LT1432-3.3 - 3.3V High Efficiency Step-Down Switching Regulator Controller

LT1432-3.3
3.3V High Efficiency Step-Down
Switching Regulator Controller
OBSOLETE:
FOR INFORMATION PURPOSES ONLY
Contact Linear Technology for Potential Replacement
FEATURES
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DESCRIPTIO
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
APPLICATI
The LT ®1432-3.3 is a control chip designed to operate
with the LT1171/LT1271 family of switching regulators to
make a very high efficiency 3.3V step-down (buck) switching regulator. A minimum of external components is
needed.
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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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.
Laptop and Palmtop Computers
Portable Data-Gathering Instruments
The LT1432-3.3 is available in 8-pin SO and PDIP packages. 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.
TYPICAL APPLICATI
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D2
1N5818
VIN
10µH
3A
VIN
VSW
C1
330µF
35V
LT1271
C6
0.02µF
FB
VC
GND
C5†
0.03µF
D1
MBR330p
<0.3V = NORMAL MODE
>2.5V = SHUTDOWN
OPEN = Burst Mode
OPERATION
D2**
+
L1
30µH
VC
DIODE
R2*
0.013Ω
LT1432-3.3
V+
+
Efficiency
OPTIONAL
OUTPUT
FILTER
100
LT1271, L = 30µH
VIN = 7V
D2 CONNECTED
TO OUTPUT
90
+
VIN
MODE LOGIC
220pF
C3
10µF
TANT
100µF
16V
×
C2
390µF
16V
VOUT***
3.3V
3A
VLIM
EFFICIENCY (%)
+
D2 CONNECTED
TO INPUT
80
Burst Mode OPERATION
(USE mA SCALE)
70
VOUT
MODE
GND
*R2 IS MADE FROM PC BOARD
COPPER TRACES.
**OPTIONAL CONNECTION FOR D2.
† FOR CIRCUITS WHICH DO NOT USE
EFFICIENCY IS HIGHER, BUT MINIMUM
SEE APPLICATION
V
Burst Mode OPERATION, C5 MAY
IN INCREASES.
INFORMATION SECTION.
BE PARALLEL WITH A 680Ω, 0.1µF
IN SERIES TO GIVE WIDE PHASE MARGIN ***MAXIMUM CURRENT IS DETERMINED
BY THE CHOICE OF LT1071 FAMILY MAIN SWITCHER IC.
WITH DIFFERENT SWITCHING ICs AND
SEE APPLICATION INFORMATION SECTION.
OUTPUT CAPACITORS
60
0
0
1A
20mA
2A
40mA
3A
60mA
LT1432-3.3 TA02
LT1432-3.3 TA01
Figure 1. High Efficiency 5V Buck Converter
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LT1432-3.3
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PACKAGE/ORDER 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
ORDER PART
NUMBER
TOP VIEW
VLIM 1
8
MODE
VOUT 2
7
GND
VIN 3
6
VC
V+
5
DIODE
4
N8 PACKAGE
8-LEAD PDIP
LT1432CN8-3.3
LT1432CS8-3.3
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
Regulated Output Voltage
VC Current = 220µA
●
Output Voltage Line Regulation
VIN = 4V to 30V
●
Input Supply Current (Note 1)
VIN = 4V to 30V, V + = VIN + 5V, VC = VIN + 1V
●
MIN
TYP
MAX
3.24
3.30
3.36
5
20
mV
0.3
0.5
mA
0.9
1.2
mA
30
15
50
30
µA
µA
0.9
1.5
V
0.25
0.45
V
0.8
1.5
mA
Quiescent Output Load Current
Mode Pin Current
VMODE = 0V (Current Is Out of Pin)
VMODE = 3.3V (Shutdown)
●
●
Mode Pin Threshold Voltage
(Normal to Burst)
IMODE = 10µA (Out of Pin)
●
VC Pin Saturation Voltage
VOUT = 3.6V (Forced)
●
VC Pin Maximum Sink Current
VOUT = 3.6V (Forced)
●
VC Pin Source Current
VOUT = 3.0V (Forced)
●
Current Limit Sense Voltage (Note 3)
Device in Current Limit Loop
VLIM Pin Current
Device in Current Limit Loop
(Current Is Out of Pin)
Supply Current in Shutdown
Burst Mode Operation Output Ripple
0.6
0.45
V
35
60
100
µA
56
60
64
mV
30
45
70
µA
VMODE > 3V, VIN < 30V, VC and V + = 0V
15
60
Device in Burst Test Circuit
100
●
3.15
µA
mVp-p
Burst Mode Operation Average Output Voltage
Device in Burst Test Circuit
●
Clamp Diode Forward Voltage
IF = 1mA, All Other Pins Open
●
Start-up Drive Current
VOUT = 1.5V (Forced), VIN = 4V to 26V,
V + = VIN – 1V, VC = VIN – 1.5V
●
30
Restart Time Delay
(Note 4)
0.7
1.2
10
Transconductance, Output to VC Pin
IC = 150µA to 250µA
●
2700
3600
5000
2
UNITS
3.30
3.45
V
0.5
0.65
V
45
mA
ms
µmho
LT1432-3.3
ELECTRICAL CHARACTERISTICS
Operating parameters in standard circuit configuration.
