© Semiconductor Components Industries, LLC, 2016
August, 2019 − Rev. 1
1Publication Order Number:
NCV891130/D
NCV891130
Step-Down Regulator -
Automotive, Low-Iq,
Dual-Mode
1.2 A, 2 MHz
The NCV891130 is a Dual Mode regulator intended for Automotive,
battery−connected applications that must operate with up to a 45 V
input supply. Depending on the output load, it operates either as a PWM
Buck Converter or as a Low Drop−Out Linear Regulator, and is suitable
for systems with low noise and Low Quiescent Current requirements
often encountered in automotive driver information systems. A reset
pin (with fixed delay) simplifies interfacing with a microcontroller.
The NCV891130 also provides several protection features expected
in automotive power supply systems such as current limit, short circuit
protection, and thermal shutdown. In addition, the high switching
frequency produces low output voltage ripple even when using small
inductor values and an all−ceramic output filter capacitor – forming a
space−efficient switching regulator solution.
Features
•30 mA Iq in Light Load Condition
•1.2 A Maximum Output Current in PWM Mode
•Internal N−channel Power Switch
•VIN Operating Range 3.7 V to 36 V
•Withstands Load Dump to 45 V
•Logic Level Enable Pin can be Tied to Battery
•Fixed Output Voltage of 5.0 V, 4.0 V or 3.3 V
•2 MHz Free−running Switching Frequency
•±2 % Output Voltage Accuracy
•NCV Prefix for Automotive Requiring Site and Control Changes
•These Devices are Pb−Free and are RoHS Compliant
Typical Applications
•Audio
•Infotainment
•Instrumentation
•Safety−Vision Systems
Figure 1. Typical Application
VIN
DRV
GND EN
SW
BST
VOUT
RSTB
VIN VOUT
CIN CBST
DBST
DFW COUT
L1
CDRV
NCV891130
EN
RESET
MARKING DIAGRAM
With XX = 33 for 3.3 V Output
= 40 for 4.0 V Output
= 50 for 5.0 V Output
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G= Pb−Free Device
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SOIC−8
EXPOSED PAD
CASE 751AC
1
8
1
8
891130XX
ALYW
G
VIN
DRV
GND
SW
BST
EN
VOUT
RSTB
1
2
3
4
8
7
6
5
PIN CONNECTIONS
See detailed ordering and shipping information on page 13 of
this data sheet.
ORDERING INFORMATION
(Top View)
NCV891130
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Figure 2. Simplified Block Diagram
VIN
DRV
GND
SW
BST
VOUT
EN
VIN VOUT
CIN
CBST
DBST
DFW COUT
L1
CDRV
NCV891130
PWM
LOGIC
OFF
ON
+
−
S
Oscillator
+
−
Soft−Start
RESET
3.3 V
Reg
VOLTAGES
MONITORS
Switcher Supply
TSD
+
+
LINEAR
REGULATOR
ON
ON
MODE
SELECTION OVLD
Low
+
+
−
+
Enable
EN
RSTB
1.2 A
detector
comp
RESET
Logic
Table 1. PIN FUNCTION DESCRIPTION
Pin No. Pin Name Description
1 VIN Input voltage from battery. Place an input filter capacitor in close proximity to this pin.
2 DRV Output voltage to provide a regulated voltage to the Power Switch gate driver.
3 RSTB Reset function. Open drain output, pulling down to ground when the output voltage is out of regulation.
4 GND Battery return, and output voltage ground reference.
5 EN This TTL compatible Enable input allows the direct connection of Battery as the enable signal. Grounding
this input stops switching and reduces quiescent current draw to a minimum.
6 VOUT Output voltage feedback and LDO output. Feedback of output voltage used for regulation, as well as LDO
output in LDO mode.
7 BST Bootstrap input provides drive voltage higher than VIN to the N−channel Power Switch for minimum
switch Rdson and highest efficiency.
8 SW Switching node of the Regulator. Connect the output inductor and cathode of the freewheeling diode to
this pin.
