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Número de pieza | APW7120 | |
Descripción | Synchronous Buck PWM Controller | |
Fabricantes | ANPEC | |
Logotipo | ||
Hay una vista previa y un enlace de descarga de APW7120 (archivo pdf) en la parte inferior de esta página. Total 22 Páginas | ||
No Preview Available ! APW7120
5V to 12V Supply Voltage, 8-PIN, Synchronous Buck PWM Controller
Features
General Description
• Operating with Single 5~12V Supply Voltage
or Two Supply Voltages
• Drive Dual Low Cost N-Channel MOSFETs
- Adaptive Shoot-Through Protection
• Built-in Feedback Compensation
- Voltage-Mode PWM Control
- 0~100% Duty Ratio
- Fast Transient Response
• ±2% 0.8V Reference
- Over Line, Load Regulation, and Operating
Temperature
• Programmable Over-Current Protection
- Using R of Low-Side MOSFET
DS(ON)
• Hiccup-Mode Under-Voltage Protection
• 118% Over-Voltage Protection
• Adjustable Output Voltage
• Small Converter Size
- 300kHz Constant Switching Frequency
- Small SOP-8 Package
• Built-In Digital Soft-Start
• Shutdown Control Using an External MOSFET
• Lead Free and Green Devices Available
(RoHS Compliant)
Applications
The APW7120 is a fixed 300kHz frequency, voltage
mode, and synchronous PWM controller. The device
drives two low cost N-channel MOSFETs and is de-
signed to work with single 5~12V or two supply
voltage(s), providing excellent regulation for load
transients.
The APW7120 integrates controls, monitoring, and
protection functions into a single 8-pin package to
provide a low cost and perfect power solution.
A power-on-reset (POR) circuit monitors the VCC
supply voltage to prevent wrong logic controls. An
internal 0.8V reference provides low output voltage
down to 0.8V for further applications. An built-in digital
soft-start with fixed soft-start interval prevents the
output voltage from overshoot as well as limits the
input current. The controller’s over-current protection
monitors the output current by using the voltage drop
across the low-side MOSFET’s R , eliminating the
DS(ON)
need of a current sensing resistor. Additional under
voltage and over voltage protections monitor the
voltage on FB pin for short-circuit and over-voltage
protections. The over-current protection cycles the
soft-start function until 4 over-current events are
counted.
Pulling and holding the voltage on OCSET pin below
0.15V with an open drain device shuts down the
controller.
Pin Configuration
• Motherboard
• Graphics Card
• High Current, up to 20A, DC-DC Converters
BOOT 1
UGATE 2
GND 3
LGATE 4
8 PHASE
7 OCSET
6 FB
5 VCC
SOP-8
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.5 - Jun., 2008
1
www.anpec.com.tw
1 page APW7120
Function Pin Description
BOOT (Pin 1)
This pin provides ground referenced bias voltage to
the high-side MOSFET driver. A bootstrap circuit with
a diode connected to 5~12V is used to create a
voltage suitable to drive a logic-level N-channel
MOSFET.
UGATE (Pin 2)
Connect this pin to the high-side N-channel MOSFET’s
gate. This pin provides gate drive for the high-side
MOSFET.
GND (Pin 3)
The GND terminal provides return path for the IC’s bias
current and the low-side MOSFET driver’s pull-low
current. Connect the pin to the system ground via very
low impedance layout on PCBs.
LGATE (Pin 4)
Connect this pin to the low-side N-channel MOSFET’s
gate. This pin provides gate drive for the low-side
MOSFET.
where R1 is the resistor connected from VOUT to FB ,
and R2 is the resistor connected from FB to GND. The
FB pin is also monitored for under and over-voltage
events.
OCSET (Pin 7)
The OCSET is a dual-function input pin for over-
current protection and shutdown control. Connect a
resistor (R ) from this pin to the Drain of the low-
OCSET
side MOSFET. This resistor, an internal 40µA current
source (IOCSET), and the MOSFET’s on-resistance
(RDSON) set the converter over-current trip level (IPEAK)
according to the following formula:
IPEAK = 40μ A ⋅ ROCSET - 0.4V
R DSON
(A)
Pulling and holding this pin below 0.15V with an open
drain device, with very low parasitic capacitor, shuts
down the IC with floating output and also resets the
over-current counter. Releasing OCSET pin initiates a
new soft-start and the converter works again.
VCC (Pin 5)
PHASE (Pin 8)
Connect this pin to a 5~12V supply voltage. This pin
provides bias supply for the control circuitry and the
low-side MOSFET driver. The voltage at this pin is
monitored for the Power-On-Reset (POR) purpose.
The pin provides return path for the high-side MOSFET
driver’s pull-low current. Connect this pin to the high-
side MOSFET’s source.
FB (Pin 6)
This pin is the inverting input of the internalGm amplifier.
Connect this pin to the output (V ) of the converter
OUT
via an external resistor divider for closed-loop operation.
The output voltage set by the resistor divider is deter-
mined using the following formula :
V OUT = 0.8V ⋅ ( 1 + R1 )
R2
(V)
Copyright © ANPEC Electronics Corp.
Rev. A.5 - Jun., 2008
5
www.anpec.com.tw
5 Page APW7120
Operating Waveforms (Cont.)
(Refer to the typical application circuit, VBIAS=VIN=+12V supplied by an ATX Power Supply)
5. Over-Current Protection
No Connecting a shutdown MOSFET
at OCSET Pin
ROCSET=15k
APM2512
Connecting a shutdown MOSFET
(2N7002) at OCSET Pin
ROCSET=15k
APM2512
VOUT
VOUT
11
2 IL
Ch1 : VOUT, 1V/Div, DC
Time : 5ms/Div
Ch2 : IL, 10A/Div, DC
BW = 20 MHz
6. OCSET Voltage RC Delay
No Connecting a shutdown MOSFET
at OCSET Pin
VOCSET
IL
2 IL
Ch1 : VOUT, 1V/Div, DC Ch2 : IL, 10A/Div, DC
Time : 5ms/Div
BW = 20 MHz
Connecting a shutdown MOSFET
(2N7002) at OCSET Pin
VOCSET
IL
1,2
CProber=8pF
OCP
1,2 CProber=8pF
C2N7002=44pF (measured)
OCP
Ch1 : VOCSET, 0.5V/Div, DC Ch2 : IL, 10A/Div, DC
Time : 2µS/Div
BW = 20 MHz
Ch1 : VOCSET, 0.5V/Div, DC
Time : 2µ S/Div
Ch2 : IL, 10A/Div, DC
BW = 20 MHz
Copyright © ANPEC Electronics Corp.
Rev. A.5 - Jun., 2008
11
www.anpec.com.tw
11 Page |
Páginas | Total 22 Páginas | |
PDF Descargar | [ Datasheet APW7120.PDF ] |
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