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PDF APW7065A Data sheet ( Hoja de datos )
| Número de pieza | APW7065A | |
| Descripción | Synchronous Buck PWM Controller | |
| Fabricantes | Anpec Electronics Coropration | |
| Logotipo |  |
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APW7065A
Synchronous Buck PWM Controller
Features
General Description
• Single 12V Power Supply Required
• Fast Transient Response
- 0~90% Duty Ratio
• 0.8V Reference with 1% Accuracy
• Shutdown Function by Controlling COMP
The APW7065A uses fixed 300kHz switching frequency,
voltage mode, synchronous PWM controller which drives
dual N-channel MOSFETs. The device integrates the
control, monitoring and protection functions into a
single package, provides one controlled power output
with under-voltage and over-current protections.
Pin Voltage
• Internal Soft-Start (1.7ms) Function
• Voltage Mode PWM Control Design
• Under-Voltage Protection
• Over-Current Protection
- Sense Low Side MOSFET’s R
DS(ON)
• 300KHz Fixed Switching Frequency
• SOP-8P Package
• Lead Free and Green Devices Available
(RoHS Compliant)
Simplified Application Circuit
12V
VIN
The APW7065A provides excellent regulation for out-
put load variation. The internal 0.8V temperature-com-
pensated reference voltage is designed to meet the re-
quirement of low output voltage applications. An built-in
digital soft-start with fixed soft-start interval prevents the
output voltage from overshoot as well as limiting the in-
put current.
The APW7065A with excellent protection functions:
POR, OCP and UVP. The Power-On-Reset (POR) cir-
cuit can monitor VCC supply voltage exceeds its thresh-
old voltage while the controller is running, and a built-in
digital soft-start provides output with controlled voltage
rise. The Over-Current Protection (OCP) monitors the
output current by using the voltage drop across the lower
MOSFET’s RDS(ON), comparing with internal VOCP (0.29V),
when the output current reaches the trip point, the IC
APW7065A
shuts off the converter and initiates a new soft-start
L VOUT process. After two over-current events are counted,
the device turns off both high-side and low-side
MOSFETs and the converter's output is latched to be
floating. It requires a POR of VCC to restart. The Under-
Voltage Protection (UVP) monitors the voltage of FB pin
Pin Configuration
BOOT 1
8 PHASE
for short-circuit protection, when the VFB is less than
50% of VREF (0.4V), the controller will shutdown the IC
directly.
UGATE 2
7 COMP
GND 3
LGATE 4
6 FB
5 VCC
Applications
SOP-8P
(APW7065A)
• Graphics Card
• Mother Board
Thermal Pad
(Connect to GND Plane for better heat dissipation)
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.4 - Mar., 2008
1
www.anpec.com.tw
1 page  
APW7065A
Typical Operating Characteristics
Switching Frequency vs. Junction Temperature
310
305 VCC=12V
300
295
290
285
280
275
-40 -20 0 20 40 60 80 100 120
Junction Temperature (°C )
UGATE Source Current vs. UGATE Voltage
3.5
3
VBOOT=12V
2.5
2
1.5
1
0.5
0
0 2 4 6 8 10 12
UGATE Voltage (V)
LGATE Source Current vs. LGATE Voltage
6
5 VCC=12V
4
3
2
1
0
0 2 4 6 8 10 12
LGATE Voltage (V)
Reference Voltage vs. Junction Temperature
0.804
0.802
VCC=12V
0.8
0.798
0.796
0.794
0.792
-40 -20 0 20 40 60 80 100 120
Junction Temperature (°C )
UGATE Sink Current vs. UGATE Voltage
3
2.5 VBOOT=12V
2
1.5
1
0.5
0
0 2 4 6 8 10 12
UGATE Voltage (V)
LGATE Sink Current vs. LGATE Voltage
3.5
3
2.5
2 VCC=12V
1.5
1
0.5
0
0 2 4 6 8 10 12
LGATE Voltage (V)
Copyright © ANPEC Electronics Corp.
Rev. A.4 - Mar., 2008
5
www.anpec.com.tw
5 Page 
APW7065A
Function Description
Power-On-Reset (POR)
The Power-On-Reset (POR) function of APW7065A con-
tinually monitors the input supply voltage (V ) and the
CC
COMP pin. The supply voltage (V ) must exceed its ris-
CC
ing POR threshold voltage. The POR function initiates
soft-start operation after VCC and COMP voltages exceed
their POR thresholds. For operation with a single +12V
power source, VIN and VCC are equivalent and the +12V
power source must exceed the rising VCC threshold. The
POR function inhibits operation at disabled status (V
COMP
is less than 1.2V). With both input supplies above their
POR thresholds, the device initiates a soft-start interval.
Soft-Start
Voltage(V)
FB
12.5mV
8/Fosc
Time
Figure 2. The Controlled Stepped FB Voltage
during Soft Start
The APW7065A has a built-in digital soft-start to control
the output voltage rise and limit the current surge during
the start-up. In Figure 1, when VCC exceeds rising POR
threshold voltage, the delay time is counted from t1 to t2
and then soft-start will be enabled. During soft-start, an
internal ramp connected to the one of the positive inputs
of the Gm amplifier rises up from 0V to 2V to replace the
reference voltage (0.8V) until the ramp voltage reaches
the reference voltage. The soft-start interval is decided by
the oscillator frequency (300KHz). The formulation is given
by:
Tsoft−start = t3 − t2 = 512/FOSC = 1.7ms
Figure 2. shows more details of the FB voltage ramp. The
FB voltage soft-start ramp is formed with many small
steps of voltage. The voltage of one step is about 12.5mV in
FB, and the period of one step is about 8/F . This method
OSC
provides a controlled voltage rise and prevents the large
peak current to charge output capacitor.
Over-Current Protection
The over-current protection monitors the output current
by using the voltage drop across the lower MOSFET’s
RDS(ON) and this voltage drop will be compared with the
internal 0.29V reference voltage. If the voltage drop across
the lower MOSFET’s RDS(ON) is larger than 0.29V, an
over-current condition is detected. The IC shuts off the
converter and initiates a new soft-start process. After two
over-current events are counted, the device turns off both
high-side and low-side MOSFETs and the converter's
output is latched to be floating. It requires a POR of VCC
to restart. The threshold of the over current limit is given
by:
ILimit
=
0.29
RDS(ON)
For the over-current is never occurred in the normal oper-
ating load range; the variation of all parameters in the
above equation should be determined.
Voltage (V)
VCC
VOUT
- The MOSFET’s R is varied by temperature and
DS(ON)
gate to source voltage, the user should determine
the maximum RDS(ON) in manufacturer’s datasheet.
- The minimum Vocset should be used in the above
equation.
- Note that the ILIMIT is the current flow through the lower
MOSFET; I must be greater than maximum output
LIMIT
current and add the half of inductor ripple current.
t1 t2 t3
Figure 1. Soft Start Interval
Time
Copyright © ANPEC Electronics Corp.
Rev. A.4 - Mar., 2008
11
www.anpec.com.tw
11 Page | ||
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| PDF Descargar | [ Datasheet APW7065A.PDF ] | |
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