EPAD Connect to Pin 4 (electrical ground) and to a low thermal resistance path to the ambient temperature
environment.
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Table 2. ABSOLUTE MAXIMUM RATINGS
Rating Symbol Value Unit
Min/Max Voltage VIN −0.3 to 45 V
Max Voltage VIN to SW 45 V
Min/Max Voltage SW −0.7 to 40 V
Min Voltage SW − 20 ns −3.0 V
Min/Max Voltage EN −0.3 to 40 V
Min/Max Voltage VIN to EN −1.5 to 45 V
Min/Max Voltage BST −0.3 to 43 V
Min/Max Voltage BST to SW −0.3 to 3.6 V
Min/Max Voltage on RSTB −0.3 to 6 V
Min/Max Voltage VOUT −0.3 to 18 V
Min/Max Voltage DRV −0.3 to 3.6 V
Thermal Resistance, SOIC8−EP Junction–to–Ambient (Note 1) RθJA 30 °C/W
Storage Temperature range −55 to +150 °C
Operating Junction Temperature Range TJ−40 to +150 °C
ESD withstand Voltage (Note 2) Human Body Model VESD 2.0 kV
Moisture Sensitivity MSL Level 2
Peak Reflow Soldering Temperature (Note 3) 260 °C
Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality
should not be assumed, damage may occur and reliability may be affected.
1. Value based on 4 layers of 645 mm2 (or 1 in2) of 1 oz copper thickness on FR4 PCB substrate.
2. This device series incorporates ESD protection and is tested by the following methods:
ESD Human Body Model tested per AEC−Q100−002 (EIA/JESD22−A114)
Latchup Current Maximum Rating: v150 mA per JEDEC standard: JESD78
3. For information, please refer to our Soldering and Mounting Techniques Reference Manual, SOLDERRM/D
Table 3. ELECTRICAL CHARACTERISTICS
VIN = 4.5 to 28 V, VEN = 5 V, VBST = VSW + 3 V, CDRV = 0.1 mF, for typical values TJ = 25°C, Min/Max values are valid for the temperature
range −40°C v TJ v 150°C unless noted otherwise, and are guaranteed by test, design or statistical correlation (Notes 4, 5)
Parameter Test Conditions Symbol Min Typ Max Unit
QUIESCENT CURRENT
Quiescent Current, enabled VIN = 13.2 V, IOUT = 100 mA, 25°CIq30 39 mA
Quiescent Current, shutdown VIN = 13.2 V, VEN = 0 V, 25°C IqSD 9 12 mA
UNDERVOLTAGE LOCKOUT – VIN (UVLO)
UVLO Start Threshold VIN rising VUVLSTT 4.1 4.5 V
UVLO Stop Threshold VIN falling VUVLSTP 3.1 3.7 V
UVLO Hysteresis VUVLOHY 0.4 1.4 V
SOFT−START (SS)
Soft−Start Completion Time tSS 0.8 1.4 2.0 ms
OUTPUT VOLTAGE
Output Voltage during regulation 100 mA < IOUT < 1.2 A
5.0 V option
4.0 V option
3.3 V option
VOUTreg 4.9
3.92
3.234
5.0
4.0
3.3
5.1
4.08
3.366
V
4. Refer to ABSOLUTE MAXIMUM RATINGS and APPLICATION INFORMATION for Safe Operating Area.
5. Performance guaranteed over the indicated operating temperature range by design and/or characterization tested at TJ = TA = 25°C. Low
duty cycle pulse techniques are used during testing to maintain the junction temperature as close to ambient as possible.