VIN = 7V, IOUT = 0, unless otherwise noted. These parameters guaranteed where indicated, but not tested.
PARAMETER
CONDITIONS
MIN
Burst Mode Operation Quiescent Input Supply Current
TYP
MAX
1.6
2.2
UNITS
mA
Burst Mode Operation Output Ripple Voltage
IOUT = 0
IOUT = 50mA
80
120
mVp-p
mVp-p
Normal Mode Equivalent Input Supply Current
Extrapolated from IOUT = 20mA
3.0
mA
Normal Mode Minimum Operating Input Voltage
100mA < IOUT < 1.5A
Burst Mode Operation Minimum Operating Input Voltage
5mA < IOUT < 50mA
Efficiency
Normal Mode
IOUT = 0.5A
Burst Mode Operation IOUT = 25mA
Normal Mode
50mA < IOUT < 2A
Burst Mode Operation 0 < IOUT < 50mA
Load Regulation
The ● denotes specifications which apply over the full operating
temperature range.
Note 1: Does not include current drawn by the power IC. See operating
parameters in standard circuit.
Note 2: Breakdown voltage on the Mode pin is 7V. External current must
be limited to value shown.
4.5
V
4.1
V
86
70
%
%
5
30
15
mV
mV
Note 3: Current limit sense voltage temperature coefficient is +0.33%/°C
to match TC of copper trace material.
Note 4: VOUT pin switched from 3.6V to 3.0V.
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EQUIVALE T SCHE ATIC
D2
VIN
VSW
VIN
LT1271
VC
OPTIONAL
CONNECTION
OF D2
FB
GND
3.3V
VLIM
1
2
+
–
VOUT
60mV
3
VIN
4
V+
6
VC
5
DIODE
S1**
+
S3*
–
* S3 IS CLOSED ONLY DURING START-UP.
** S1 AND S2 ARE SHOWN IN NORMAL
MODE. REVERSE FOR Burst Mode
OPERATION.
S2**
MODE
CONTROL
7
8
MODE
GND
LT1432-3.3 F02
Figure 2
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LT1432-3.3
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TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Input Voltage
Minimum Input Voltage to Start –
Normal Mode (Diode to Input)
Efficiency vs Load Current
100
6.5
95
TJ = 25°C
LT1271, L = 50µH
TJ = 25°C
VIN = 7V
TJ = 25°C
6.0
DIODE TO OUTPUT
80
DIODE TO INPUT
IOUT = 1A
70
INPUT VOLTAGE (V)
90
EFFICIENCY (%)
EFFICIENCY (%)
90
LT1270
85
LT1271
5.5
DIODE
TO INPUT
5.0
LT1270
80
LT1171
LT1271
4.5
60
0
5
10
15
20
INPUT VOLTAGE (V)
25
4.0
75
30
0
0.5
2.5
1.0
1.5
2.0
LOAD CURRENT (A)
LT1432-3.3 G01
LT1271
6.0
DIODE
TO INPUT
5.0
LT1171
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
TJ = 25°C
5.0
7.0
LT1271
4.5
LT1270
4.0
3.0
1
3
4
2
OUTPUT CURRENT (A)
5
4.5
4.0
3.5
5.0
5
5.5
TJ = 25°C
8.0
3
4
2
OUTPUT CURRENT (A)
Burst Mode Operation Minimum
Input Voltage
5.5
TJ = 25°C
LT1171
1
LT1432-3.3 G03
Minimum Running Voltage –
Normal Mode*
9.0
0
0
LT1432-3.3 G02
Minimum Input Voltage –
Normal Mode (Diode to Output)
4.0
3.0
0
1
3
4
2
OUTPUT CURRENT (A)
3.5
5
0
LT1432-3.3 G05
LT1432-3.3 G04
10
30
40
20
LOAD CURRENT (mA)
50
LT1432-3.3 G06
*SEE MINIMUM INPUT VOLTAGE TO START
Shutdown Current vs Input
Voltage
Current Limit Sense Voltage*
Battery Current in Shutdown*
50
80
40
TJ = 25°C
30
20
SENSE VOLTAGE (mV)
30
CURRENT (µA)
CURRENT (µA)
40
VIN = 30V
20
VIN = 6V
10
70
60
50
10
0
0
5
10
15
20
INPUT VOLTAGE (V)
25
30
0
40
0
25
50
75
100
TEMPERATURE (°C)
LT1432-3.3 G07
LT1432-3.3 G08
*DOES NOT INCLUDE LT1271 SWITCH LEAKAGE.
