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PDF APW8715A Data sheet ( Hoja de datos )
| Número de pieza | APW8715A | |
| Descripción | High Input Voltage 6A PWM Converter | |
| Fabricantes | ANPEC | |
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APW8715A
High Input Voltage 6A PWM Converter With Adj. Soft Start
Features
General Description
• Adjustable Output Voltage from +0.8V to +12V
The APW8715A is a 6A, synchronous, step-down con-
- 0.8V Reference Voltage
verter with integrated 30mΩ N-channel High-Side
- +1% Accuracy over Temperature
MOSFET and 12mΩ Low-Side MOSFET. The APW8715A
• Operates from An Input Battery Voltage Range of steps down high voltage to generate low-voltage chipset
+2.7V to +28V
or RAM supplies in notebook computers.
• 20mA Low Dropout Regulator (LDO) with Fixed 5. The APW8715A provides excellent transient response and
3V Output
accurate DC voltage output in either PFM or PWM Mode.
• Power-On-Reset Monitoring on LDO pin
In Pulse Frequency Mode (PFM), the APW8715A provides
very high efficiency over light to heavy loads with loading-
• Excellent line and load transient responses
modulated switching frequencies. In PWM Mode, the con-
• PFM mode for increased light load efficiency
verter works nearly at constant frequency for low-noise
• Programmable PWM Frequency from 100kHz to requirements.
1000kHz
The APW8715A is equipped with accurate current-limit,
• Integrated 30mΩ at LDO=5V N-Channel MOSFET output under-voltage, and output over-voltage protections,
For High Side
perfect for various applications. A Power-On-Reset func-
• Integrated 12mΩ at LDO=5V N-Channel MOSFET tion monitors the voltage on VLDO to prevent wrong
For Low Side
operation during power-on. The APW8715A has external
• Integrated Bootstrap Forward P-CH MOSFET
adjustable soft-start and built-in an integrated output dis-
charge method for soft stop. A soft-start ramps up the
• External Adjustable Soft-Start and Soft-Stop
output voltage with programmable timing to reduce the
• Selectable Forced PWM or automatic PFM/PWM start-up current. A soft-stop function actively discharges
mode
the output capacitors.
• Power Good Monitoring
The APW8715A is available in TQFN4x4-23 (Power PAK).
• 70% Under-Voltage Protection
• 125% Over-Voltage Protection
• Current-Limit Protection
Applications
- Using Sense Low-Side MOSFET’s RDS(ON)
• Over-Temperature Protection
• TQFN-23 4mmx4mm package
• Lead Free and Green Device Available (RoHS
Compliant)
• Notebook
• Mother Board
• Table PC
• Hand-Held Portable
• AIO PC
• Set-top boxes
• LCD TV
ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and
advise customers to obtain the latest version of relevant information to verify before placing orders.
Copyright © ANPEC Electronics Corp.
Rev. A.1 - Aug., 2014
1
www.anpec.com.tw
1 page  
APW8715A
Electrical Characteristics
Unless otherwise specified, these specifications apply over VIN=12V,VEN=5V and TA= -40 to 85 oC. Typical values are at TA=25oC.
Symbol
Parameter
POWER-OK INDICATOR
VPOK
POK Threshold
IPOK POK Leakage Current
POK Sink Current
POK Out Debounce Time2
POK Enable Delay Time
CURRENT SENSE
IOCP OCP Threshold
Zero Crossing Comparator
Offset
PROTECTION
VUV UVP Threshold
UVP Debounce Interval
UVP Enable Delay
VOVR
OVP Rising Threshold1
OVP Propagation Delay
TOTR
OTP Rising Threshold (Note
5)
OTP Hysteresis (Note 5)
LDO OUTPUT
VLDO
LDO Output Voltage
Test Condition
POK in from Lower (POK Goes
High)
POK out from Normal (POK Goes
Low)
VPOK=5V
VPOK=0.5V
When run away 90%
From EN High to POK High
Valley Current of IL
VGND-LX Voltage, PFM=0V
EN high to UVP workable
OVP Occur
VFB Rising, Over Voltage=10mV
LDOIN=12V, No load
Min.
APW8715A
Typ. Max.