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Table 3. ELECTRICAL CHARACTERISTICS
VIN = 4.5 to 28 V, VEN = 5 V, VBST = VSW + 3 V, CDRV = 0.1 mF, for typical values TJ = 25°C, Min/Max values are valid for the temperature
range −40°C v TJ v 150°C unless noted otherwise, and are guaranteed by test, design or statistical correlation (Notes 4, 5)
Parameter UnitMaxTypMinSymbolTest Conditions
OSCILLATOR
Frequency 4.5 < VIN < 18 V
20 V <VIN < 28V
FSW
FSW(HV)
1.8
0.9
2.0
1.0
2.2
1.1
MHz
VIN FREQUENCY FOLDBACK MONITOR
Frequency Foldback Threshold
VIN rising
VIN falling
VFLDUP
VFLDDN
18.4
18
20
19.8
V
Frequency Foldback Hysteresis VFLDHY 0.2 0.3 0.4 V
MODE TRANSITION
Normal to Low−Iq mode Current Threshold 8 V < VIN < 28 V INtoL 3 40 mA
Mode Transition Duration
Switcher to Linear
Linear to Switcher
tSWtoLIN
tLINtoSW
300
1 2
ms
Minimum time in Normal Mode before
starting to monitor output current
tSWblank 500 ms
Linear to switcher transition
at high Vin
at low Vin
VOUT = 3.3 V
VLINtoSW(HV)
VLINtoSW(LV)
19
3.6
28
4.5
V
PEAK CURRENT LIMIT
Current Limit Threshold ILIM 2.1 2.35 2.6 A
POWER SWITCH
ON Resistance VBST = VSW + 3.0 V RDSON 180 360 mW
Leakage current VIN to SW VSW = 0, −40°C v TJ v 85°C ILKSW 10 mA
Minimum ON Time Measured at SW pin tONMIN 45 70 ns
Minimum OFF Time Measured at SW pin
At FSW = 2 MHz (normal)
At FSW = 500 kHz (max duty cycle)
tOFFMIN
30
30
50 70
ns
SLOPE COMPENSATION
Ramp Slope
(With respect to switch current)
4.5 < VIN < 18 V
20 V <VIN < 28V
Sramp
Sramp(HV)
1.45
0.65
2.0
1.0
2.8
1.3
A/ms
LOW POWER LINEAR REGULATOR
Line Regulation IOUT = 5 mA, 6 V < VIN < 18 V VREG(line) 5 25 mV
Load Regulation VIN = 13.2 V, 0.1 mA < IOUT < 50 mA VREG(load) 5 35 mV
Power Supply Rejection VOUT(ripple) = 0.5 Vp−p, F = 100 Hz PSRR 65 dB
Current Limit ILIN(lim) 50 80 mA
Output clamp current VOUT = VOUTreg(typ) + 10% ICL(OUT) 0.5 1.0 1.5 mA
SHORT CIRCUIT DETECTOR
Switching frequency in short−circuit condi-
tion Analog Foldback
Analog foldback – high VIN
Hiccup Mode
VOUT = 0 V, 4.5 V < VIN < 18 V
VOUT = 0 V, 20 V <VIN < 28 V
FSWAF
FSWAFHV
FSWHIC
450
225
24
550
275
32
650
325
40
kHz
RESET
Leakage current into RSTB pin IRSTBlk 1 uA
4. Refer to ABSOLUTE MAXIMUM RATINGS and APPLICATION INFORMATION for Safe Operating Area.
5. Performance guaranteed over the indicated operating temperature range by design and/or characterization tested at TJ = TA = 25°C. Low
duty cycle pulse techniques are used during testing to maintain the junction temperature as close to ambient as possible.
