APW7057
High Power Step-Down Synchronous DC/DC Controller
Features
•
Operates from +5V Input
•
0.8V Internal Reference Voltage
- ±1.5% Accuracy Over Line, Load and Temp.
General Description
The APW7057 is a 300kHz constant frequency volt-
age mode synchronous switching controller that drives
external N-channel MOSFETs. When the input sup-
ply drops close to output, the upper MOSFET remains
on, achieving 100% duty cycle. Internal loop compen-
sation is optimized for fast transient response, elimi-
nating external compensation network. The precision
0.8V reference makes this part suitable for a wide va-
riety of low voltage applications. Soft start is internally
set to 2ms, limiting the input in-rush current and pre-
venting the output from overshoot during powering up.
The APW7057 has over current and short circuit
protections. Over current protection is achieved by
monitoring the voltage drop across the high side
MOSFET, eliminating the need for a current sens-
ing resistor and short circuit condition is detected
through the FB pin. If either fault conditions occur,
the APW7057 would initiate the soft start cycle. After
three cycles and if the fault condition persists, the
controller will be shut down. To restart the controller,
either recycle the V
CC
supply or momentarily pull the
OSCSET pin below 1.25V.
The APW7057 can be shutdown by pulling the OCSET
pin below 1.25V. In shutdown, both gate drive signals
will be low. The controller is available in a small SOP-
8 package.
•
0.8V to V
CC
Output Range
•
Full Duty Cycle Range
- 0% to 100%
•
Internal Loop Compensation
•
Internal Soft Start
- Typical 2ms
•
Programmable Over-Current Protection
- Lossless Sensing Using MOSFET R
DS (ON)
•
•
•
•
Under-Voltage Protection
Drives External N-Channel MOSFETs
Shutdown Control
Small SOP-8 Package
Applications
•
•
•
•
•
•
•
Motherboard
Graphics Cards
Cable or DSL Modems, Set Top Boxes
DSP Supplies
Memory Supplies
5V Input DC-DC Regulators
Distributed Power Supplies
Pinouts
BOOT
UGATE
GND
LGATE
1
2
3
4
8
7
6
5
PHASE
OCSET
FB
VCC
SOP-8 (Top View )
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.3 - Oct., 2003
1
www.anpec.com.tw
APW7057
Typical Application
R3
C3
1uF
5
2.2
V
IN
D1
1N4148
C1
1uF
+
+5V
C2
1000uF x2
R4
8.2k
C7
470pF
7
OCSET
VCC
BOOT
1
Q3
U G ATE
2
C4
0.1uF
Q1
L1
3.3uH
V
O UT
+2.5V/10A
C5
1000uF x2
Shutdown
8
P H AS E
6
U1
APW 7057
LG ATE
FB
GND
3
+
4
Q2
R1
5.1k
R2
2.4k
C6
0.1uF
Q1: APM2014N UC
Q2: APM2014N UC
Q3: APM2300A AC
C2: 1000uF/10V, ESR = 25m
Ω
C5: 1000uF/6.3V, ESR = 25m
Ω
.ECKH/
Figure 2.
Absolute Maximum Ratings
Symbol
V
CC
V
BOOT
Parameter
VCC Supply Voltage (VCC to GND)
BOOT Supply Voltage (BOOT to GND)
PHASE, OCSET to GND Input Voltage
FB to GND Input Voltage
Maxim um Junction Tem perature
T
STG
T
SDR
V
ESD
Storage Tem perature
Maxim um Soldering Tem perature, 10 Seconds
Minim um ESD Rating
Rating
-0.3 ~ 7
-0.3 ~ 15
-0.3 ~ 12
-0.3 ~ V
CC
+0.3
125
-65 ~ 150
300
±2
Unit
V
V
V
V
o
o
o
C
C
C
kV
Thermal Characteristics
Symbol
θ
JA
Parameter
Junction-to-Ambient Resistance in free air (SOP-8)
3
Value
160
Unit
o
C/W
Copyright
ANPEC Electronics Corp.
