ltc4350 Linear Technology Corporation, ltc4350 Datasheet - Page 5

• Manufacturer Part Number: ltc4350
• Description: Hot Swappable Load Share Controller
• Manufacturer: Linear Technology Corporation

PI FU CTIO S
COMP2 (Pin 5): Analog Output Pin. This pin is the output
of the share bus error amplifier E/A2. (A compensation
capacitor between this pin and ground sets the crossover
frequency for the power supply adjustment loop.) In most
cases, this pin operates between 0.5V to 1.5V and repre-
sents a diode voltage up from the voltage at the R
It is clamped at 3V. During start-up, this pin is clamped to
ground. After a timer cycle (and if the GATE pin is high), the
COMP2 pin is released.
COMP1 (Pin 6): Analog Output Pin. This pin is the output
of the voltage regulating error amplifier E/A1. A compen-
sation capacitor between this pin and ground sets the
crossover frequency of the share bus loop. This pin
operates a diode voltage up from the voltage at the SB pin
and is clamped at 8.4V.
SB (Pin 7): Analog Output Pin. This pin drives the share
bus used to communicate the value of shared load current
between several power supplies. There is an amplifier that
drives this pin a diode below the COMP1 pin using an
internal NPN as a pull-up and a 20k resistor as a pull-down.
GND (Pin 8): Chip Ground.
FB (Pin 9): Analog Error Amplifier Input (E/A1). This pin is
used to monitor the output supply voltage with an external
resistive divider. The FB pin voltage is compared to 1.220V
reference. The difference between the FB pin voltage and
the reference is amplified and output on the COMP1 pin.
R
converts the voltage at the COMP2 pin (down a diode
voltage) to the R
external resistor (R
ground is (COMP2 – V
adjust the output voltage.
I
the I
pin that was set by the external resistor R
is used to adjust the output supply voltage by modifying
the voltage sensed by the power supply’s internal voltage
feedback circuitry.
OUT
SET
U
OUT
(Pin 11): Analog Output Pin. The current flowing into
(Pin 10): Analog Output Pin. The I
pin is equal to the current flowing out of the R
U
SET
SET
pin. Therefore, the current through the
U
DIODE
) placed between the R
)/R
SET
. This current is used to
SET
OUT
. This current
SET
amplifier
SET
pin and
pin.
SET
R
in the supply path between the R
supply current is measured as a voltage drop between R
and R
multiplied at the GAIN pin.
R
in the supply path between the R
supply current is measured as a voltage drop between R
and R
multiplied at the GAIN pin.
GATE (Pin14): The high side gate drive for the external
N-Channel power FET. An internal charge pump provides
the gate drive necessary to drive the FETs. The slope of the
voltage rise or fall at the GATE is set by an external
capacitor connected between GATE and GND, and the
10µA charge pump output current. When the undervoltage
lockout circuit monitoring V
high or the UV pin is pulled low, the GATE pin is immedi-
ately pulled to GND.
STATUS (Pin 15): Open-Drain Digital Output. The STA-
TUS pin has an open-drain output to GND. This pin is
pulled low to indicate a fault has occurred in the system.
There are three types of faults. The first is a undervoltage
lockout on V
voltage is active. The second is when the COMP2 pin is
above 1.5V or below 0.5V and the voltage on the GAIN pin
is greater than 100mV. The final failure is when the OV pin
is high. The three faults will activate the pull-down on the
STATUS pin after a timing cycle.
V
3.3V to 12V for Normal Operation. I
An undervoltage lockout circuit disables the chip until the
voltage at V
capacitor is required on the V
to the same power supply output that is being adjusted,
then a 51Ω decoupling resistor is needed to hold up the
supply during a short to ground on the supply output. V
must be greater than or equal to the supply that is
connected to the R
CC
–
+
(Pin 12): Analog Input Pin. With a sense resistor placed
(Pin 13): Analog Input Pin. With a sense resistor placed
(Pin 16): The Positive Supply Input, Ranging from
–
–
. This voltage is measured by the I
. This voltage is measured by the I
CC
CC
is greater than 2.47V. A 0.1µF bypass
or the UV pin is low while the output
+
and R
–
CC
pins.
CC
trips, the OV pin is pulled
+
+
pin. If the V
and R
and R
CC
is typically 1.6mA.
–
–
SENSE
SENSE
LTC4350
pins, the power
pins, the power
CC
pin is tied
block and
block and
4350fa
5
CC
+
+