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Table 3. ELECTRICAL CHARACTERISTICS
VIN = 4.5 to 28 V, VEN = 5 V, VBST = VSW + 3 V, CDRV = 0.1 mF, for typical values TJ = 25°C, Min/Max values are valid for the temperature
range −40°C v TJ v 150°C unless noted otherwise, and are guaranteed by test, design or statistical correlation (Notes 4, 5)
Parameter UnitMaxTypMinSymbolTest Conditions
RESET
Output voltage threshold at which the RSTB
signal goes low
VOUT decreasing
5.0 V option
4.0 V option
3.3 V option
VRESET 4.50
3.6
2.97
4.625
3.7
3.05
4.75
3.8
3.14
V
Hysteresis on RSTB threshold VOUT increasing
5.0 V option
4.0 V option
3.3 V option
VREShys 25
20
17
60
50
40
100
80
66
mV
Noise−filtering delay From VOUT<VRESET to RSTB pin
going low
tfilter 10 25 ms
Restart Delay time From VOUT>VRESET+VREShys to
high RSTB
tdelay 14 16 18 ms
Low RSTB voltage RRSTBpullup = VOUTreg/1 mA, VOUT > 1 V VRSTBlow 0.4 V
GATE VOLTAGE SUPPLY (DRV pin)
Output Voltage VDRV 3.1 3.3 3.5 V
DRV UVLO START Threshold VDRVSTT 2.7 2.9 3.05 V
DRV UVLO STOP Threshold VDRVSTP 2.5 2.8 3.0 V
DRV UVLO Hysteresis VDRVHYS 50 200 mV
DRV Current Limit VDRV = 0 V IDRVLIM 21 50 mA
VIN OVERVOLTAGE SHUTDOWN MONITOR
Overvoltage Stop Threshold VIN increasing VOVSTP 36.5 37.7 39.0 V
Overvoltage Start Threshold VIN decreasing VOVSTT 36.0 37.3 38.8 V
Overvoltage Hysteresis VOVHY 0.25 0.40 0.50 V
ENABLE (EN)
Logic low threshold voltage VENlow 0.8 V
Logic high threshold voltage VENhigh 2 V
EN pin input current IENbias 0.2 1 mA
THERMAL SHUTDOWN
Activation Temperature TSD 155 190 °C
Reset temperature TSDrestart 135 185 °C
Hysteresis THYS 5 20 °C
4. Refer to ABSOLUTE MAXIMUM RATINGS and APPLICATION INFORMATION for Safe Operating Area.
5. Performance guaranteed over the indicated operating temperature range by design and/or characterization tested at TJ = TA = 25°C. Low
duty cycle pulse techniques are used during testing to maintain the junction temperature as close to ambient as possible.
Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product
performance may not be indicated by the Electrical Characteristics if operated under different conditions.
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TYPICAL CHARACTERISTICS
Figure 3. No−load Input Current at TJ = 255C
vs. Input Voltage
Figure 4. Input Current at TJ = 255C vs. Output
Current
INPUT VOLTAGE (V) OUTPUT CURRENT (mA)
20151050
0
10
20
30
40
50
70
80
10008006004002000
0
200
400
600
800
1000
Figure 5. Low−Iq Mode Quiescent Current vs.
Junction Temperature
Figure 6. Shutdown Mode Quiescent Current
vs. Junction Temperature
TEMPERATURE (°C) TEMPERATURE (°C)
150100500−50
0
20
40
60
80
100
150100500−50
7
8
9
10
11
12
13
Figure 7. Switching Mode Quiescent Current
vs. Junction Temperature
Figure 8. 3.3 V Output Voltage vs. Junction
Temperature
