F72820
F72820
Synchronous Buck PWM DC-DC Controller
Release Date: July, 2007
Version: V0.24P
Jul 2007
V0.24P
F72820
F72820 Datasheet Revision History
Version
0.21P
0.22P
0.23P
0.24P
Date
Mar/2005
Jun/2005
Mar/2006
Jul 2007
14
15
13
Page
Revision History
Preliminary version
Update application circuit
Correct application circuit
Update company address
Please note that all data and specifications are subject to change without notice. All the trade marks of products
and companies mentioned in this data sheet belong to their respective owners.
LIFE SUPPORT APPLICATIONS
These products are not designed for use in life support appliances, devices, or systems where malfunction of these
products can reasonably be expected to result in personal injury. Customers using or selling these products for
use in such applications do so at their own risk and agree to fully indemnify Fintek for any damages resulting from
such improper use or sales.
Jul 2007
V0.24P
F72820
Table of Content
1.
2.
3.
4.
5.
6.
General Description ..................................................................................................................... 1
Feature List .................................................................................................................................. 1
Pin Configuration ......................................................................................................................... 2
Block Diagram.............................................................................................................................. 2
Pin Description ............................................................................................................................. 3
Function Description .................................................................................................................... 4
6.1 Bootstrap Operation ................................................................................................................. 4
6.2 Dual Power Operation.............................................................................................................. 4
6.3 Soft-Start .................................................................................................................................. 5
6.4 Over-current Protection............................................................................................................ 5
6.5 Under-voltage Protection ......................................................................................................... 6
6.6 Output Voltage Selection.......................................................................................................... 7
6.7 Converter Shut Down............................................................................................................... 7
6.8 PWM Controller Feedback Compensation............................................................................... 7
6.9 Typical Characteristic ............................................................................................................... 9
7.
8.
9.
10.
Electrical Characteristic.............................................................................................................. 11
Ordering Information .................................................................................................................. 12
Package Dimensions (8-SOP/150 mil)....................................................................................... 13
Application Circuit ...................................................................................................................... 14
Jul 2007
V0.24P
F72820
1. General Description
The F72820 is a single PWM DC-DC converter controller for application requiring high current such as motherboard,
graphic card etc. The F72820 uses voltage mode PWM controller with fast transient response (driving two external
N-channel MOSFETs in a synchronous rectified buck converter topology) and integrates some functions such as
soft-start, over current and short circuit protections etc. Over current protection is achieved by monitoring the voltage
drops across the high side MOSFET without the need for a current sensing resistor and short circuit condition is
detected through FB pin. If fault conditions occur, the F72820 will initiate the soft start cycle. After three cycles and
the fault conditions persist, the controller will go into shut down status. In shut down status, both gate drive signals
will be low. To restart the controller, either recycling the Vcc supply or momentarily pulling OCSET pin below 1.25V.
The F72820 is available in 8-SOP package.
2. Feature List
Provides one synchronous rectified buck DC-DC PWM controller
Fast transient response (high bandwidth error amplifier; full 0~100% duty cycle)
Fixed operation frequency : 300KHz
Single loop voltage-mode control
Few external components
Output range adjustable down to 0.8V
Operation is under 5V input
Drives external N-channel MOSFETs
Over current monitor is used by MOSFET R
DS(ON)
0.8V internal reference voltage
±2% accuracy over line, load and temperature
Internal soft-start (typically 3 ms)
Internal loop compensation
Under voltage fault monitoring and protection
Over voltage protection
8-SOP package (150 mil)
F72820
-1-
Jul 2007
V0.24P
F72820
3. Pin Configuration
BOOT
UGATE
GND
LGATE
1
2
3
4
8
7
6
5
PHASE
OCSET
FB
VCC
F72820
4. Block Diagram
VCC
Regulator
BOOT
Reference
Voltage
Bias & SS
Power On
Reset
40uA
1.1V
OVP
OCSET
OCP
UVP
Control
Logic
PHASE
UGATE
Comp
VCC
0.5V
0.8V
Error
Amp
FB
GND
300KHz
Tri-OSC
LGATE
Figure 1:
Block Diagram
F72820
-2-
Jul 2007
V0.24P
