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Linear Technology Electronic Components Datasheet

LT1432 Datasheet

5V High Efficiency Step-Down Switching Regulator Controller

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LT1432
5V High Efficiency Step-Down
Switching Regulator Controller
FEATURES
s Accurate Preset +5V Output
s Up to 90% Efficiency
s Optional Burst Mode for Light Loads
s Can be Used with Many LTC Switching ICs
s Accurate Ultra-Low-Loss Current Limit
s Operates with Inputs from 6V to 30V
s Shutdown Mode Draws Only 15µA
s Uses Small 50µH Inductor
APPLICATI S
s Laptop and Palmtop Computers
s Portable Data-Gathering Instruments
s DC Bus Distribution Systems
s Battery-Powered Digital Widgets
DESCRIPTIO
The LT1432 is a control chip designed to operate with the
LT1170/LT1270 family of switching regulators to make a
very high efficiency 5V step-down (buck) switching regula-
tor. 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 6V input.
The LT1432 has a logic controlled “burst” mode to achieve
high efficiency at very light load currents (0 to 100mA) such
as memory keep-alive. In normal switching mode, the
standby power loss is about 60mW, limiting efficiency at
light loads. In burst mode, standby loss is reduced to
approximately 15mW. Output current in this mode is
typically in the 5mA to 100mA range.
The LT1432 is available in 8-pin surface mount and DIP
packages. The LT1170/LT1270 family will also be available
in a surface mount version of the 5-pin TO-220 package.
For 3.3V versions contact Linear Technology Corporation.
TYPICAL APPLICATI
VIN
+
C1
330µF
35V
VSW VIN
LT1170
LT1271
FB
VC GND
C6
0.02µF
C4
0.1µF
R1
680
C5
0.03µF
C3 +
4.7µF
TANT
D1
MBR330p
VC DIODE
D2
1N4148
10µH
3A
+
100µF
16V
OPTIONAL
OUTPUT
FILTER
L1
50µH
V+
R2*
0.013
+
× VOUT
5V
C2 3A**
390µF
16V
VIN VLIM
LT1432
MODE LOGIC
220pF
<0.3V = NORMAL MODE
>2.5V = SHUTDOWN
OPEN = BURST MODE
MODE
VOUT
GND * R2 IS MADE FROM PC BOARD
COPPER TRACES.
** MAXIMUM CURRENT IS DETERMINED
BY THE CHOICE OF LT1070 FAMILY.
SEE APPLICATION SECTION.
LT1432 TA01
Figure 1. High Efficiency 5V Buck Converter
100
90
80
70
60
0
0
Efficiency
NORMAL MODE
(USE AMPS SCALE)
BURST MODE
(USE mA SCALE)
1A
20mA
LT1271, L = 50µH
2A
40mA
3A
60mA
LT1432 TA02
1


Linear Technology Electronic Components Datasheet

LT1432 Datasheet

5V High Efficiency Step-Down Switching Regulator Controller

No Preview Available !

LT1432
ABSOLUTE AXI U RATI GS
VVI+NPPinin.........................................................................................................................................
30V
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
PACKAGE/ORDER I FOR ATIO
TOP VIEW
VLIM 1
VOUT 2
VIN 3
V+ 4
8 MODE
7 GND
6 VC
5 DIODE
N8 PACKAGE
8-LEAD PLASTIC DIP
S8 PACKAGE
8-LEAD PLASTIC SO
ORDER PART
NUMBER
LT1432CN8
LT1432CS8
ELECTRICAL CHARACTERISTICS
VC = 6V, VIN = 12V, V+ = 10V, VDIODE = Open, VLIM = VOUT, VMODE = 0V, TJ = 25°C
Device is in standard test loop unless otherwise noted.
PARAMETER
CONDITIONS
MIN TYP MAX
UNITS
Regulated Output Voltage
Output Voltage Line Regulation
Input Supply Current (Note 1)
Quiescent Output Load Current
VC Current = 220µA
VIN = 6V to 30V
VIN = 6V to 30V, V+ = VIN + 5V, VC = VIN + 1V
q
q
q
4.9 5.0 5.1
5 20
0.3 0.5
0.9 1.2
V
mV
mA
mA
Mode Pin Current
Mode Pin Threshold Voltage
(Normal to Burst)
VMODE = 0V (current is out of pin)
VMODE = 5V (shutdown)
IMODE = 10µA (out of pin)
q 30 50
q 15 30
q 0.6 0.9 1.5
µA
µA
V
VC Pin Saturation Voltage
VC Pin Maximum Sink Current
VC Pin Source Current
Current Limit Sense Voltage (Note 3)
VOUT = 5.5V (forced)
VOUT = 5.5V (forced)
VOUT = 4.5V (forced)
Device in Current Limit Loop
q 0.25 0.45
q
0.45 0.8
1.5
q 40 60 100
56 60 64
V
mA
µA
mV
VLIM Pin Current
Supply Current in Shutdown
Burst Mode Output Ripple
Burst Mode Average Output Voltage
Device in Current Limit Loop
(current is out of pin)
VMODE > 3V, VIN < 30V, VC and V+ = 0V
Device in Burst Test Circuit
Device in Burst Test Circuit
q 30 45 70
q 15 60
100
q 4.8 5 5.2
µA
µA
mVp-p
V
Clamp Diode Forward Voltage
Startup Drive Current
Restart Time Delay
IF = 1mA, All Other Pins Open
VOUT
VIN =
= 2.5V (forced),
6V to 26V, V+ =
V+ = 5V to 25V,
VIN – 1V, VC = VIN
1.5V
(Note 4)
q
q
0.5 0.65
30 45
1 1.8 10
V
mA
ms
Transconductance, Output to VC Pin
IC = 150µA to 250µA
q 1500 2000 2800
µmho
The q denotes specifications which apply over the operating temperature
range.
Note 1: Does not include current drawn by the LT1070 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.
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 5.5Vto 4.5V.
2


Part Number LT1432
Description 5V High Efficiency Step-Down Switching Regulator Controller
Maker Linear Technology
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LT1432 Datasheet PDF






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