TEMPERATURE (°C) TEMPERATURE (°C)
150100500−50
1.2
1.3
1.4
1.5
1.6
150100500−50
3.24
3.26
3.28
3.29
3.31
3.33
3.35
NO LOAD INPUT CURRENT (mA)
INPUT CURRENT (mA)
Iq IN LOW−Iq LINEAR MODE (mA)
Iq IN SHUTDOWN MODE (mA)
Iq IN SWITCHER MODE (mA)
3.3 V OUTPUT VOLTAGE (V)
60
Switcher Mode
Low−Iq Mode
3.25
3.27
3.30
3.32
3.34
3.36
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TYPICAL CHARACTERISTICS
Figure 9. 4.0 V Output Voltage vs. Junction
Temperature
Figure 10. 5.0 V Output Voltage vs. Junction
Temperature
TEMPERATURE (°C) TEMPERATURE (°C)
150100500−50
3.94
3.95
3.97
3.98
4.00
4.02
4.03
4.05
150100500−50
4.94
4.95
4.97
4.98
5.00
5.02
5.04
5.05
Figure 11. Switching Frequency vs. Junction
Temperature
Figure 12. Minimum On Time vs. Junction
Temperature
TEMPERATURE (°C) TEMPERATURE (°C)
150100500−50
1.8
1.9
2.0
2.1
2.2
150100500−50
52
53
54
55
56
57
Figure 13. Peak Current Limit vs. Junction
Temperature
Figure 14. Peak Current Limit vs. Junction
Temperature
TEMPERATURE (°C) TEMPERATURE (°C)
150100500−50
2.1
2.2
2.3
2.4
2.5
150100500−50
4.2
4.3
4.4
4.5
4.6
4.7
4 V OUTPUT VOLTAGE (V)
5 V OUTPUT VOLTAGE (V)
SWITCHING FREQUENCY (MHz)
MINIMUM ON TIME (ns)
PEAK CURRENT LIMIT (A)
PEAK CURRENT LIMIT (A)
Switcher Mode
Low−Iq Mode
3.96
3.99
4.01
4.04
4.96
4.99
5.01
5.03
Switcher Mode
Low−Iq Mode
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TYPICAL CHARACTERISTICS
Figure 15. UVLO Thresholds vs. Junction
Temperature
Figure 16. Input Overvoltage Thresholds vs.
Junction Temperature
TEMPERATURE (°C) TEMPERATURE (°C)
150100500−50
3.0
3.2
3.4
3.6
3.8
4.0
4.4
4.6
150100500−50
34
35
36
37
38
39
40
Figure 17. Soft−start Duration vs. Junction
Temperature
Figure 18. DRV Voltage vs. Junction
Temperature
TEMPERATURE (°C) TEMPERATURE (°C)
150100500−50
1.40
1.45
1.50
1.55
1.60
150100500−50
3.0
3.1
3.2
3.3
3.4
3.5
Figure 19. DRV Voltage UVLO Tresholds vs.
Junction Temperature
Figure 20. Frequency Foldback Voltage
Tresholds vs. Junction Temperature
TEMPERATURE (°C) TEMPERATURE (°C)
150100500−50
2.6
2.8
3.0
150100500−50
18.0
18.2
18.6
18.8
19.0
19.2
19.6
19.8
UVLO THRESHOLDS (V)
OVERVOLTAGE THRESHOLDS (V)
SOFT−START TIME (ms)
DRV VOLTAGE (V)
DRV UVLO THRESHOLDS (V)
4.2
UVLO Threshold
Start−up Threshold
Restart Threshold
Overvoltage Threshold
IDRV = 0 mA
IDRV = 21 mA
2.7
2.9
FREQUENCY FOLDBACK VIN THRESHOLDS (V)
DRV UVLO Threshold
DRV Start−up Threshold
18.4
19.4
VIN Rising
VIN Falling
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TYPICAL CHARACTERISTICS
Figure 21. Foldback Frequency vs. Junction
Temperature
Figure 22. 3.3 V Version RESET Thresholds vs.
Junction Temperature
TEMPERATURE (°C) TEMPERATURE (°C)
150100500−50
0.90
0.95
1.00
1.05
1.10
150100500−50
2.8
2.9
3.0
3.2
3.3
Figure 23. 4.0 V Version RESET Thresholds vs.
Junction Temperature
Figure 24. 5.0 V Version RESET Thresholds vs.
