ADM1025ARQZ View Datasheet(PDF) - ON Semiconductor

Part Name

Description

Manufacturer

ADM1025ARQZ

Low Cost PC Hardware Monitor ASIC

ON Semiconductor 

Preliminary Technical Data

ADM1025/ADM1025A

Figure 12. Writing to the Address Pointer Register Only

Figure 13. Reading Data from a Previously Selected Register

When reading data from a register there are two possibilities:

1. If the ADM1025/ADM1025A’s Address Pointer Register

value is unknown or not the desired value, it is first

necessary to set it to the correct value before data can be

read from the desired data register. This is done by

performing a write to the ADM1025/ADM1025A as

before, but only the data byte containing the register

address is sent, since data should not be written to the

register. This is shown in Figure 12.

A read operation is then performed consisting of the serial

bus address, R/W bit set to 1, followed by the data byte

read from the data register. This is shown in Figure 13.

2. If the Address Pointer Register is known to be already at

the desired address, data can be read from the

corresponding data register without first writing to the

Address Pointer Register, so Figure 12 can be omitted.

NOTES

1. Although it is possible to read a data byte from a data

register without first writing to the Address Pointer

Register, if the Address Pointer Register is already at the

correct value, it is not possible to write data to a register

without writing to the Address Pointer Register because

the first data byte of a write is always written to the

Address Pointer Register.

2. In Figure 11 to Figure 13, the serial bus address is shown as

the default value 01011(A1)(A0), where A1 and A0 are set

by the three-state ADD pin.

4. If Reset or interrupt functionality is required, the address

pin cannot be strapped to GND, since this would keep the

ADD/RST/INT/NTO pin permanently low.

MEASUREMENT INPUTS

The ADM1025/ADM1025A has six external measurement

inputs, five for voltage and one (two pins) for temperature.

Internal measurements are also carried out on VCC and the on-

chip temperature sensor.

A/D CONVERTER

These inputs are multiplexed into the on-chip, successive-

approximation, analog-to-digital converter. This has a

resolution of eight bits. The basic input range is 0 V to 2.5 V, but

the inputs have built-in attenuators to allow measurement of

2.5 V, 3.3 V, 5 V, 12 V, and the processor core voltage VCCP

without any external components. To allow for the tolerance of

these supply voltages, the A/D converter produces an output of

¾ full scale (decimal 192) for the nominal input voltage and so

has adequate headroom to cope with overvoltages. Table 5

shows the input ranges of the analog inputs and output codes of

the A/D converter.

When the ADC is running, it samples and converts an input

every 11.6 ms, except for the external temperature (D+ and D−)

input. This has special input signal conditioning and is averaged

over 16 conversions to reduce noise; a measurement on this

input takes nominally 34.8 ms.

3. In addition to supporting the Send Byte and Receive Byte

protocols, the ADM1025/ADM1025A also supports the

Read Byte protocol (see System Management Bus

specifications Rev. 1.1 for more information).

Rev. P5 | Page 11 of 21| www.onsemi.com

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