ncv8881 ON Semiconductor, ncv8881 Datasheet - Page 22

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

IGNITION BUFFER
voltage level (high or low) detected by the EN input circuitry
when the EN signal is latched. The NCV8881 will pull the
IGNBUF output low if the Enable signal is low, and release
the IGNBUF output if the Enable signal is high. The
IGNBUF output is an open drain device which requires an
external pullup resistor to a logic supply. IGNBUF is no
longer controlled by EN when EN transitions low if the EN
signal is not latched.
THERMAL SHUTDOWN
the Soft−start circuit, and power down the 5P0 and 8P5
outputs if internal die temperature exceeds a safe level.
Operation is automatically restored when die temperature
has dropped below the thermal restart threshold regardless
of the state of the EN signal.
5P0 OUTPUT
CURRENT LIMIT
current capability in order to limit inrush current at turn−on
and also minimize power dissipation in the event of an
output short circuit.
OUTPUT UNDERVOLTAGE MONITOR
8P5 output voltage must exceed V
will begin soft−start. If the output is below V
LDOMON output will be pulled low.
STABILITY CONSIDERATIONS
performance characteristics of a linear regulator: starting
delay, load transient response, and loop stability. The
optimum capacitor type and value will depend on these three
characteristics, as well as cost, availability, size and
temperature constraints. Tantalum, aluminum electrolytic,
film, and ceramic are all acceptable capacitor types for most
applications. Values of 1 mF or more work in many cases,
however attention must be paid to the Equivalent Series
Resistance (ESR). Aluminum electrolytic capacitors are the
least expensive solution but both the value and ESR of this
type of capacitor change considerably at low temperatures
(−25°C or −40°C). The capacitor manufacturer’s data sheet
must be consulted for this information. Stability under all
load and temperature conditions is guaranteed by a capacitor
value greater than or equal to 4.7 mF and ESR between 0.2
and 5 W.
used to provide a regulated voltage to an ROSC pullup
resistor as a convenient way to decrease the factory−set
switching frequency.
The Ignition Buffer output IGNBUF reports the EN pin
A thermal shutdown circuit will inhibit switching, reset
5P0 output current is limited above the specified output
Either the 5P0 output voltage must exceed V
The output capacitor helps determine three main
Besides powering external loads, the 5P0 output can be
8UVSTT
before the SMPS
5UVSTT
5UVSTP
http://onsemi.com
or the
, the
22
8P5 OUTPUT
to power the internal gate drive circuitry, but can also
provide current to modest external circuit loads that can
tolerate significant spike noise at the SMPS switching
frequency.
CURRENT LIMIT
current capability in order to limit inrush current at turn−on
and also minimize power dissipation in the event of an
output short circuit.
OUTPUT UNDERVOLTAGE MONITOR
5P0 output voltage must exceed V
will begin soft−start. The LDOMON output will be pulled
low if the 8P5 output voltage is below V
OUTPUT OVERVOLTAGE CLAMP
the voltage in order to protect the gate driver circuit from
excessive voltage.
STABILITY CONSIDERATIONS
performance characteristics of a linear regulator: starting
delay, load transient response, and loop stability. The
optimum capacitor type and value will depend on these three
characteristics, as well as cost, availability, size and
temperature constraints. Tantalum, aluminum electrolytic,
film, and ceramic are all acceptable capacitor types for most
applications. Values of 1 mF or more work in many cases,
however attention must be paid to the Equivalent Series
Resistance (ESR). Aluminum electrolytic capacitors are the
least expensive solution but both the value and ESR of this
type of capacitor change considerably at low temperatures
(−25°C or −40°C). The capacitor manufacturer’s data sheet
must be consulted for this information. Stability under all
load and temperature conditions is guaranteed by a capacitor
value greater than or equal to 4.7 mF and ESR between 0.2 W
and 5 W.
SMPS OPERATION
LDO OUTPUT UNDERVOLTAGE MONITOR
and the EN input to be above V
output voltage must exceed V
voltage must exceed V
soft−start.
SOFT−START
conditions, and after one of the LDO outputs reaches
The regulated voltage provided by the 8P5 output is used
8P5 output current is limited above the specified output
Either the 8P5 output voltage must exceed V
If current is forced into the 8P5 output, a clamp will limit
The output capacitor helps determine three main
Besides requiring the input voltage to be above V
Upon being enabled and released from all fault
8UVSTT
before the SMPS will begin
5UVSTT
5UVSTT
ENSTHH
or the 8P5 output
8UVSTP
before the SMPS
, either the 5P0
8UVSTT
.
or the
STRT