LTC3407-4 Linear Technology, LTC3407-4 Datasheet - Page 6

• Manufacturer Part Number: LTC3407-4
• Description: Dual Synchronous 800mA 2.25MHz Step-Down DC/DC Regulator
• Manufacturer: Linear Technology

BLOCK DIAGRA
OPERATIO
LTC3407-4
6
The LTC3407-4 uses a constant frequency, current mode
architecture. The operating frequency is set at 2.25MHz
and can be synchronized to an external oscillator. Both
channels share the same clock and run in-phase. To suit
a variety of applications, the selectable Mode pin allows
the user to choose between low noise and high efficiency.
The output voltage is set by an external divider returned to
the V
output voltage with a reference voltage of 0.6V and adjusts
the peak inductor current accordingly. Overvoltage and
undervoltage comparators will pull the POR output low if
the output voltage is not within ±8.5%. The POR output
will go high after 2
skipping mode) of achieving regulation.
FB
pins. An error amplfier compares the divided
MODE/SYNC
RUN1
RUN2
V
V
FB1
FB2
U
10
16
6
1
2
9
clock cycles (about 29ms in pulse
REGULATOR 1
0.6V REF
REGULATOR 2 (IDENTICAL TO REGULATOR 1)
0.55V
0.65V
W
0.6V
SHUTDOWN
+
–
–
+
+
–
UVDET
OVDET
OSC
EA
I
UV
OV
TH
OSC
0.35V
SLOPE
COMP
S
R
LATCH
–
+
RS
BURST
Q
Q
EN
Main Control Loop
During normal operation, the top power switch (P-channel
MOSFET) is turned on at the beginning of a clock cycle
when the V
The current into the inductor and the load increases until
the current limit is reached. The switch turns off and
energy stored in the inductor flows through the bottom
switch (N-channel MOSFET) into the load until the next
clock cycle.
The peak inductor current is controlled by the internally
compensated I
amplifier.This amplifier compares the V
reference. When the load current increases, the V
age decreases slightly below the reference. This
SWITCHING
BLANKING
COUNTER
CIRCUIT
SLEEP
LOGIC
POR
AND
PGOOD1
PGOOD2
–
FB
I
COMP
SHOOT-
THRU
I
ANTI
RCMP
voltage is below the the reference voltage.
TH
+
+
–
BURST
CLAMP
voltage, which is the output of the error
5Ω
www.DataSheet4U.com
V
V
IN
IN
11
4
FB
3
8
5
7
SW1
GND
V
POR
GND
SW2
pin to the 0.6V
IN
FB
volt-
34074f