LT3501EFE Linear Technology, LT3501EFE Datasheet - Page 9

• Manufacturer Part Number: LT3501EFE
• Description: IC,SMPS CONTROLLER,CURRENT-MODE,BIPOLAR,TSSOP,20PIN,PLASTIC
• Manufacturer: Linear Technology

BLOCK DIAGRAM
The LT3501 is dual channel, constant frequency, current
mode buck converter with internal 3A switches. Each
channel is identical with a common shutdown pin, internal
regulator, oscillator, undervoltage detect, thermal shutdown
and power-on reset.
If the SHDN pin is taken below its 1.28V threshold the
LT3501 will be placed in a low quiescent current mode.
In this mode the LT3501 typically draws 9µA from V
and <1µA from V
with a typical sink capability of 50µA for V
greater than 2V.
R3
V
R
SHDN
GND
IN1
1.28V
T
3µA
/SYNC
+
IN2
+
–
. In shutdown mode the PG is active
7µA
COMPARATOR
SHUTDOWN
REGULATOR
REFERENCE
INTERNAL
AND
UNDERVOLTAGE
Figure 1. Block Diagram (One of Two Switching Regulators Shown)
POR
TSD
COMPARATOR
SOFT-START
S
R Q
RESET
–
+
OSCILLATOR
+
3.25µA
+
AND
AGC
Σ
IN1
80mV
0.8V
SLOPE
COMPENSATION
voltage
LOWEST
VOLTAGE
CLK1
CLK2
IN1
SS
SS CLAMP
C
V
ONE CHANNEL
C
–
+
When the SHDN pin is opened or driven above 1.28V,
the internal bias circuits turn on generating an internal
regulated voltage, 0.8V
and a POR signal which sets the soft-start latch.
As the R
the internal oscillator will start generating two clock signals
180° out of phase for each regulator at a frequency deter-
mined by the resistor from the R
Alternatively, if a synchronization signal is detected by the
LT3501 at the R
CLAMP
T
S
R
/SYNC pin reaches its 0.975V regulation point,
PRE
Q
V
T
C
/SYNC pin, clock signals 180° out of phase
+
ENHANCEMENT
POWER GOOD
COMPARATOR
CIRCUITRY
DROPOUT
DRIVER
0.72V
–
+
+
–
+
–
FB
, 0.975V R
3501 BD
PGOOD
T
V
/SYNC pin to ground.
BST
IND
OUT
SW
V
FB
IN
T
/SYNC references,
LT3501
L1
R1
R2
C
C3
D
3501fb
9
D
C