Rev. A.3 - Oct., 2003
www.anpec.com.tw
APW7057
Recommended Operating Conditions
Symbol
V
CC
V
OUT
V
IN
T
A
T
J
VCC Supply Voltage
Output Voltage of the Switching Regulator (Note)
Input Voltage of the Switching Regulator (Note)
Ambient Temperature
Junction Temperature
Parameter
Range
5
±
5%
0.8 ~ V
CC
3.3 ~ V
CC
0 ~ 70
0 ~ 125
Unit
V
V
V
o
o
C
C
Note : Refer to the typical application circuit
Electrical Characteristics
Unless otherwise specified, these specifications apply over V
CC
=5V, V
BOOT
=12V and T
A
= 0~70
o
C. Typical
values are at T
A
=25
o
C.
Symbol
Parameter
Test Conditions
APW7057
Min
Typ
Max
Unit
SUPPLY CURRENT
I
VCC
I
BOOT
VCC Nominal Supply
Current
BOOT Nominal Supply
Current
Rising VCC Threshold
Falling VCC Threshold
OSCILLATOR
F
OSC
Free Running Frequency
Ramp Upper Threshold
Ramp Lower Threshold
∆
V
OSC
V
REF
Ramp Amplitude
Reference Voltage
Reference Voltage
Accuracy
ERROR AMPLIFIER
DC Gain
F
P
F
Z
First Pole Frequency
First Zero Frequency
UGATE Duty Range
FB Input Current
Copyright
ANPEC Electronics Corp.
Rev. A.3 - Oct., 2003
4
UGATE and LGATE Open
UGATE Open
2.1
2.1
mA
mA
Under Voltage Lockout(UVLO)
4.0
3.8
250
4.2
4.0
300
2.85
0.95
1.9
0.8
-1.5
+1.5
4.4
4.2
340
V
V
kHz
V
V
V
P-P
V
%
REFERENCE VOLTAGE
75
10
1
0
100
0.1
dB
Hz
kHz
%
µ
A
www.anpec.com.tw
APW7057
Electrical Characteristics (Cont.)
Unless otherwise specified, these specifications apply over V
CC
=5V, V
BOOT
=12V and T
A
= 0~70
o
C. Typical
values are at T
A
=25
o
C.
Symbol
Parameter
Test Conditions
APW7057
Min
Typ
0.6
7.3
0.6
1.8
50
V
OCSET
=4.5V
FB falling
34
40
0.5
15
46
Max
Unit
PWM CONTROLLER GATE DRIVERS
UGATE Source
UGATE Sink
LGATE Source
LGATE Sink
T
D
I
OCSET
UV
FB
Dead Time
OCSET Sink Current
FB Under-Voltage Level
FB Under-Voltage
Hysteresis
SOFT-START AND SHUTDOWN
T
SS
Soft-Start Interval
Shutdown Threshold
OCSET Shutdown
Hysteresis
V
OCSET
Falling
2
1.25
20
mS
V
mV
PROTECTION
µA
V
mV
V
UAGTE
=1V
V
UGATE
=1V
V
LGATE
=1V
V
LGATE
=1V
A
Ω
A
Ω
nS
Functional Pin Description
BOOT (Pin 1)
This pin provides the supply voltage to the high side
MOSFET driver. A voltage no greater than 13V can
be connected to this pin as a supply to the driver.
For driving logic level N-channel MOSEFT, a boot-
strap circuit can be use to create a suitable driver’s
supply.
UGATE (Pin 2)
This pin provides gate drive for the high-side
MOSFET.
GND (Pin 3)
Signal and power ground for the IC. All voltage lev-
els are measured with respect to this pin. Tie this
pin to the ground plane through the lowest imped-
ance connection available.
Copyright
ANPEC Electronics Corp.
Rev. A.3 - Oct., 2003
5
www.anpec.com.tw
LGATE (Pin 4)
This pin provides the gate drive signal for the low
side MOSFET.
VCC (Pin 5)
This is the main bias supply for the controller and
its low side MOSFET driver. Must be closely
decoupled to GND (Pin 3).
DO NOT
apply a
voltage greater than 5.5V to this pin.
FB (Pin 6)
This pin is the inverting input of the error amplifier
and it receives the feedback voltage from an exter-
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