Linear Technology DC852A - LTC4354 Negative Voltage Diode-OR Controller and Monitor DC852A DC852A Data Sheet
Product codes
DC852A
LTC4354
5
4354fc
pin FuncTions
DA, DB (Pins 1, 8): Drain Voltage Sense Inputs. These
pins sense source drain voltage drop across the N-channel
MOSFETs. An external resistor is recommended to pro-
tect these pins from transient voltages exceeding 80V in
extreme fault conditions. For Kelvin sensing, connect
these pins as close to the drains as possible. Connect to
V
SS
if unused.
V
CC
(Pin 3): Positive Supply Voltage Input. Connect this
pin to the positive side of the supply through a resistor.
An internal shunt regulator that can sink up to 20mA
typically clamps V
CC
at 11V. Bypass this pin with a 1µF
capacitor to V
SS
.
GA, GB (Pins 4, 6): Gate Drive Outputs. Gate pins pull high
to 10V minimum, fully enhancing the N-channel MOSFET,
when the load current creates more than 30mV of drop
across the MOSFET. When the load current is small,
the gates are actively servoed to maintain a 30mV drop
across the MOSFET. If reverse current develops more than
–140mV of voltage drop across the MOSFET, the pins pull
low to V
SS
in less than 1µs. Quickly turning off the pass
transistors prevents excessive reverse currents. Leave the
pins open if unused.
V
V
SS
(Pins 2, 5): Negative Supply Voltage Input. This is the
device negative supply input and connects to the common
source connection of the N-channel MOSFETs. It also
connects to the source voltage sense input of the servo
amplifiers. For Kelvin sensing, connect Pin 5 as close to
the common source terminal of the MOSFETs as possible.
FAULT (Pin 7): Fault Output. Open-drain output that
FAULT (Pin 7): Fault Output. Open-drain output that
normally pulls the FAULT pin to V
SS
and shunts current
to turn off an external LED or opto-coupler. In the fault
condition, where the pass transistor is fully on and the
voltage drop across it is higher than the fault threshold,
the FAULT pin goes high impedance, turning on the LED or
opto-coupler. This indicates that one or both of the pass
transistors have failed open or failed short creating a cross
conduction current in between the two power supplies.
Connect to V
SS
if unused.
EXPOSED PAD (Pin 9): Exposed pad is common to V
SS
and may be left open or connected to Pins 2 and 5.
FuncTional DiagraM
DB
GB
DA
GA
30mV
BV = 11V
30mV
V
SS
V
CC
V
SS
V
SS
55k
4354 FD
V
SS
FAULT
–
+
–
+
+–
+–
FAULT DETECTION
AMP B
AMP A
5
4
1
6
8
2
7
3
V
SS
55k