4
0
50
75
25
JUNCTION TEMPERATURE (°C)
100
LT1432-3.3 G9
* TEMPERATURE COEFFICIENT OF SENSE VOLTAGE IS
DESIGNED TO TRACK COPPER RESISTANCE.
LT1432-3.3
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TYPICAL PERFOR A CE CHARACTERISTICS
No Load Battery Current in Burst
Mode Operation
Incremental Battery Current * in
Burst Mode Operation
2.0
5
5000
TJ = 25°C
1.5
1.0
0.5
Gm =
TRANSCONDUCTANCE (µmho)
BATTERY CURRENT (mA)
INCREMENTAL FACTOR (mA/mA)
TJ = 25°C
4
3
2
1
0
0
5
15
20
10
BATTERY VOLTAGE (V)
0
25
0
5
LT1432-3.3 G10
15
20
10
BATTERY VOLTAGE (V)
* TO CALCULATE TOTAL BATTERY CURRENT IN Burst
Mode OPERATION, MULTIPLY LOAD CURRENT BY
INCREMENTAL FACTOR AND ADD NO-LOAD CURRENT.
25
4000
3000
2000
1000
0
Mode Pin Current
TJ = 25°C
TJ = 25°C
VIN = 7V
TJ = 25°C
Burst Mode OPERATION
–20
40
0
CURRENT (µA)
OUTPUT CHANGE (mV)
0
100
60
25
40
NORMAL MODE
50
75
25
JUNCTION TEMPERATURE (°C)
LT1432-3.3 G12
Burst Mode Operation Load
Regulation
20
∆I(VC PIN)
∆VOUT
LT1432-3.3 G11
Line Regulation
OUTPUT CHANGE (mV)
Transconductance – VOUT to VC
Current
–25
–50
20
0
–20
MODE DRIVE MUST
SINK ≈ 30µA AT 0V
–40
–75
0
10
5
15
20
–40
0
INPUT VOLTAGE (V)
20
60
80
40
LOAD CURRENT (mA)
100
0
2
LT1432-3.3 G14
LT1432-3.3 G13
Restart Load Current
Start-up Switch Characteristics
5
4
TJ = 25°C
VOUT = 4.5V
0
20
10
V+ PIN CURRENT (mA)
3
TIME DELAY (ms)
CURRENT (mA)
30
2
1
0
10
LT1432-3.3 G15
Restart Time Delay
40
0
6
8
4
MODE PIN VOLTAGE (V)
50
75
25
JUNCTION TEMPERATURE (°C)
100
LT1432-3.3 G16
0
NOTE VERTICAL AND
HORIZONTAL SCALE
CHANGES AT 0,0
–20
–40
–60
–80
0
50
75
25
JUNCTION TEMPERATURE (°C)
100
LT1432-3.3 G16
–2
–1
10
0
V + TO VIN VOLTAGE
20
30
LT1432-3.3 G18
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LT1432-3.3
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APPLICATI
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More applications information on the LT1432-3.3 is available
in the LT1432 data sheet.
Basic Circuit Description
The LT1432-3.3 is a dedicated 3.3V buck converter driver
chip intended to be used with an IC switcher from the LT1171/
LT1271 family. This family of current mode switchers includes current ratings from 1.25A to 10A, and switching
frequencies from 40kHz to 100kHz as shown in the table
below.
