LTC3412A Linear Technology, LTC3412A Datasheet - Page 8

• Manufacturer Part Number: LTC3412A
• Description: 3A/ 4MHz/ Monolithic Synchronous Step-Down Regulator
• Manufacturer: Linear Technology

FUNCTIONAL BLOCK DIAGRA
OPERATIO
Main Control Loop
The LTC3412A is a monolithic, constant-frequency, current-
mode step-down DC/DC converter. During normal opera-
tion, the internal top power switch (P-channel MOSFET) is
turned on at the beginning of each clock cycle. Current in
the inductor increases until the current comparator trips
and turns off the top power MOSFET. The peak inductor
current at which the current comparator shuts off the top
power switch is controlled by the voltage on the I
The error amplifi er adjusts the voltage on the I
LTC3412A
8
U
RUN/SS
PGOOD
V
FB
U
4
7
2
U
RUN
0.74V
0.86V
0.8V
SV
+
–
+
–
+
–
1
IN
REFERENCE
VOLTAGE
SYNC/MODE
ERROR
AMPLIFIER
SGND
8
I
TH
+
–
3
TH
W
–
+
OSCILLATOR
TH
pin by
R
pin.
BURST
COMPARATOR
5
T
BCLAMP
comparing the feedback signal from a resistor divider on
the V
current increases, it causes a reduction in the feedback
voltage relative to the reference. The error amplifi er raises
the I
the new load current. When the top power MOSFET shuts
off, the synchronous power switch (N-channel MOSFET)
turns on until either the bottom current limit is reached or
the beginning of the next clock cycle. The bottom current
limit is set at –1.3A for forced continuous mode and 0A
for Burst Mode operation.
COMPENSATION
SYNC/MODE
RECOVERY
SLOPE
LOGIC
TH
FB
6
voltage until the average inductor current matches
pin with an internal 0.8V reference. When the load
COMPARATOR
COMPARATOR
CURRENT
CURRENT
REVERSE
COMPENSATION
NMOS
SLOPE
PMOS CURRENT
COMPARATOR
+
+
–
–
–
+
9
N-CH
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PV
P-CH
IN
16
3412 FBD
10
11
14
15
12
13
SW
PGND
3412afc