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PDF NCP3231 Data sheet ( Hoja de datos )
| Número de pieza | NCP3231 | |
| Descripción | High Current Synchronous Buck Converter | |
| Fabricantes | ON Semiconductor | |
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NCP3231
High Current Synchronous
Buck Converter
The NCP3231 is a high current, high efficiency, voltage−feed−
forward voltage−mode synchronous buck converter which operates
from 4.5 V to 18 V input and generates output voltages down to 0.6 V
at up to 25 A DC load or 30 A instantaneous load.
Features
• Wide Input Voltage Range from 4.5 V to 18 V
• 0.6 V Internal Reference Voltage
• 500 kHz Switching Frequency
• External Programmable Soft−start
• Lossless Low−side FET Current Sensing
• Output Over−voltage Protection and Under−voltage Protection
• System Over−temperature Protection using a Thermistor or Sensor
• Hiccup Mode Operation for All Faults
• Pre−bias Start−up
• Adjustable Output Voltage
• Power Good Output
• Internal Over−temperature Protection
• This is a Pb−Free Device*
Typical Applications
• Cellular Base Stations
• ASIC, FPGA, DSP and CPU Core and I/O Supplies
• Telecom and Network Equipment
• Server and Storage System
www.onsemi.com
1 40
QFN40 6x6, 0.5P
CASE 485CM
MARKING
DIAGRAM
1
NCP3231
AWLYYWWG
NCP3231
A
WL
YY
WW
G
= Specific Device Code
= Assembly Location
= Wafer Lot
= Year
= Work Week
= Pb−Free Package
PIN CONNECTIONS
VIN 11
VIN 12
VIN 13
VIN 14
VSWH 15
PGND 16
PGND 17
PGND 18
PGND 19
PGND 20
VIN
EP42
GND
EP41
VSWH
EP43
40 EN
39 VCC
38 VB
37 PGND
36 BST
35 VSW
34 VSWH
33 VSWH
32 VSWH
31 VSWH
(TOP VIEW)
*For additional information on our Pb−Free strategy and soldering details, please
download the ON Semiconductor Soldering and Mounting Techniques
Reference Manual, SOLDERRM/D.
ORDERING INFORMATION
Device
Package
NCP3231MNTXG QFN−40
(Pb−Free)
Shipping†
2500 /
Tape & Reel
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specification
Brochure, BRD8011/D.
© Semiconductor Components Industries, LLC, 2015
May, 2015 − Rev. 5
1
Publication Order Number:
NCP3231/D
1 page  
NCP3231
ELECTRICAL CHARACTERISTICS
(−40°C < TJ < +125°C, VCC = 12 V, for min/max values unless otherwise noted, TJ = +25°C for typical values)
Parameter
Symbol
Test Conditions
Min Typ
Max Units
POWER SUPPLY
VIN/VCC Operation Voltage
VIN/VCC
4.5 18 V
VB UVLO Threshold (Rising)
4.1 4.2 4.3 V
VB UVLO Threshold (Falling)
3.4 3.66 3.8
V
VB Output Voltage
VB
VCC = 6 V, 0 ≤ IB ≤ 40 mA
4.9 5.15 5.45 V
VB Dropout Voltage
IB = 25 mA, VCC = 4.5 V
36 110 mV
VCC Quiescent Current
EN = H, COMP = H, no switching;
PG open; no switching
4.7 6.1 mA
Shutdown Supply Current
FEEDBACK VOLTAGE
NCP3231; EN = 0; VCC = 18 V; PG open
NCP3231; EN = 0; VCC = 4.5 V; PG open
100 140 mA
53 70 mA
FB Input Voltage
Feedback Input Bias Current
VFB
TJ = 25°C, 4.5 V ≤ VCC ≤ 18 V
0.597 0.6 0.603 V
−40°C ≤ TJ ≤ 125°C; 4.5 V ≤ VCC ≤ 18 V 0.594 0.6 0.606
IFB VFB = 0.6 V
75 nA
ERROR AMPLIFIER
Open Loop DC Gain (Note 4)
60 85
dB
Open Loop Unity Gain Bandwidth
F0dB,EA
24 MHz
Open Loop Phase Margin
60 °
Slew Rate
COMP Clamp Voltage, High
COMP pin to GND = 10 pF
2.5 V/m
3.46 V
COMP Clamp Voltage, Low
465 mV
Output Source Current
VFB = 0 V
15
mA
Output Sink Current
CURRENT LIMIT
VFB = 1 V
20
mA
Low−side ISET Current Source
Low−side ISET Current Source
Temperature Coefficient
LS_ISET
TC_LS_I−
SET
Sourced from ISET pin, before SS,
TJ = 25°C
30.5 33 35.5 mA
+0.31
%/°C
Low−side OCP Switch−over
Threshold (Note 4)
600 mV
Low−side Fixed OCP Threshold
(Note 4)
LS_OCPth
300 mV
Low−side Programmable OCP Range LS_OCPth
< 600 mV
LS OCP Blanking time (Note 4)
LS_Tblnk
150 ns
PWM
Maximum duty cycle
fsw = 500 kHz, VFB = 0 V
4.5 V < VCC < 18 V
92 %
Minimum duty cycle
VCOMP < PWM Ramp Offset Voltage
0
%
Minimum GH on−time (Note 3)
60 ns
PWM Ramp Amplitude (Note 3)
VCC/8.6 VCC/6.6 VCC/5.6 V
PWM Ramp Offset (Note 3)
0.64 V
3. Guaranteed by characterization
4. Guaranteed by design
www.onsemi.com
5
5 Page 
NCP3231
OPERATION DESCRIPTION
Overview
The NCP3231 is a 500 kHz, high efficiency, high current
PWM synchronous buck converter. It operates with a single
supply voltage from 4.5 to 18 V and can provide output
current as high as 30 A. NCP3231 utilizes voltage mode with
voltage feed−forward control to respond instantly to Vin
changes and provide for easier compensation over the
supply range of the converter. The device also includes
pre−bias startup capability to allow monotonic startup in the
event of a pre−biased output condition.