Junction Temperature
TEMPERATURE (°C) TEMPERATURE (°C)
150100500−50
3.4
3.5
3.6
3.7
3.8
3.9
4.0
150100500−50
4.3
4.4
4.5
4.6
4.7
4.8
4.9
5.0
Figure 25. RESET Delay vs. Junction
Temperature
Figure 26. Low−Iq to Switcher Mode Transition
vs. Junction Temperature
TEMPERATURE (°C) TEMPERATURE (°C)
150100500−50
15.4
15.6
15.8
16.0
16.4
16.6
16.8
17.0
150100500−50
55
57
59
61
63
65
69
71
SWITCHING FREQUENCY AT HIGH VIN (MHz)
3.3 V RESET VOUT THRESHOLDS (V)
4 V RESET VOUT THRESHOLDS (V)
5 V RESET VOUT THRESHOLDS (V)
RESET DELAY (ms)
LINEAR TO SWITCHER MODE
CURRENT THRESHOLD (mA)
RSTB Toggles High (VOUT Rising)
RSTB Toggles Low (VOUT Falling)
RSTB Toggles High (VOUT Rising)
RSTB Toggles Low (VOUT Falling)
RSTB Toggles High (VOUT Rising)
RSTB Toggles Low (VOUT Falling)
16.2
67
3.1
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TYPICAL CHARACTERISTICS
Figure 27. Switcher to Low−Iq Mode Transition
(3.3 V Version, 2.2 mH) vs. Input Voltage
Figure 28. Switcher to Low−Iq Mode Transition
(5.0 V Version, 2.2 mH) vs. Input Voltage
INPUT VOLTAGE (V) INPUT VOLTAGE (V)
CURRENT RANGE FOR LOW−Iq
TRANSITION − 3.3 V VERSION (mA)
CURRENT RANGE FOR LOW−Iq
TRANSITION − 5 V VERSION (mA)
510 18
10
20
30
15
0
510 18
10
20
30
15
0
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APPLICATION INFORMATION
Hybrid Low−Power Mode
A high−frequency switch−mode regulator is not very
efficient in light load conditions, making it difficult to
achieve low−Iq requirements for sleep−mode operation. To
remedy this, the NCV891130 includes a low−Iq linear
regulator that turns on at light load, while the PWM
regulator turns off, ensuring a high−efficiency low−power
operation. Another advantage of the low−power mode is the
tight regulation free of voltage ripple usually associated with
low−Iq switchers in light load conditions. In either mode, the
NCV891130 meets the 2% output voltage regulation
specification.
At initial start−up the NCV891130 will soft−start into
PWM converter mode regardless of output current. During
a 300 s period, the NCV891130 will assess the level of
output current. The NCV891130 will not make the
assessment if RSTB is low. If the output current is above the
INtoL threshold, the NCV891130 will stay in PWM mode.
Otherwise, the NCV891130 will transition to low power
mode.
It will stay in this low−power mode until the output current
exceeds the ILIN(lim) limit: it then transitions back to PWM
converter mode. This low−power mode to PWM mode
transition happens within 2 s. The transient response is not
affected by the mode change.
Once the NCV891130 has transitioned to switcher mode,
a 500 s blanking period will occur. After the blanking period,
the NCV891130 will reassess the output current level. If the
output current level is below the INtoL threshold, the
NCV891130 will enter low−Iq mode. If the NCV891130 is
in low−power mode and in normal battery range, it will
transition to switcher mode when VIN increases above
VLINtoSW(HV), regardless of the output current. Similarly, if
the NCV891130 is in PWM mode and VIN is higher than
VFLDUP
, it will not transition to low−power mode even if the
output current becomes lower than INtoL.
At low input voltage, the NCV891130 stays in low−power
mode down to VLINtoSW(LV) if it entered this mode while in
normal battery range. However it may not enter low−power
mode below 8 V depending on the charge of the bootstrap
capacitor (see Bootstrap section for details).
Input Voltage
An Undervoltage Lockout (UVLO) circuit monitors the
input, and can inhibit switching and reset the Soft−start
circuit if there is insufficient voltage for proper regulation.
Depending on the output conditions (voltage option and
loading), the NCV891130 may lose regulation and run in
drop−out mode before reaching the UVLO threshold: refer
to the Minimum Vin calculation tool for details. When the
input voltage drops low enough that the part cannot regulate
because it reaches its maximum duty cycle, the switching
frequency is divided down by up to 4 (down to 500 kHz).
This helps lowering the minimum voltage at which the
regulator loses regulation.