Unit
87 90 93 %
120 125 130 %
-
1.25
-
-
0.1
7.5
20
Tss
- µA
- mA
- µs
- ms
7 - -A
-5 0 5 mV
65 70 75 %
16 µs
Tss ms
120 125 130 %
- 3 - µs
- 145 - oC
- 45 - oC
- 5.3 - V
Copyright © ANPEC Electronics Corp.
Rev. A.1 - Aug., 2014
5
www.anpec.com.tw
5 Page 
APW8715A
Function Description
Constant-On-Time PWM Controller with Input Feed-
Forward
The constant on-time control architecture is a pseudo-
fixed frequency with input voltage feed-forward. This ar-
chitecture relies on the output filter capacitor’s effective
series resistance (ESR) to act as a current-sense resistor,
so the output ripple voltage provides the PWM ramp signal.
In PFM operation, the high-side switch on-time controlled
by the on-time generator is determined solely by a one-
shot whose pulse width is inversely proportional to input
voltage and directly proportional to output voltage. In PWM
operation, the high-side switch on-time is determined by
a switching frequency control circuit in the on-time gen-
erator block.
The switching frequency control circuit senses the switch-
ing frequency of the high-side switch and keeps regulat-
ing it at a constant frequency in PWM mode. The design
improves the frequency variation and is more outstand-
ing than a conventional constant on-time controller, which
has large switching frequency variation over input voltage,
output current and temperature. Both in PFM and PWM,
the on-time generator, which senses input voltage on
VIN pin, provides very fast on-time response to input line
transients.
Another one-shot sets a minimum off-time (typical:
250ns). The on-time one-shot is triggered if the error com-
parator is high, the low-side switch current is below the
current-limit threshold, and the minimum off-time one-
shot has timed out.
Over-Current Protection of the PWM Converter
In PFM mode, an automatic switchover to pulse-frequency
modulation (PFM) takes place at light loads. This
switchover is affected by a comparator that truncates the
low-side switch on-time at the inductor current zero
crossing. This mechanism causes the threshold between
PFM and PWM operation to coincide with the boundary
between continuous and discontinuous inductor-current
operation (also known as the critical conduction point).
The on-time of PFM is given by:
TON-PFM
=
1
FSW
×
VOUT
VIN
Where FSW is the nominal switching frequency of the
converter in PWM mode.
The load current at handoff from PFM to PWM mode is
given by:
ILOAD (PFM to PWM)
=
1
2
×
VIN
- VOUT
L
× TON-PFM
= VIN - VOUT × 1 × VOUT
2L FSW VIN
Forced-PWM Mode
The Forced-PWM mode disables the zero-crossing
comparator, which truncates the low-side switch on-time
at the inductor current zero crossing. This causes the
low-side gate-drive waveform to become the complement
of the high-side gate-drive waveform. This in turn causes
the inductor current to reverse at light loads while UG
maintains a duty factor of VOUT/VIN. The benefit of Forced-
PWM mode is to keep the switching frequency fairly
constant. The Forced-PWM mode is most useful for re-
ducing audio frequency noise, improving load-transient
response, and providing sink-current capability for dy-
namic output voltage adjustment.
When V is above the PFM high threshold (2.5V,
PFM
minimum), the converter is in forced-PWM mode. When
VPFM is below the PFM low threshold (0.5V, maximum),
the chip is in automatic PFM/PWM Mode.
Power-On-Reset
A Power-On-Reset (POR) function is designed to prevent
wrong logic controls when the LDO voltage is low. The
POR function continually monitors the bias supply volt-
age on the LDO pin if at least one of the enable pins is set
high. When the rising LDO voltage reaches the rising
POR voltage threshold (4.35V, typical), the POR signal
goes high and the chip initiates soft-start operations.
Should this voltage drop lower than 4.25V (typical), the
POR disables the chip.
En Pin Control
When V is above the EN high threshold (2.5V,
EN
minimum), the converter is enabled. When VEN is below
the EN low threshold (0.5V, maximum), the chip is in the
shutdown and only low leakage current is taken from
VCC.
Copyright © ANPEC Electronics Corp.
Rev. A.1 - Aug., 2014
11
www.anpec.com.tw
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet APW8715A.PDF ] | |
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