K REV A • PRINTED IN USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
8
●
●
LINEAR TECHNOLOGY CORPORATION 1992
(408) 432-1900 FAX: (408) 434-0507 TELEX: 499-3977
相关型号：
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