LTC1439 Linear Technology, LTC1439 Datasheet - Page 9

• Manufacturer Part Number: LTC1439
• Description: Dual High Efficiency/ Low Noise/ Synchronous Step-Down Switching Regulators
• Manufacturer: Linear Technology

FUNCTIONAL DIAGRA
PIN
12V operation. When used as a comparator, this is the
noninverting input of a comparator whose inverting input
is tied to the internal 1.19V reference. See Auxiliary Regu-
lator Application section.
AUXON: Pulling this pin high turns on the auxiliary regu-
lator/comparator. The threshold is 1.19V. This is a conve-
nient linear power supply logic-controlled on/off input.
BATTERY
V
V
SEC
LDO
SENSE
C
C
OSC
U
LP
U
+
*IN SOME VERSIONS, NOT AVAILABLE ON BOTH CHANNELS
V
+
IN
FUNCTIONS
f
R
IN
LP
AUXON**
AUXDR**
AUXFB**
PLL LPF**
EXTV
INTV
PLLIN**
SGND
POR2
U
C
SFB1*
LBO
LBI
V
OSC
IN
CC
CC
U
50k
1 A
4.8V
+
–
OSCILLATOR
POWER-ON
DETECTOR
U
90.8k
PHASE
RESET
+
–
2.4V
–
+
–
+
9V
V
1.11V
SFB
FB2
+
–
10k
REGULATOR
INTERNAL
SUPPLY
5V LDO
1.19V
W
REF
**NOT AVAILABLE ON LTC1438
V
REF
DUPLICATE FOR SECOND CONTROLLER CHANNEL
6V
3 A
S
R
0.6V
†
Q
Q
FOLDBACK CURRENT LIMITING OPTION
180k
DETECTOR
g
DROPOUT
SHUTDOWN
m
–
–
+
+
= 1m
0V
1.28V
1.19V
30k
AUXDR: Open Drain Output of the Auxiliary Regulator/
Comparator. The base of an external PNP device is con-
nected to this pin when used as a linear regulator. An
external pull-up resistor is required for use as a compara-
tor. A voltage > 9.5V on AUXDR causes the internal 12V
resistive divider to be connected in series with the AUXFB pin.
I1
SOFT START
+
–
EA
–
+
RUN
SHUTDOWN
+
–
8k
V
SFB
FB
SWITCH
LOGIC
BOLD LINES INDICATE HIGH CURRENT PATHS
61k
119k
320k
I2
4k
INTV
LTC1438/LTC1439
–
+
CC
INTV
CC
V
SENSE
SENSE
V
RUN/SS
BOOST
OSENSE
PGND
PROG
TGS**
TGL
SW
I
BG
TH
*
–
+
*
V
C
IN
C
D
C
OUT
FB
†
C
+
V
SS
R
+
OUT
C
R
SENSE
INTV
C
IN
•
CC
D
C
C
B
SEC
9
B
+
1438 FD
•