Rainbow-electronics MAX1718 Bedienungsanleitung PDF herunterladen (Seite 19)

MAX1718

Notebook CPU Step-Down Controller for Intel

Mobile Voltage Positioning (IMVP

II)

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On the rising edge of ZMODE, during power-up with

ZMODE high or on the falling edge of SUS when

ZMODE is high, the impedances at D0–D4 are sampled

by the impedance decoder to see if a large resistance

is in series with the pin. This is called Impedance

mode. If the voltage level on the pin is a logic low, an

internal switch connects the pin to an internal 26kΩ

pullup for about 4µs to see if the pin voltage can be

forced high (Figure 10). If the pin voltage can be pulled

to a logic high, the impedance is considered high and

so is the Impedance mode logic state. Similarly, if the

voltage level on the pin is a logic high, an internal

switch connects the pin to an internal 8kΩ pulldown to

see if the pin voltage can be forced low. If so, the pin is

high impedance and its Impedance mode logic state is

high. In either sampling condition, if the pin’s logic level

does not change, the pin is determined to be low

impedance and the Impedance mode logic state is low.

A high pin impedance (and logic high) is 100kΩ or

greater, and a low impedance (and logic low) is 1kΩ or

less. The Electrical Characteristics table guaranteed

levels for these impedances are 95kΩ and 1.05kΩ to

allow the use of standard 100kΩ and 1kΩ resistors with

5% tolerance.

Using the ZMODE Mux

There are many ways to use the versatile ZMODE mux.

The preferred method will depend on when and how

the VID DAC codes for the various states are deter-

mined. If the output voltage codes are fixed at PC

board design time, program both codes with a simple

combination of pin-strap connections and series resis-

tors (Figure 11). If the output voltage codes are chosen

during PC board assembly, both codes can be inde-

pendently programmed with resistors (Figure 12). This

matrix of 10 resistor-footprints can be programmed to

all possible Logic mode and Impedance mode code

combinations with only 5 resistors.

Often the CPU pins provide one set of codes that are

typically used with pullup resistors to provide the Logic

mode VID code, and resistors in series with D0–D4 set

the Impedance mode code. Since some of the CPU’s

VID pins may float, the open-circuit pins can present a

problem for the ZMODE mux’s Impedance mode. For

the Impedance mode to work, any pins intended to be

S1 S0 OUTPUT VOLTAGE (V)

GND GND 0.975

GND REF 0.950

GND OPEN 0.925

GND V

0.900

REF GND 0.875

REF REF 0.850

REF OPEN 0.825

REF V

0.800

OPEN GND 0.775

OPEN REF 0.750

OPEN OPEN 0.725

OPEN V

0.700

GND 0.675

REF 0.650

OPEN 0.625

0.600

Table 4. Suspend Mode DAC Codes

ZMODE

POR

ZMODE MUX

S0/S1

DECODER

SEL

OUT

IMPEDANCE

DECODER

SUS MUX

SEL

OUT

DAC

SUS

Figure 9. Internal Multiplexers Functional Diagram

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 34 35

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