NCV8881
1.5A Automotive Buck
Regulator with Watchdog
The NCV8881 consists of a Buck switching regulator (SMPS) with
a combination SMPS output undervoltage monitor and CPU watchdog
circuit. In addition, two fixed−voltage low dropout regulator outputs
are provided, and share an LDO output voltage status output. Once
enabled, regulator operation continues until the Watchdog signal is no
longer present. The NCV8881 is intended for Automotive,
battery−connected applications that must withstand a 40 V load dump.
The switching regulator is capable of converting the typical 9 V to
19 V automotive input voltage range to outputs from 3.3 V to 8 V at a
constant switching frequency, which can be resistor programmed or
synchronized to an external clock signal. Enable input threshold and
hysteresis are programmable, with the enable input state replicated at
an open drain Ignition Buffer output. The regulators are protected by
current limiting, input overvoltage and overtemperature shutdown, as
well as SMPS short circuit shutdown.
Features
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MARKING
DIAGRAMS
16
16
1
1
A
WL
YY
WW
G
= Assembly Location
= Wafer Lot
= Year
= Work Week
= Pb−Free Package
SO−16W EP
PW SUFFIX
CASE 751AG
NCV8881
AWLYYWWG
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
1.5 A Switching Regulator (internal power switch)
100 mA, 5 V LDO Output
40 mA, 8.5 V LDO Output
Operating Range 5 V to 19 V
Programmable SMPS Frequency
SMPS can be Synchronized to an External Clock
Programmable SMPS Output Voltage Down to 0.8 V
$2%
Reference Voltage Tolerance
Internal SMPS Soft−Start
Voltage−mode SMPS Control
SMPS Cycle−by−Cycle Current Limit and Short−Circuit Protection
Internal Bootstrap Diode
Logic level Enable Input
Enable Input Hysteresis Programmable by External Resistor Divider
Enable Input State is Replicated at an Open Drain Output
CPU Watchdog with Resistor Programmable Delays
Watchdog Reset Output also Indicates SMPS Output Out of Regulation
Battery Input Withstands Load Dump to 40 V
Low Standby Current
Thermal Shutdown (TSD)
NCV Prefix for Automotive and Other Applications Requiring Site
and Change Controls
•
These are Pb−Free Devices
Applications
(Note: Microdot may be in either location)
PIN CONNECTIONS
IGNBUF
WDI
RDLY
RESB
EN
SYNC
ROSC
GND
1
16
5P0
LDOMON
8P5
VIN
SW
BST
FB
COMP
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 32 of this data sheet.
•
Audio
•
Infotainment
•
Safety – Vision Systems
•
Instrumentation
©
Semiconductor Components Industries, LLC, 2011
January, 2011
−
Rev. 1
1
Publication Order Number:
NCV8881/D
NCV8881
IGNITION
RIGBUF
BUFFER
REGULATED
5.0V
CS5P0
LDO
MONITOR
IGNBUF
5P0
RMON
FROM CPU
WATCHDOG OUT
WDI
LDOMON
RDLY
RDLY
8P5
BEAD
REGULATED
8.5V
CS8P5
BATTERY
C8P5
TO CPU
RESET
RRESB
RESB
VIN
CIN
ENABLE
R1
EN
R2
SW
CBST
DFW
REGULATED
SMPS OUTPUT
L1
COUT
CZ1
RP2
SYNC
SYNC
BST
RFB1
ROSC
ROSC
FB
CP1
RZ1
RFB2
CP3
GND
COMP
Figure 1. Typical Application
IGNITION
BUFFER
RIGBUF
IGNBUF
1
BUFFERED
ENABLE
LOGIC
QLM
5P0
16
RMON
LDOMON
15
CS5
S+5
LDO
MONITOR
WATCHDOG
INPUT
QIB
WDI
2
RDLY
3
RDLY
TSD
TEMP
SENSE
DBST2
MONITOR
WATCHDOG
TIMER
NOPULSE
DBST1
8P5
14
C8P5
BEAD
S+8.5
5V
REGULATOR
VIN_OV
/UVLO
FAULT(H)
8.5V
REGULATOR
VIN
13
CS8P5
CPU
RESET
BATTERY
RRESB
RESB
4
ENABLE
R1
R2
QRB
EN
5
CLAMP
RH
ENABLE
POWER
SWITCH
SW
12
BST
11
SW_UV
CBST
L1
CIN
SWITCHER
OUT
QH
HYSTERESIS
DFW
COUT
UNDERVOLTAGE
MONITOR
SHORT CKT
MONITOR
ERROR
AMP
REF
FB
10
CP1
RZ1
CZ1
RP2
RFB1
OC
RUN
SYNC
SYNC
6
ROSC
7
ROSC
GND
8
OSCILLATOR
PWM
COMPARATOR
CP3
RFB2
NCV8881
COMP
9
Figure 2. NCV8881 Detailed Block Diagram
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2
NCV8881
MAXIMUM RATINGS
Rating
Min/Max Voltage on WDI
Min/Max Voltage on RDLY
Min/Max Voltage on RESB
Min/Max Voltage on EN
Max EN Current
Min EN Current (with zero VIN voltage)
Min/Max Voltage on SYNC
Min/Max Voltage on ROSC
Min/Max Voltage COMP