DEVICE
SWITCH
CURRENT
FREQUENCY
OUTPUT CURRENT IN
BUCK CONVERTER
LT1270A
LT1270
LT1170
LT1070
LT1269
LT1271
LT1171
LT1071
LT1172
LT1072
10A
8A
5A
5A
4A
4A
2.5A
2.5A
1.25A
1.25A
60kHz
60kHz
100kHz
40kHz
100kHz
60kHz
100kHz
40kHz
100kHz
40kHz
7.5A
6A
3.75A
3.75A
3A
3A
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
duty cycles, so these devices are rated at only 80% of their full
current rating when duty cycle is 80%. A second factor is
inductor ripple current, half of which subtracts from maximum available load current. The LT1271 family was originally
intended for topologies which have the negative side of the
switch grounded, such as boost converters. It has an extremely 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
patented adaptive antisat drive that maintains a forced beta of
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
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current limiting, micropower shutdown, and dual mode
operation for high conversion efficiency with both heavy and
very light loads.
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 flowing in the external PCB traces. This is also true for the
frequency compensation capacitor C5. C5 forms the
dominant loop pole.
A floating power supply for the switcher is generated by D2
and C3 which peak detect the input voltage during switch off
time. This is different than the 5V version of the LT1432 which
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
LT1432-3.3
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APPLICATI
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Schottky 1N5818. Diode type is more critical for the output
connection because the high capacitance of Schottky diodes
creates narrow output spikes. These spikes will be eliminated
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
create large spikes, but their high forward resistance requires
even higher input voltage to start.
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
and acceptable output ripple. See the original LT1432 (5V)
data sheet for detailed discussions of these parts.
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
circuit board trace as the sense resistor. The sense voltage
has a positive temperature coefficient of 0.33%/°C to
match the temperature coefficient of copper.
The basic regulator has three different operating modes,
defined by the Mode pin drive. Normal operation occurs when
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.
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 frequency 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.
Some thought must be given to proper sequencing between normal mode and Burst Mode operation. A heavy
(>100mA) load in Burst Mode operation can cause excessive 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 switching 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
Burst Mode Operation
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
operation is used to reduce quiescent operating current when
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 switching 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
LOAD CURRENT – mA (NORMAL MODE)
50
NORMAL MODE
TJ = 25°C
40
30
20
DIODE TO OUTPUT (1N5818)
DIODE TO INPUT (1N5818)
10
0
4
5
7
6
INPUT VOLTAGE (V)
8
9
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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LT1432-3.3
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APPLICATI
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normal mode, then switching to normal mode, pausing for
1ms, followed by return to full load.
If this sequence is not possible, an alternative is to
increase the output capacitor to > 680µF. This modification 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
load current to the lowest possible value (30mA to 500mA),
followed by a short pause and return to full load current.
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PACKAGE DESCRIPTIO
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 overshoot, especially if the output capacitor or frequency
compensation components have been changed.
Dimensions in inches (millimeters) unless otherwise noted.
N8 Package
8-Lead Plastic DIP
0.300 – 0.325
(7.620 – 8.255)
0.009 – 0.015
(0.229 – 0.381)
(
+0.025
0.325 –0.015
8.255
+0.635
–0.381
)
0.400*
(10.160)
MAX
0.130 ± 0.005
(3.302 ± 0.127)
0.045 – 0.065
(1.143 – 1.651)
0.065
(1.651)
TYP
0.125
(3.175)
MIN
0.005
(0.127)
MIN
0.015
(0.380)
MIN
8
7
6
5
1
2
3
4
0.255 ± 0.015*
(6.477 ± 0.381)
0.018 ± 0.003
(0.457 ± 0.076)
0.100 ± 0.010
(2.540 ± 0.254)
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)
8
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
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
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
6
5
0.004 – 0.010
(0.101 – 0.254)
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
7
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
0.050
(1.270)
BSC
SO8 0695
1
2
3
4
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1148
High Efficiency Step-Down Switching Regulator Controller
5V Regulated Output Voltage
LT1432
High Efficiency Synchronous Step-Down Switching Regulator
Adjustable and Fixed 5V or 3.3V Outputs
LT1507
1.5A, 500kHz Step-Down Switching Regulator
Fixed Frequency PWM for Low Input Voltages from 4.5V to 12V
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977
LT/GP 0895 2K REV A • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 1992