W83321G Nuvoton Technology Corporation of America, W83321G Datasheet - Page 7

• Manufacturer Part Number: W83321G
• Description: IC BUCK SYNC ADJ 8SOIC
• Manufacturer: Nuvoton Technology Corporation of America
• Type: Step-Down (Buck)r

Specifications of W83321G

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.8 ~ 5 V
• Frequency - Switching: 250kHz
• Voltage - Input: 5V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -

6. INTERNAL BLOCK DIAGRAM
MOSFET Gate Drivers
Power for the high-side driver is through the BOOT pin. This voltage can be supplied by a separate,
higher voltage source, or supplied from a local charge pump structure or even the combination of the
two.
Since the voltage of the low-side MOSFET gate and the high-side MOSFET gate are being monitored
to determine the state of the MOSFET, it should be considered carefully to add external components
between the gate drivers and their respective MOSFET gates. Doing so may interfere with the shoot-
through protection.
Current Limit (Over current protection)
Current limit is realized by sensing the voltage across the low-side MOSFET while it is on. This
method enhances the converter's effeciency and reduces cost by eliminating a current sensing
resistor.
While low-side MOSFET is turned on, a constant current of 90uA is forced through R
external resistor connected between phase and ISEN, causing a fixed voltage drop. This fixed voltage
is compared against V
limit mode both the high-side and low-side MOSFETS are turned off. After a 25ms delay, a soft-start
COMP
FB
V
0.8V
REF
+
-
EA
Oscillator
250KHz
DS
and if the latter is higher, the chip enters current limit mode. In the current
Output
Clamp
Soft Start
Generator
Ramp
Ramp
- 7 -
Control
Logic
1.
5Vp
Publication Release Date: January, 2006
+
-
W83321S/W83321G
-p
POR
VDD
Control
Logic
Gate
90µA
OCSET
VDD
GND
Revision 0.51
which is an
LGATE
BOOT
UGATE
I
SEN