Min/Max Voltage FB
Min Voltage SW
Max Voltage VIN to SW
Max Voltage VIN
Min/Max Voltage BST
Min/Max Voltage BST to SW
Min/Max Voltage on 8P5
Max 8P5 Current
Min/Max Voltage on LDOMON
Min/Max Voltage on 5P0
Min/Max Voltage IGNBUF
Storage Temperature range
Operating Junction Temperature Range
ESD withstand Voltage Human Body Model
Machine Model
Charged Device Model
T
J
V
ESD
– DC
−
20 ns
Symbol
Value
−0.3
to 7
−0.3
to 7
−0.3
to 7
−0.3
to 10
10
−10
−0.3
to 7
−0.3
to 7
−0.3
to 7
−0.3
to 7
−0.7
−3
40
40
−0.3
to 30
−0.3
to 15
−0.3
to 9.5
70
−0.3
to 7
−0.3
to 7
−0.3
to 7
−55
to +150
−40
to + 150
2.0
200
>1.0
Level 1
260
°C
Unit
V
V
V
V
mA
mA
V
V
V
V
V
V
V
V
V
V
mA
V
V
V
°C
°C
kV
V
kV
Moisture Sensitivity
Peak Reflow Soldering Temperature
MSL
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
THERMAL CHARACTERISTICS
Board/Mounting Conditions Typical Value
Parameter
Junction−to−case top (Y
JT
,
q
JT
)
Junction−to−pin 1(Y
JL1
,
q
JL1
)
Junction−to−board (Y
JB
,
q
JB
) (Note 3)
Junction−to−ambient (R
qJA
,
q
JA
)
Minimum Pad (Note 1)
30
70
15
150
1 sq. inch (Note 2)
16
65
17
55
Unit
°C/W
°C/W
°C/W
°C/W
Specific Notes on Thermal Characterization Conditions:
All boards are 0.062” thick FR4, 3” square, with varying amounts of copper heat spreader, in still air (free convection) conditions.
Numerical values are derived from an axisymmetric finite−element model where active die area, total die area, flag area, pad area,
and board area are equated to the actual corresponding areas.
1. 1 oz. copper, 17.2 mm
2
spreader area (minimum exposed pad, not including traces which are assumed).
2. 1 oz. copper, 645 mm
2
(1 in
2
) spreader area (includes exposed pad).
3. “Board” is defined as center of exposed pad soldered to board; this is the recommended number to be used for thermal calculations, as it
best represents the primary heat flow path and is least sensitive to board and ambient properties.
NOTE:
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3
NCV8881
PIN FUNCTION DESCRIPTIONS
Pin No.
1
2
3
4
Symbol
IGNBUF
WDI
RDLY
RESB
Description
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
DS(on)
and highest efficiency. For a typical application connect a 0.1
mF
ceramic
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.
5
EN
6
SYNC
7
ROSC
8
9
10
11
GND
COMP
FB
BST
12
13
14
SW
VIN
8P5
15
16
LDOMON
5P0
EXPOSED
PAD
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4
NCV8881
GENERAL SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
(V
VIN
=
13.2 V, V
EN
= 2.0 V, C
IN
= 4.7
mF
unless specified otherwise) Min/Max values are valid
for the temperature range
−40°C
vT
J
v
150
°C
unless noted otherwise, and are guaranteed by test, design or statistical correlation.
Parameter
VIN UVLO
START Voltage Threshold
STOP Voltage Threshold
VIN UVLO Hysteresis
VIN OVERVOLTAGE
STOP Voltage Threshold
RESTART Voltage Threshold
QUIESCENT CURRENT
VIN Quiescent Current
VIN Shutdown Current
ENABLE (EN PIN)
EN Logic High Threshold
EN Logic Low Threshold
EN Input Current
EN Input Current
Response to Open Input
Enable Delay
Clamp Current
Clamp Voltage
IGNITION BUFFER (IGNBUF PIN)
IGNBUF Output leakage
IGNBUF Output Voltage Low
THERMAL SHUTDOWN (TSD)
Thermal Shutdown
Thermal Shutdown Hysteresis
4. Guaranteed by design.
T
TSD
(Note 4)
(Note 4)
160
170
35
180
°C
°C
V
IGBLO
V
EN
> 1.6 V
V
EN
< 1.2 V, sinking 0.5 mA
0
0.02
5
0.1
mA
V
EN high to LDO turn−on
V
EN
= 5 V
I
EN
= 10 mA
9
V
ENSTHH
V
ENSTHL
I
ENSWL
I
ENSWH
V
EN
= 1.2 V
V
EN
= 1.6 V
1.2
35
0.8
42
1.4
55
3.0
1.6
V
V
mA
mA
I
qMAX
I
qSBMAX
V
FB
= 1 V, T
J
=
25°C, V
SW
= 0 V
V
EN
= 0 V, T
J
=
25°C, V
SW
= 0 V
2
10
5
15
mA
mA
V
OVSTP
V
OVSTT
19
18
20
19.2
21
V
V
V
STRT
V
STP
V
INHYST
5.0
4.2
0.7
5.6
4.6
1.1
6.0
5.0
V
V
V
Symbol
Conditions
Min
Typ
Max
Unit
NCV8881 is disabled
38
5
10.5
50
20
12
ms
mA
V
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5
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