LT3992 Datasheet, PDF (1/36 Pages) –

LT3992
Monolithic Dual Tracking
3A Step-Down Switching Regulator
Features
n _{Wide Input Range:}
– Operation from 3V to 60V
n _{Independent Supply, Shutdown, Soft-Start, UVLO,}
Programmable Current Limit and Programmable
Power Good for Each 3A Regulator
n _{Die Temperature Monitor}
n _{Adjustable/Synchronizable Fixed Frequency}
Operation from 250kHz to 2MHz with Synchronized
Clock Output
n _{Independent Synchronized Switching Frequencies}
Optimize Component Size
n _{Antiphase Switching}
n _{Outputs Can Be Paralleled}
n _{Flexible Output Voltage Tracking}
n _{Low Dropout: 95% Maximum Duty Cycle}
n _{5mm × 5mm QFN Package}
n _{FMEA Compliant 38-Pin Exposed Pad TSSOP Package}
Applications
n _{Automotive Supplies}
n _{Distributed Supply Regulation}
Description
The LT^®3992 is a dual current mode PWM step-down
DC/DC converter with two internal 4.6A switches. Inde-
pendent input voltage, shutdown, feedback, soft-start,
UVLO current limit and comparator pins for each channel
simplify complex power supply tracking and sequencing
requirements.
To optimize efficiency and component size, both convert-
ers have a programmable maximum current limit and are
synchronized to either a common external clock input, or
a resistor settable fixed 250kHz to 2MHz internal oscillator.
A frequency divider is provided for channel 1 to further
optimize component size. At all frequencies, a 180° phase
relationship between channels is maintained, reducing volt-
age ripple and component size. A clock output is available
for synchronizing multiple regulators.
Minimum input to output voltage ratios are improved by
allowing the switch to stay on through multiple clock cycles
only switching off when the boost capacitor needs recharg-
ing. Independent channel operation can be programmed
using the SHDN pin. Disabling both converters reduces
the total quiescent current to <10µA.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
Typical Application
12V and 5V 2-Stage Multi-Frequency Step-Down Converter
V_IN1
15V TO 60V
4.7µF
V_OUT1
12V
1A
400kHz
PG
V_OUT2
V_IN1
SHDN1
V_IN2
SHDN2
100k
0.1µF
22µF _8.06k
22µH
113k
BST1
SW1
BST2
SW2
IND1
IND2
LT3992
V_OUT1
V_OUT2
FB1
CMPI1
FB2
CMPI2
CMPO1 CMPO2
0.1µF
100k
33pF
680pF
15k
48.7k
SS1
SS2
ILIM1
V_C1
ILIM2
V_C2
RT/SYNC CLKOUT
DIV
GND
T_J
102k
2.2µH
0.1µF
42.2k _8.06k
FB1
CLKOUT
1600kHz
10nF
33pF
680pF
10k
47µF
V_OUT2
5V
2A
1600kHz
0.1µF
60.4k
3992 TA01a
Independent Synchronized
Switching Frequencies Extend
Full Frequency Input Range
V_IN = 60V
500ns/DIV
CH1
400kHz
20V/DIV
CH2
1.6MHz
5V/DIV
3992 TA01b
3992f
1