LTC3412 LINER [Linear Technology], LTC3412 Datasheet - Page 7

• Manufacturer Part Number: LTC3412
• Description: 2.5A, 4MHz, Monolithic Synchronous Step-Down Regulator
• Manufacturer: LINER [Linear Technology]

OPERATIO
Main Control Loop
The LTC3412 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 amplifier adjusts the voltage on the I
comparing the feedback signal from a resistor divider on
the V
FU CTIO AL BLOCK DIAGRA
U
FB
pin with an internal 0.8V reference. When the load
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
BURST
COMPARATOR
5
pin.
T
BCLAMP
COMPENSATION
current increases, it causes a reduction in the feedback
voltage relative to the reference. The error amplifier 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 –2A for forced continuous mode and 0A for
Burst Mode operation.
The operating frequency is set by an external resistor
connected between the R
switching frequency can range from 300kHz to 4MHz.
SYNC/MODE
RECOVERY
SLOPE
LOGIC
TH
6
voltage until the average inductor current matches
COMPARATOR
COMPARATOR
CURRENT
CURRENT
REVERSE
COMPENSATION
NMOS
SLOPE
PMOS CURRENT
COMPARATOR
+
–
+
–
–
+
T
pin and ground. The practical
N-CH
9
P-CH
PV
IN
16
3412 FBD
LTC3412
10
11
14
15
12
13
SW
PGND
3412fb
7