Datasheet

LTC3416
6
3416fa
FU CTIO AL DIAGRA
U
U
W
–
+
–
+
–
+
–
+
19
ERROR
AMPLIFIER
0.74V
V
FB
3
TRACK
SV
IN
4
RUN/SS
17
PGOOD
RUN
0.86V
–
+
VOLTAGE
REFERENCE
SLOPE
COMPENSATION
OSCILLATOR
R
T
LOGIC
SLOPE
COMPENSATION
RECOVERY
PMOS CURRENT
COMPARATOR
NMOS CURRENT
COMPARATOR
16
SGND
5
EXPOSED
PAD
21
I
TH
18
SW
PGND
3416 FD
8
PV
IN
7 14
9
12
13
1
10
11
202
OPERATIO
U
Main Control Loop
The LTC3416 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
TH
pin.
The error amplifier adjusts the voltage on the I
TH
pin by
comparing the feedback signal from a resistor divider on
the V
FB
pin with an internal 0.8V reference. When the load
current increases, it causes a reduction in the feedback
voltage relative to the reference. The error amplifier raises
the I
TH
voltage until the average inductor current matches
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 –5A.
The operating frequency is externally set by an external
resistor connected between the R
T
pin and ground. The
practical switching frequency can range from 300kHz to
4MHz.
Overvoltage and undervoltage comparators will pull the
PGOOD output low if the output voltage comes out of
regulation by ±7.5%. In an overvoltage condition, the top