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FAN5234
Mobile-Friendly PWM/PFM Controller

Features
Wide input voltage range (2 to 24V) for Mobile systems Excellent dynamic response with Voltage Feed-Forward and Average Current Mode control Lossless current sensing on low-side MOSFET or precision over-current using sense resistor VCC Under-voltage Lockout Power-Good Signal Light load Hysteretic mode maximizes efficiency QSOP16, TSSOP16 300Khz or 600Khz operation

General Description
The FAN5234 PWM controller provides high efficiency and regulation with an adjustable output from 0.9V to 5.5V that are required to power I/O, chip-sets, memory banks or peripherals in high-performance notebook computers, PDAs and Internet appliances. Synchronous rectification and hysteretic operation at light loads contribute to a high efficiency over a wide range of loads. The hysteretic mode of operation can be disabled if PWM mode is desired for all load levels. Efficiency is even further enhanced by using MOSFET s RDS(ON) as a current sense component. Feed-forward ramp modulation, average current mode control, and internal feedback compensation provide fast response to load transients. The FAN5234 monitors these outputs and generates a PGOOD (power good) signal when the soft-start is completed and the output is within 10% of its set point. A built-in over-voltage protection prevents the output voltage from going above 120% of the set point. Normal operation is automatically restored when the overvoltag
e conditions go away. Under-voltage protection latches the chip off when the output drops below 75% of its set value after the soft-start sequence is completed. An adjustable over-current function monitors the output current by sensing the voltage drop across the lower MOSFET.

Applications
Mobile PC regulator Hand-Held PC power

Typical Application
VIN (BATTERY) 2 to 24V
1 VCC VIN BOOT

C1 D1 5 C5 L1 Q1B
10 9 12 LDRV PGND ISNS VSEN VOUT 15

C2

5 C4

11

FAN5234
R5
14 ILIM EN SS1 4 3 7 16 8 6 2 5 13 SW

Q1A
HDRV

1.8V 3.5A C6 R1

R3

C3 5 R4
FPWM AGND PGOOD

R2

Figure 1. 1.8V Output Regulator (see Table 2, page 12 for BOM)

REV. 1.0.10 5/3/04

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FAN5234 DATASHEET