An overvoltage monitoring circuit automatically
terminates switching if the input voltage exceeds VOVSTP
(see Figure 29), but the NCV891130 can withstand input
voltages up to 45 V.
To avoid skipping switching pulses and entering an
uncontrolled mode of operation, the switching frequency is
reduced by a factor of 2 when the input voltage exceeds the
VIN Frequency Foldback threshold (see Figure 29).
Frequency reduction is automatically terminated when the
input voltage drops back below the VIN Frequency Foldback
threshold. This also helps to limit the power lost in switching
and generating the drive voltage for the Power Switch.
ÎÎÎ
ÎÎÎ
ÎÎÎ
ÎÎÎ
ÎÎÎ
ÎÎÎ
ÎÎÎ
ÎÎÎ
ÎÎÎ
3.5 18 20 36 VIN (V)
1
2
FSW
(MHz)
4539
Frequency
folds back
if drop−out
mode
Figure 29. NCV891130 Switching Frequency Profile vs. Input Voltage
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Soft−Start
Upon being enabled or released from a fault condition,
and after the DRV voltage is established, a soft−start circuit
ramps the switching regulator error amplifier reference
voltage to the final value. During soft−start, the average
switching frequency is lower until the output voltage
approaches regulation.
Slope Compensation
A fixed slope compensation signal is generated internally
and added to the sensed current to avoid increased output
voltage ripple due to bifurcation of inductor ripple current
at duty cycles above 50%. The fixed amplitude of the slope
compensation signal requires the inductor to be greater than
a minimum value, depending on output voltage, in order to
avoid sub−harmonic oscillations. The recommended inductor
values are 2.2 or 3.3 mH, although higher values are possible.
Current Limiting
Due to the ripple on the inductor current, the average
output current of a buck converter is lower than the peak
current setpoint of the regulator. Figure 30 shows – for a
2.2 mH inductor – how the variation of inductor peak current
with input voltage affects the maximum DC current the
NCV891130 can deliver to a load.
Figure 30. NCV891130 Load Current Capability with a 2.2 mH Inductor
Short Circuit Protection
During severe output overloads or short circuits, the
NCV891130 automatically reduces its switching frequency.
This creates duty cycles small enough to limit the peak
current in the power components, while maintaining the
ability to automatically reestablish the output voltage if the
overload is removed.
In more severe short−circuit conditions where the inductor
current is still too high after the switching frequency has fully
folded back, the regulator enters a hiccup mode that further
reduces the power dissipation and protects the system.
RESET Function
The RSTB pin is pulled low when the output voltage falls
below 7.5% of the nominal regulation level, and floats when
the output is properly regulated. A pull−up resistor tied to the
output is needed to generate a logic high signal on this open
drain pin. The pin can be left unconnected when not used.
When the output voltage drops out of regulation, the pin
goes low after a short noise−filtering delay (tfilter). It stays low
for a 16 ms delay time after the output goes back to regulation,
simplifying the connection to a micro−controller.
The RSTB pin is also pulled low immediately in case of VIN
overvoltage, Thermal shutdown, VIN UVLO or DRV UVLO.
Feedback Loop
All components of the feedback loop (output voltage
sensing, error amplifier and compensation) are integrated
inside the NCV891130, and are optimized to ensure
regulation and sufficient phase and gain margin for the
recommended conditions of operation.
Recommended conditions and components:
•Input: car battery
•Output: 3.3 V, 4 V or 5 V, with output current up to
1.2 A
•Output capacitor: one to three parallel ceramic 10 mF
capacitors
•Inductor: 2.2 mH to 3.3 mH
With these operating conditions and components, the
open loop transfer function has a phase margin greater than
50°.
NCV891130
www.onsemi.com
13
Bootstrap
At the DRV pin an internal regulator provides a ground−
referenced voltage to an external capacitor (CDRV), to allow
fast recharge of the external bootstrap capacitor (CBST) used
to supply power to the power switch gate driver. If the
voltage at the DRV pin goes below the DRV UVLO
Threshold VDRVSTP
, switching is inhibited and the
Soft−start circuit is reset, until the DRV pin voltage goes
back up above VDRVSTT.
