LTC3850_15 Datasheet, PDF (10/38 Pages) Linear Technology – Dual, 2-Phase Synchronous Step-Down Switching Controller

LTC3850/LTC3850-1
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
FREQ/PLLFLTR MODE/PLLIN
PLL-SYNC
MODE/SYNC
DETECT
EXTV_CC
4.7V
–+
F
0.8V
5V
REG
–+
F
OSC
3k
I_CMP
S
RQ
–
I_REV
+
FCNT
BURSTEN
ON
SWITCH
LOGIC
AND
ANTI-
SHOOT
THROUGH
RUN
OV
I_LIM
SLOPE COMPENSATION
INTV_CC
UVLO
V_IN
V_IN
+
C_IN
INTV_CC
BOOST
TG
C_B
SW
SENSE⁺ DB
SENSE^–
BG
C_VCC
PGND
PGOOD
INTV_CC
M1
L1
V_OUT
+
C_OUT
M2
1
SLOPE RECOVERY
51k
ACTIVE CLAMP
I_THB
0.74V
UV
R2
V_FB
V_IN
SLEEP
0.8V
REF
EA
–+
0.55V
– ^SS +
0.64V
– ^RUN +
1.2V
OV
1.3µA
R1
0.86V
SGND
0.5µA
I_{TH RC} ^CC1
RUN
TK/SS
C_SS
38501 FD
10
38501fc