FAN5250 Fairchild Semiconductor, FAN5250 Datasheet - Page 3

• Manufacturer Part Number: FAN5250
• Description: Mobile Processor Core-Voltage Regulator
• Manufacturer: Fairchild Semiconductor

Pin Description
REV. 1.1.6 3/12/03
Number Pin Name Pin Function Description
8–12
Pin
13
14
15
16
17
18
19
20
21
22
23
24
1
2
3
4
5
6
7
PGOOD
V
VID0–4
FPWM
AGND
PGND
FREQ
BOOT
HDRV
PVCC
LDRV
ALTV
ISNS
CORE
VCC
ILIM
VIN
SW
EN
SS
NC
+
Analog Ground . This is the signal ground reference for the IC. All voltage levels are
measured with respect to this pin.
VCC. This pin powers the chip. The IC starts to operate when voltage on this pin exceeds
4.6V (UVLO rising) and shuts down when it drops below 4.3V (UVLO falling).
Power Good Flag. An open-drain output that will pull LOW when the core output is
outside of a +25% –10% range of the VID reference voltage The PGOOD pin is kept high
during transitions between VID settings, Deep Sleep, and Reserved Mode transitions.
ENABLE. This pin enables IC operation when either left open, or pulled up to VCC.
Toggling EN will also reset the chip after a latched fault condition.
Forced PWM mode. When logic low, inhibits the chip from entering hysteretic operating
mode.
Alternative to VID. The IC will regulate to the voltage on this pin if it is below the highest
VID voltage (1.75V). Such a requirement may occur during CPU initialization or during
some power saving modes. This pin has a 10 µ A current source, so that its voltage can be
programmed with a resistor to GND. See Alternative Voltage Programming on page 8 for
details.
Frequency Set. Logic Low sets the operating frequency to 300Khz. High sets the
frequency to 600Khz.
Voltage Identification Code . Input to VID DAC. Sets the output voltage according to the
codes set as defined in Table 1.
Input Voltage from battery. This voltage is used by the oscillator for feed-forward
compensation of input voltage variation.
Soft Start. A capacitor from this pin to GND programs the slew rate of the converter
during initialization as well as in operation. This pin is used as the reference against which
the output is compared. During initialization, this pin is charged with a 25 µ A current
source. Once this pin reaches 0.5V, its function changes, and it assumes the value of the
voltage as set by the VID programming. The current driving this pin is then limited to
+500 µ A, that together with C
Current Limit. A resistor from this pin to GND sets the current limit.
VCORE Output Sense. This pin is the feedback from the VCORE output. Used for
regulation as well as PGOOD, under-voltage and over-voltage protection and monitoring.
No internal connection. While no connection is necessary, tying this pin to GND is
recommended to reduce coupled noise into pin 16 from pin 18.
BOOT. The positive supply for the upper MOSFET driver. Connect as shown in Figure 1.
High-Side Drive. The high-side (upper) MOSFET driver output.
Switching node. The return for the high-side MOSFET driver.
Current Sense Input. Monitors the voltage drop across the lower MOSFET or external
sense resistor for current feedback.
Power Ground. The return for the low-side MOSFET driver.
Low-Side Drive. The low-side (lower) MOSFET driver output.
Power VCC. The positive supply for the lower MOSFET driver.
SS
sets a controlled slew rate for VID code changes.
FAN5250
3