APW7068_09 Datasheet, PDF (1/26 Pages) Anpec Electronics Coropration – Synchronous Buck PWM and Linear Controller with 0.8V Reference Out Voltage

APW7068
Synchronous Buck PWM and Linear Controller
with 0.8V Reference Out Voltage
Features
General Description
• Two Regulated Voltages and REF_OUT
- Synchronous Buck Converter
- Linear Regulator
- REF_OUT = 0.8V±1% with 3mA Source Current
• Single 12V Power Supply Required
• Excellent Both Output Voltage Regulation
- 0.8V Internal Reference
- ±1% Over Line Voltage and Temperature
• Integrated Soft-Start for PWM and Linear Outputs
• 300KHz Fixed Switching Frequency
• Voltage Mode PWM Control Design and Up to 89%
(Typ.) Duty Cycle
• Under-Voltage Protection Monitoring Linear Out-
put
• Over-Voltage Protection Monitoring PWM Output
• Over-Current Protection for PWM Output
- Sense Low-side MOSFET’s R_DS(ON)
• SOP-14, SSOP-16 and Compact QFN4x4-16 pack-
ages
• Lead Free and Green Devices Available
(RoHS Compliant)
Applications
• Graphic Cards
Simplified Application Circuit
12V
V_IN2
Q3
V_OUT2
Linear ^PWM
Controller ^Controller
V_IN1
Q1
L ^VOUT1
Q2
The APW7068 integrates synchronous buck PWM, linear
controller, and 0.8V Reference Out Voltage, as well as
the monitoring and protection functions into a single
package. The fixed 300kHz switching frequency synchro-
nous PWM controller drives dual N-channel MOSFETs,
which provides one controlled power output with over-
voltage and over-current protections. Linear controller
drives an external N-channel MOSFET with under-volt-
age protection.
The APW7068 provides excellent regulation for output load
variation. An internal 0.8V temperature-compensated ref-
erence voltage is designed to meet the requirement of
low output voltage applications.
The APW7068 with excellent protection functions: POR,
OCP, OVP and UVP. The Power-On-Reset (POR) circuit
can monitor V supply voltage exceeds its threshold
CC12
voltage while the controller is running, and a built-in digi-
tal soft-start provides both outputs with controlled rising
voltage. The Over-Current Protection (OCP) monitors the
output current by using the voltage drop across the lower
MOSFET’s R , comparing with the voltage of OCSET
DS(ON)
pin, V The maximum V voltage is limited to the
OCSET.
OCSET
internal default value 0.25V. In addition, when OCSET pin
is floating (no R_OCSET resistor), the over current threshold
will also be internal default value, 0.25V. When the output
current reaches the trip point, the controller will shutdown
the IC directly, and latch the converter’s output. The Un-
der-Voltage Protection (UVP) monitors the voltage of FBL
pin for short-circuit protection. When the V_FBL is less than
50% of V_REF, the controller will shutdown the IC directly.
The Over-Voltage Protection (OVP) monitors the voltage
of FB. When the V_FB is over 135% of V_REF, the controller will
make Low-side gate signal fully turn on until the fault
events are removed.
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.
1
Rev. A.6 - Aug., 2009
www.anpec.com.tw