6
LTC1143/LTC1143L
LTC1143L-ADJ
PIN FUNCTIONS
UUU
V
IN3
(Pin 13): Supply Pin, 3.3V Section. Must be closely
decoupled to 3.3V power ground Pin 3.
C
T3
(Pin 14): External capacitor C
T3
from Pin 14 to ground
sets the operating frequency for the 3.3V section. (The
actual frequency is also dependent upon the input voltage.)
I
TH3
(Pin 15): Gain Amplifier Decoupling Point, 3.3V
Section. The 3.3V section current comparator threshold
increases with the Pin 15 voltage.
SENSE
–
3 (Pin 16): Connects to internal resistive
divider which sets the output voltage for the 3.3V
section. Pin 16 is also the (–) input for the current
comparator on the 3.3V section.
LTC1143L-ADJ
SENSE
+
1 (Pin 1): The (+) Input to the Section 1 Current
Comparator. A built-in offset between Pins 1 and 16 in
conjunction with R
SENSE 1
sets the current trip threshold
for section 1.
V
FB1
(Pin 2): This pin serves as the feedback pin from an
external resistive divider used to set the output voltage for
section 1.
GND1 (Pin 3): Section 1 Ground. Two independent ground
lines must be routed separately from other grounds to: 1)
the (–) terminal of the section 1 output capacitor and 2) the
cathode of the Schottky diode D1 and (–) terminal of C
IN1
(see Figure 1).
P-DRIVE 1 (Pin 4): High Current Drive for Top P-Channel
MOSFET, Section 1. Voltage swing at this pin is from V
IN1
to ground.
V
IN2
(Pin 5): Supply Pin, Section 2. Must be closely
decoupled to power ground Pin 11.
C
T2
(Pin 6): External capacitor C
T2
from Pin 6 to ground sets
the operating frequency for section 2. (The actual frequency
is also dependent upon the input voltage.)
I
TH2
(Pin 7): Gain Amplifier Decoupling Point, Section 2.
The section 2 current comparator threshold increases
with the Pin 7 voltage.
SENSE
–
2 (Pin 8): Pin 8 is the (–) input for the current
comparator on section 2.
SENSE
+
2 (Pin 9): The (+) Input to the Section 2 Current
Comparator. A built-in offset between Pins 9 and 8 in
conjunction with R
SENSE 2
sets the current trip threshold
for section 2.
V
FB2
(Pin 10): This pin serves as the feedback pin from an
external resistive divider used to set the output voltage for
section 2.
GND2 (Pin 11): Section 2 Ground. Two independent
ground lines must be routed separately from other grounds
to: 1) the (–) terminal of section 2 output capacitor and 2)
the cathode of the Schottky diode D2 and (–) terminal of
C
IN2
(see Figure 1).
P-DRIVE 2 (Pin 12): High Current Drive for Top P-Channel
MOSFET, Section 2. Voltage swing at this pin is from V
IN2
to ground.
V
IN1
(Pin 13): Supply Pin, Section 1. Must be closely
decoupled to power ground Pin 3.
C
T1
(Pin 14): External capacitor C
T1
from Pin 14 to ground
sets the operating frequency for section 1. (The actual
frequency is also dependent upon the input voltage.)
I
TH1
(Pin 15): Gain Amplifier Decoupling Point, Section 1.
The section 1 current comparator threshold increases
with the Pin 15 voltage.
SENSE
–
1 (Pin 16): Pin 16 is the (–) input for the
current comparator on section 1.
