LTC1539_15 Datasheet, PDF (9/32 Pages) Linear Technology – Dual High Efficiency, Low Noise, Synchronous Step-Down Switching Regulators

LTC1538-AUX/LTC1539
PIN FUNCTIONS
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.
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.
W
FUNCTIONAL DIAGRA LTC1539 shown, see specific package pinout for availability of specific functions.
PLLIN**
f_IN
50k
R_LP ^{PLL LPF**}
C_LP
C_OSC
C_OSC
POR1**
BATTERY
SENSE
LBI**
LBO**
2.4V
PHASE
DETECTOR
OSCILLATOR
POWER-ON
RESET
V_FB1
1.11V
DUPLICATE FOR SECOND CONTROLLER CHANNEL
DROPOUT
DETECTOR
SFB
SQ
RQ
0.6V +
–
SHUTDOWN
I1
V_SEC
V_LDO
AUXON
AUXDR
+
9V –
+
–
30k
8k
AUXFB
+
90.8k
+
SFB1*
–
V_IN ^1µA
V_IN
4.8V +
–
EXTV_CC
INTV_CC
+
SGND
10k
SFB
1.19V
REF
V_REF
5V LDO
REGULATOR
INTERNAL
SUPPLY
180k
V_FB
EA
g_m = 1m
OV
3µA
6V
1.28V
1.19V
SHUTDOWN
RUN
SOFT START
V_IN
BOOST
TGL
INTV_CC
D_B
SWITCH
LOGIC
INTV_CC
TGS**
SW
BG
PGND
I2
4k
320k
61k
119k
INTV_CC
SENSE ^–
SENSE ⁺
V_OSENSE*
V_PROG*
C_B
•
+•
C_IN
C_{OUT RSENSE}
V_OUT
C_SEC
D_FB^†
I_TH
C_C
R_C
RUN/SS
C_SS
*NOT AVAILABLE ON BOTH CHANNELS **NOT AVAILABLE ON LTC1538-AUX ^†FOLDBACK CURRENT LIMITING OPTION
BOLD LINES INDICATE HIGH CURRENT PATHS
1438 FD
9