Protection features include overcurrent protection (OCP),
output over and under voltage protection (OVP, UVP), and
power good. The enable function is highly programmable to
allow for adjustable startup voltages at higher input
voltages. There is also an adjustable soft−start, an over−
temperature comparator, and internal thermal shutdown.
Reference Voltage
The NCP3231 incorporates an internal reference that
allows output voltages as low as 0.6 V. The tolerance of the
internal reference is guaranteed over the entire operating
temperature range of the controller. The reference voltage is
trimmed using a test configuration that accounts for error
amplifier offset and bias currents.
Oscillator Ramp
The ramp waveform is a saw tooth formed at the PWM
frequency with a peak−to−peak amplitude of VCC/6.6,
offset from GND by typically 0.64 V. The PWM duty cycle
is limited to a typical 92%, allowing the bootstrap capacitor
to charge during each cycle.
Error Amplifier
The error amplifier’s primary function is to regulate the
converter’s output voltage using a resistor divider connected
from the converter’s output to the FB pin of the controller,
as shown in the Applications Schematic. A type III
compensation network must be connected around the error
amplifier to stabilize the converter. It has a bandwidth of
greater than 24 MHz, with open loop gain of at least 60 dB.
Programmable Soft−Start
An external capacitor connected from the SS pin to
ground sets up the soft start period, which can limit the
start−up inrush current. The soft start period can be
programmed based on the Equation 1.
tSS
+
CSS
ISS
Vref
(eq. 1)
OCP is the only fault that is active during a soft−start.
Adaptive Non−Overlap Gate Driver
In a synchronous buck converter, a certain dead time is
required between the low side drive signal and high side
drive signal to avoid shoot through. During the dead time,
the body diode of the low side FET freewheels the current.
NCP3231 implements adaptive dead time control to
minimize the dead time, as well as preventing shoot through.
Precision Enable (EN)
The ENABLE block allows the output to be toggled on
and off and is a precision analog input.
When the EN voltage exceeds V_EN, the controller will
initiate the soft−start sequence as long as the input voltage
and sub−regulated voltage have exceeded their UVLO
thresholds. V_EN_hyst helps to reject noise and allow the
pin to be resistively coupled to the input voltage or
sequenced with other rails.
If the EN voltage is held below typically 0.8 V, the
NCP3231 enters a deep disable state where the internal bias
circuitry is off. As the voltage at EN continues to rise, the
Enable comparator and reference are active and provide a
more accurate EN threshold. The drivers are held off until
the rising voltage at EN crosses V_EN.
An internal 2 mA pullup automatically enables the device
when the EN pin is left floating.
INPUT SUPPLY / VCC
VDD
2 mA
EN
1.2 V
Enable
Logic
Figure 22. Enable Functional Block Diagram
Pre−bias Startup
In some applications the controller will be required to start
switching when its output capacitors are charged anywhere
from slightly above 0 V to just below the regulation voltage.
This situation occurs for a number of reasons: the
converter’s output capacitors may have residual charge on
them or the converter’s output may be held up by a low
current standby power supply. NCP3231 supports pre−bias
start up by holding off switching until the feedback voltage
and thus the output voltage rises above the set regulated
voltage. If the pre−bias voltage is higher than the set
regulated voltage, switching does not occur until the output
voltage drops back to the regulation point.
www.onsemi.com
11
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet NCP3231.PDF ] | |
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