LTC1874 Linear Technology, LTC1874 Datasheet - Page 4

• Manufacturer Part Number: LTC1874
• Description: Dual Constant Frequency Current Mode Step-Down DC/DC Controller
• Manufacturer: Linear Technology

LTC1874
PIN
V
delivers the Input DC Supply Current (listed in the Electri-
cal Characteristics table) plus a small amount of logic
switching current. Must be connected to PV
and closely decoupled to GND1 (Pin 3).
SENSE1
Comparator of Controller #1.
GND1 (Pin 3): Signal Ground for Controller #1. Must be
connected to PGND1 (Pin 14).
V
external resistive divider across the output of Controller
#1.
I
serves as the error amplifier compensation point as well as
the run control input of Controller #2. The current com-
parator threshold increases with this control voltage.
Nominal voltage range for this pin is 0.7V to 1.9V. Forcing
this pin below 0.35V causes Controller #2 to be shut down.
In shutdown, all functions of Controller #2 are disabled
and PGATE2 (Pin 7) is held high.
PGND2 (Pin 6): Power Ground for Controller #2. Must be
connected to GND2 (Pin 11).
PGATE2 (Pin 7): Gate Drive for the External P-Channel
MOSFET of Controller #2. This pin swings from 0V to the
voltage of PV
PV
delivers the dynamic switching current that drives the gate
of the external P-channel MOSFET of Controller #2. Must
be connected to V
PGND2 (Pin 6).
4
TH
IN1
FB1
IN2
/RUN2 (Pin 5): This pin performs two functions. It
U
(Pin 1): Main Supply Pin for Controller #1. This pin
(Pin 4): Receives the feedback voltage from an
(Pin 8): Power Supply Pin for Controller #2. This pin
FUNCTIONS
–
(Pin 2): The Negative Input to the Current
U
IN2
.
IN2
U
(Pin 9) and closely decoupled to
IN1
(Pin 16)
V
delivers the Input DC Supply Current (listed in the Electri-
cal Characteristics table) plus a small amount of logic
switching current. Must be connected to PV
closely decoupled to GND2 (Pin 11).
SENSE2
Comparator of Controller #2.
GND2 (Pin 11): Signal Ground for Controller #2. Must be
connected to PGND2 (Pin 6).
V
external resistive divider across the output of Controller
#2.
I
serves as the error amplifier compensation point as well as
the run control input of Controller #1. The current com-
parator threshold increases with this control voltage.
Nominal voltage range for this pin is 0.7V to 1.9V. Forcing
this pin below 0.35V causes Controller #1 to be shut down.
In shutdown, all functions of Controller #1 are disabled
and PGATE1 (Pin 15) is held high.
PGND1 (Pin 14): Power Ground for Controller #1. Must be
connected to GND1 (Pin 3).
PGATE1 (Pin 15): Gate Drive for the External P-Channel
MOSFET of Controller #1. This pin swings from 0V to the
voltage of PV
PV
pin delivers the dynamic switching current that drives the
gate of the external P-channel MOSFET of Controller #1.
Must be connected to V
to PGND1 (Pin 14).
TH
IN2
FB2
IN1
/RUN1 (Pin 13): This pin performs two functions. It
(Pin 9): Main Supply Pin for Controller #2. This pin
(Pin 12): Receives the feedback voltage from an
(Pin 16): Power Supply Pin for Controller #1. This
–
(Pin 10): The Negative Input to the Current
IN1
.
IN1
(Pin 1) and closely decoupled
IN2
(Pin 8) and