ncv8881 ON Semiconductor, ncv8881 Datasheet - Page 4

• Manufacturer Part Number: ncv8881
• Description: Ncv8881 1.5a Automotive Buck Regulator With Watchdog
• Manufacturer: ON Semiconductor

PIN FUNCTION DESCRIPTIONS
Pin No.
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
EXPOSED
LDOMON
IGNBUF
Symbol
COMP
SYNC
ROSC
RESB
RDLY
GND
WDI
BST
PAD
8P5
5P0
SW
VIN
EN
FB
This open drain output is pulled low whenever the EN signal is latched and a low level is recognized at
the EN input.
CMOS compatible Watchdog pulse input from a CPU. To be valid, the time between falling edges of this
signal must be less than the programmed Watchdog Delay.
Delay programming pin for POR, BOOT and Watchdog delays. Connect a resistor between this pin and
ground.
This is an open drain output for resetting a CPU. RESB goes low if the WDI signal period is longer than
the programmed Watchdog delay, if VIN is above or below operating voltage, if the SMPS output is out of
regulation, or if the part is in thermal shutdown.
Logic compatible Enable input. Once a high is received at the EN pin, the part enters a startup
sequence. Until expiration of the Soft−Start Timer, a low at the EN pin will shut off the part. Upon
expiration of the Soft−Start Timer, a low at the EN pin will shut the part off only if the SMPS output is out
of regulation, or the signal at the WDI input is not valid.
Logic compatible Synchronization input. Grounding this input allows a resistor between the ROSC pin
and ground to control the switching frequency. Connecting this pin to an external clock synchronizes
switching to the rising edge of the clock.
Oscillator frequency programming pin. Connect an external resistor from this pin to GND to set the
switching frequency. Leave this pin floating to operate at the default frequency of the internal oscillator.
Switching frequency is not controlled by this resistance if a clock is present at the SYNC pin, but the
resistance remains in control of the modulator ramp amplitude.
Battery return, and ground reference for output voltages.
Switching Regulator Error Amplifier output for tailoring SMPS transient response with external
compensation components.
Feedback input pin to program Switching Regulator output voltage, and detect a low or shorted SMPS
output condition.
Bootstrap input provides drive voltage higher than VIN to the SMPS N−channel Power Switch for
minimum switch R
capacitor from this pin to the SW pin, in close proximity to both pins.
Switching node of the Switching Regulator. Connect the SMPS output inductor and cathode of the SMPS
freewheeling diode to this pin.
Input voltage from battery. Place an input filter capacitor in close proximity to this pin.
Output of the internal 8.5 V linear regulator. This provides regulated gate drive voltage to the SMPS
Power Switch. For a typical application connect a 4.7 mF ceramic capacitor in series with 0.5 W from this
pin to ground.
This open drain output is pulled low if either the 5P0 or 8P5 output is out of regulation.
Output of the internal 5 V linear regulator. For a typical application connect a 4.7 mF ceramic capacitor in
series with 0.5 W from this pin to ground.
Solder this to a low thermal impedance path for cooling.
DS(on)
and highest efficiency. For a typical application connect a 0.1 mF ceramic
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Description