Datasheet
LT3692
10
3692fa
For more information www.linear.com/3692
block DiagraM
Figure 1. LT3692 Block Diagram
The LT3692 is a dual channel, constant frequency, current
mode buck converter with internal 3.5A switches. Each
channel can be independently controlled with the exception
that V
IN1
must be above the 2.8V undervoltage lockout
threshold to power the common internal regulator, oscil-
lator and thermometer circuitry.
If the SHDN1 pin is taken below its 1.3V threshold switch-
ing on both channels will be disabled. Further reducing the
SHDN1 below a typical value of 0.6V will place the L
T3692
in a low quiescent current mode. In this mode the L
T3692
typically draws 6µA from V
IN1
and <1µA from V
IN2
. When
the SHDN pin is driven above 1.3V, the internal bias circuits
turn on generating an internal regulated voltage, 0.806V
FB
,
12µA RT/SYNC, DIV and ILIM current references, and a
POR signal which sets the soft-start latch.
Once the internal reference reaches its regulation point,
the internal oscillator will start generating a master clock
signal for the two regulators at a frequency determined
by the voltage present at the RT/SYNC pin. The channel 1
clock is then divided by 1, 2, 4 or 8 depending on the
voltage present at the DIV pin. Channel 2’s clock runs at
the master clock frequency with a 180° phase shift from
channel 1.
Alternatively, if a synchronization signal is detected by
the LT3692 the RT/SYNC pin, the master clock will be
generated at the incoming frequency on the rising edge
of the synchronization pulse with channel 1 in phase with
the synchronization signal. Frequency division and phase
remains the same as the internally generated master clock.
2.8V
3692 F01
+
–
V
IN1
+
–
+
–
+
–
+
+
–
1.3V
38V
THERMAL
SHUTDOWN
V
IN1
SHDN1
SS1
V
C1
90mV
+
–
12µA
2.5V
12µA
2.5V
ILIM1
R
LIM
PRE
SLOPE
COMPENSATION
DRIVER
CIRCUITRY
DROPOUT
ENHANCEMENT
CHANNEL 1
OSCILLATOR
AND AGC
INTERNAL
REGULATOR
AND
REFERENCES
CLK2 TO CHANNEL 2
MASTER CLOCK
CLK1
0.806V
2.5V
0.72V
S Q
R
+
–
PRE
S
Q
R
12µA
2.5V
RT/SYNC
12µA
2.5V
DIV
R3
R
DIV
BST1
SW1
IND1
FB1
R1
R2
CMPI1
CMPO1
T
J
CLKOUT
GND
V
OUT1
V
IN1
+
–
applicaTions inForMaTion