NCP4331 datasheet(4/23 Pages) ONSEMI | Synchronous Buck Controller for High Efficiency Post Regulation

4 page

NCP4331

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DETAILED PIN DESCRIPTIONS

Pin Number

Name

Function

CSout

Pin 1 is the output of the auxiliary error amplifier embedded in the NCP4331. This allows for the prevention

of excessive coil or load current. Pin 1 can clamp the main error amplifier output. Controlling the coil

current by this auxiliary error amplifier can provide a CCCV characteristic.

CSin-

Inverting input of the auxiliary error amplifier that is generally used to control the coil current.

CSin+

Noninverting input of the auxiliary error amplifier that is generally used to control the coil current.

UVP/

STDWN

This pin is designed to detect too low input voltage pulses and to turn off both the low-side and high-side

drivers in such a faulty condition. Also, the soft-start pin is grounded so that the circuit smoothly recovers

operation when the detected fault disappears. This UVP detection function features some programmable

hysteresis to avoid erratic turns on and off of the device. Ground Pin 4 to shutdown the part.

COMP

This pin makes available the output of the internal error amplifier, for appropriate compensation of the

regulation loop.

Pin 6 is the feed-back pin that must receive a portion of the output voltage to regulate. It is connected to

the inverting input of the internal error amplifier. The regulation reference is better

$2% over the -40°C to

125

°C temperature range.

Soft-Start/

Dmax

Apply a capacitor to Pin 7 to slow down the start-up phase and reduce the stress during this sequence.

Place a resistor between Pin 7 and ground to adjust the maximum duty-cycle of the high-side MOSFET.

Combine the two functions by implementing these two components in parallel.

Cramp

This pin sources a constant current. Connect a capacitor to create a voltage ramp. This ramp is summed

to the error amplifier output and compared to a constant voltage reference (VPWM) to adjust the

post-regulator duty-cycle.

SYNC

This pin is designed to receive a portion of the input voltage, to synchronize the post-regulator activity to

its pulsed input voltage. Also, the high-side drive cannot be high state if the “SYNC” pin voltage is low.

GND

Ground pin of the circuit.

LS_DRV

”LS_DRV“ is the driver output of the low-side MOSFET gate.

VDD

“VDD” is the circuit power source that is typically provided by the VCC Pin. A 0.1

mF to 1 mF ceramic

capacitor should be connected between this pin and ground for decoupling.

Connect the common node of the two MOSFETs to this pin.

HS_DRV

“HS_DRV” is the driver output of the high-side MOSFET gate.

BST

“BST” is the bootstrap pin. A 0.1

mF to 1 mF ceramic capacitor should be connected between this pin and

the “HB” node. The “BST” voltage feeds the high-side driver (“HS_DRV”).

VCC

A DC voltage (up to 30 V) must be applied to this pin. This voltage is internally post-regulated down to

7.5 V to provide the VDD voltage that powers the circuit.

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