4

Rev. 1.4

07/24/01

IRU3021M

This pin controls the gate of an external MOSFET for the AGP linear regulator.

Leaving this pin open provides fixed output voltages of the 1.5V and 1.8V for the #3 and #4

linear regulators. When this pin is grounded the reference to the linear regulators are set

to 1.26V and therefore the output of the regulators can be programmed to any voltages

above the 1.26V using: Vout=1.26 × (1 + Rtop/Rbot)

Where:

Rtop = Top resistor connected from the output to the Vsense pin

Rbot = Bottom resistor connected from the Vsense pin to ground

This pin selects a range of output voltages for the DAC. When in the LOW state the range

is 1.3V to 2.05V and when it switches to HI state the range is 2.0V to 3.5V. This pin is TTL

compatible that realizes a logic “1” as either HI or Open. When left open, this pin is pulled

up internally by a 27KΩ resistor to 5V supply.

MSB input to the DAC that programs the output voltage. This pin is TTL compatible that

realizes a logic “1” as either HI or Open. When left open, this pin is pulled up internally by

a 27KΩ resistor to 5V supply.

Input to the DAC that programs the output voltage. This pin is TTL compatible that realizes

a logic “1” as either HI or Open. When left open, this pin is pulled up internally by a 27KΩ

resistor to 5V supply.

Input to the DAC that programs the output voltage. This pin is TTL compatible that realizes

a logic “1” as either HI or Open. When left open, this pin is pulled up internally by a 27KΩ

resistor to 5V supply.

LSB input to the DAC that programs the output voltage. This pin is TTL compatible that

realizes a logic “1” as either HI or Open. When left open, this pin is pulled up internally by

a 27KΩ resistor to 5V supply.

This pin is an open collector output that switches LO when any of the outputs are outside

of the specified under-voltage trip point. It also switches low when Vsen1 pin is more than

10% above the DAC voltage setting.

PIN DESCRIPTIONS

D4

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

D3

1

1

1

1

1

1

1

1

0

0

0

0

0

0

0

0

D2

1

1

1

1

0

0

0

0

1

1

1

1

0

0

0

0

D1

1

1

0

0

1

1

0

0

1

1

0

0

1

1

0

0

D0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

Vs

1.30

1.35

1.40

1.45

1.50

1.55

1.60

1.65

1.70

1.75

1.80

1.85

1.90

1.95

2.00

2.05

D4

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

D3

1

1

1

1

1

1

1

1

0

0

0

0

0

0

0

0

D2

1

1

1

1

0

0

0

0

1

1

1

1

0

0

0

0

D1

1

1

0

0

1

1

0

0

1

1

0

0

1

1

0

0

D0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

Vs

2.0

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3.0

3.1

3.2

3.3

3.4

3.5

Table 1 - Set point voltage vs. VID codes.

PIN# PIN SYMBOL

PIN DESCRIPTION

1

2

3

4

5

6

7

8

Drive2

Fix

VID4

VID3

VID2

VID1

VID0

PGood