Datasheet

LTC3850/LTC3850-1
10
38501fc
PIN FUNCTIONS
MODE/PLLIN (Pin 27/Pin 24/Pin 25): Force Continuous
Mode, Burst Mode, or Pulse-Skipping Mode Selection
Pin and External Synchronization Input to Phase Detector
Pin. Connect this pin to SGND to force both channels into
the continuous mode of operation. Connect to INTV
CC
to
enable pulse-skipping mode of operation. Leaving the
pin floating will enable Burst Mode operation. A clock on
the pin will force the controller into continuous mode of
operation and synchronize the internal oscillator.
FREQ/PLLFLTR (Pin 28/Pin 25/Pin 26): The Phase-Locked
Loop’s Low-Pass Filter is Tied to This Pin. Alternatively, this
pin can be driven with a DC voltage to vary the frequency
of the internal oscillator.
Exposed Pad (Pin 29, UF/UFD Packages Only): Signal
Ground. Must be soldered to PCB, providing a local ground
for the control components of the IC, and be tied to the
PGND pin under the IC.
FUNCTIONAL DIAGRAM
4.7V
–
+
–
+
–
+
V
IN
0.5µA
SLOPE COMPENSATION
UVLO
SLOPE RECOVERY
ACTIVE CLAMP
OSC
S
RQ
3k
RUN
SWITCH
LOGIC
AND
ANTI-
SHOOT
THROUGH
BG
ON
FCNT
0.8V
OV
1.2V0.64V
I
TH
R
C
INTV
CC
INTV
CC
I
LIM
I
CMP
C
C1
SS
SGND
R1
0.86V
R2
RUN
PGND
PGOOD
INTV
CC
EXTV
CC
I
REV
SW
TG
C
B
V
IN
C
IN
V
IN
SLEEP
BOOST
BURSTEN
–
+
–
+
UV
OV
C
VCC
V
OUT
C
OUT
M2
M1
L1
D
B
MODE/PLLIN
SENSE
+
SENSE
–
–
+
0.8V
REF
TK/SSRUN
0.55V
–
+
V
FB
FREQ/PLLFLTR
PLL-SYNC
MODE/SYNC
DETECT
+
5V
REG
1.3µA
C
SS
+
–
+
–
+
F
F
0.74V
38501 FD
1
51k
I
THB
–
+
EA
+