The NCV891130 permanently monitors the bootstrap
capacitor, and always ensures it stays charged no matter
what the operating conditions are. As a result, the additional
charging current for the bootstrap capacitor may prevent the
regulator from entering Low−Iq mode at low input voltage.
Practically, the 5 V output version does not enter Low−Iq
mode for input voltages below 8 V, and the 4 V version for
input voltages below 6.5 V (see typical characteristics
curves for details).
Enable
The NCV891130 is designed to accept either a logic level
signal or battery voltage as an Enable signal. However if
voltages above 40 V are expected, EN should be tied to VIN
through a 10 kW resistor in order to limit the current flowing
into the overvoltage protection of the pin.
EN low induces a shutdown mode which shuts off the
regulator and minimizes its supply current to 9 mA typical by
disabling all functions.
Upon enabling, voltage is established at the DRV pin,
followed by a soft−start of the switching regulator output.
ORDERING INFORMATION
Device Output Package Shipping
NCV891130PD50R2G 5.0 V
SOIC−8 EP 2500 / Tape & Reel
NCV891130PD40R2G 4.0 V
NCV891130PD33R2G 3.3 V
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
NCV891130
www.onsemi.com
14
PACKAGE DIMENSIONS
SOIC−8 EP
CASE 751AC
ISSUE B
ÉÉÉ
ÉÉÉ
ÉÉ
ÉÉ
ÉÉ
ÉÉ
ÇÇ
ÇÇ
ÇÇ
H
C0.10
D
E1
A
D
PIN ONE
2 X
8 X
SEATING
PLANE
EXPOSED
GAUGE
PLANE
14
58
D
C0.10 A-B
2 X
E
B
e
C0.10
2 X
TOP VIEW
SIDE VIEW
BOTTOM VIEW
DETAIL A
END VIEW
SECTION A−A
8 X b
A-B0.25 D
C
C
C0.10
C0.20
A
A2
G
F
14
58
NOTES:
1. DIMENSIONS AND TOLERANCING PER
ASME Y14.5M, 1994.
2. DIMENSIONS IN MILLIMETERS (ANGLES
IN DEGREES).
3. DIMENSION b DOES NOT INCLUDE
DAMBAR PROTRUSION. ALLOWABLE
DAMBAR PROTRUSION SHALL BE
0.08 MM TOTAL IN EXCESS OF THE “b”
DIMENSION AT MAXIMUM MATERIAL
CONDITION.
4. DATUMS A AND B TO BE DETERMINED
AT DATUM PLANE H.
DIM MIN MAX
MILLIMETERS
A1.35 1.75
A1 0.00 0.10
A2 1.35 1.65
b0.31 0.51
b1 0.28 0.48
c0.17 0.25
c1 0.17 0.23
D4.90 BSC
E6.00 BSC
e1.27 BSC
L0.40 1.27
L1 1.04 REF
F2.24 3.20
G1.55 2.51
h0.25 0.50
q0 8
h
AA
DETAIL A
(b)
b1
c
c1
0.25
L
(L1) q
PAD
E1 3.90 BSC
__
A1
LOCATION
SOLDERING FOOTPRINT
Exposed
Pad
1.52
0.060
2.03
0.08
0.6
0.024
1.270
0.050
4.0
0.155
ǒmm
inchesǓ
SCALE 6:1
7.0
0.275
2.72
0.107
PUBLICATION ORDERING INFORMATION
N. American Technical Support: 800−282−9855 Toll Free
USA/Canada
Europe, Middle East and Africa Technical Support:
Phone: 421 33 790 2910
Japan Customer Focus Center
Phone: 81−3−5817−1050
NCV891130/D
LITERATURE FULFILLMENT:
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Order Literature: http://www.onsemi.com/orderlit
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