LT3641_15 Datasheet, PDF (1/28 Pages) Linear Technology – Dual Monolithic Buck Regulator with Power-On Reset and Watchdog Timer

LT3641
Dual Monolithic Buck
Regulator with Power-On
Reset and Watchdog Timer
FEATURES
DESCRIPTION
n _{High Voltage Buck Regulator:}
4V to 42V Operating Range
1.3A Output Current
n _{Input Transient Protection to 55V}
n _{Low Voltage Synchronous Buck Regulator:}
2.5V to 5.5V Input Voltage Range
1.1A Output Current
n _{Synchronizable, Adjustable 350kHz to 2.5MHz}
Switching Frequency
n _{Programmable Power-On Reset Timer}
n _{Programmable Window Mode Watchdog Timer}
n _{Typical Quiescent Current: 290μA}
n _{Short-Circuit Robust}
n _{Programmable Soft-Start}
n _{Low Shutdown Current: IQ < 1μA}
n _{Thermal Shutdown}
n _{Available in Thermally Enhanced 28-Lead}
(4mm × 5mm) QFN and 28-Lead TSSOP Packages
APPLICATIONS
n _{Industrial Power Supplies}
n _{Automotive Electronic Control Units}
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
The LT^®3641 is a dual channel, current mode monolithic buck
switching regulator with a power-on reset and a watchdog
timer. Both regulators are synchronized to a single oscillator
with an adjustable frequency (350kHz to 2.5MHz). At light
loads, both regulators operate in low ripple Burst Mode^®
to maintain high efficiency and low output ripple.
The high voltage channel is a nonsynchronous buck with
an internal 2.4A top switch that operates from an input
of 4V to 42V and input transient protection to 55V. The
low voltage channel operates from an input of 2.5V to
5.5V. Internal synchronous power switches provide high
efficiency without the need of external Schottky diode.
Both channels have cycle-by-cycle current limit, providing
protection against shorted outputs.
The power-on reset and watchdog timeout periods are
both adjustable using external capacitors. The window
mode watchdog timer flags when the μP pulses group
too close together or too far apart.
The LT3641 is available in a 28-pin 4mm × 5mm QFN
package and 28-pin TSSOP package. Both packages have
an exposed pad for low thermal resistance.
TYPICAL APPLICATION
2MHz 5V/0.8A and 3.3V/0.5A Step Down Regulators
V_IN
7V TO 42V*
V_OUT1
100k
μP
0.22μF
10μF
EN/UVLO V_IN SW
SYNC
WDE
PGOOD2
BST SW1
DA
FB1
100k
RST1
LT3641
V_IN2
RST2
WDO
EN2
WDI
SW2
1.5nF
CWDT
FB2
CPOR RT GND SS2 SS1
1.5nF
32.4k
1nF
1nF
4.7μH
301k
100k
2.2μH
226k
49.9k
3641 TA01a
V_OUT1
5V/0.8A
22μF
V_OUT2
3.3V/0.5A
22μF
* FOR INPUT VOLTAGES ABOVE 42V RESTRICTIONS APPLY
HV Channel Efficiency,
2MHz, V_OUT1 = 5V
90
V_IN = 12V
85
80
75
70
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4
V_OUT1 CURRENT (A)
3641 TA01b
LV Channel Efficiency,
2MHz, V_OUT2 = 3.3V
95
90
V_IN2 = 5V
85
80
75
70
0
0.2 0.4 0.6 0.8 1.0 1.2
V_OUT2 CURRENT (A)
3641 TA01c
3641fa
1