Datasheet

LTC3104
9
3104f
BLOCK DIAGRAM
–
+
–
+
+
–
+
UVLO
I
PEAK
I
PEAK(REF)
TOP_ON
BOT_ON
V
REF_GOOD
SHUTDOWN
CONTROL
LOGIC
ANTICROSS
CONDUCT
BURST ENABLE
TSD
RUNLDO
V
REF
UVLO
V
CC
OSC
I
BIAS
BOOSTV
CC
V
CC
PRE-REG
+
0.8V
RUN
R6
R5
0.6V 0.8V
–
+
SD LOGIC
RUNLDO
LOGIC
UVLO TSD
SHUTDOWN
LDOENABLE
BST
V
IN
C
BST
V
OUT
L1
V
CC
MODE
THERMAL
SHUTDOWN
PWM
COMP
SLEEP
COMP
SLEEP
REF
GND
0.6V – 10%
PWM
–
+
I
PEAK
COMP
–
+
–
+
I
ZERO
COMP
SLOPE COMP
0.6V
g
m
SS
C3
SW
FB
R2
R1
3104 BD
PGOOD
V
INLDO
V
LDO
FBLDO
C2
C1
R4 C5
V
LDO
R3
LDO
V
CC
LDOENABLE
0.6V
OPERATION
The LTC3104 step-down DC/DC converter is capable of
supplying 300mA to the load. The output voltage is adjust-
able over a broad range and can be set as low as 0.6V.
Both the power and the synchronous rectifier switches
are internal N-channel MOSFETs. The converter uses a
constant-frequency, current mode architecture and may
be configured using automatic Burst Mode operation for
highly efficient light load operation or for low noise forced
continuous conduction operation where the converter is
optimized to operate over a broad range of step-down
ratios without pulse skipping. With the automatic Burst
Mode feature and the LDO enabled, the typical DC supply
current drops to only 2.6µA with no load. The LTC3104
also includes an independent, 10mA LDO regulator with
a V
IN
range of 2.5V to 15V.
Main Control Loop
During normal operation, the internal top power MOSFET
is turned on at the beginning of each cycle and turned
off when the PWM current comparator trips. The peak