ADM1027ARQ 查看數據表（PDF） - ON Semiconductor

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ADM1027ARQ

dBCOOL™ Remote Thermal Controller and Voltage Monitor

ON Semiconductor 

ADM1027

5. Once the ADM1027 has responded to the alert response

address, the master must read the status registers and the

SMBALERT will only be cleared if the error condition has

gone away.

SMBus Timeout

The ADM1027 includes an SMBus timeout feature. If there is

no SMBus activity for a minimum of 15 ms and a maximum of

35 ms, the ADM1027 assumes that the bus is locked and releases

the bus. This prevents the device from locking or holding the

SMBus expecting data. Some SMBus controllers cannot handle

the SMBus timeout feature, so it can be disabled.

CONFIGURATION REGISTER 1 – Register 0x40

<6> TODIS = 0; SMBus timeout enabled (default)

<6> TODIS = 1; SMBus timeout disabled

VOLTAGE MEASUREMENT INPUTS

The ADM1027 has four external voltage measurement channels.

It can also measure its own supply voltage, VCC.

Pins 20 to 23 are dedicated to measuring 5 V, 12 V, 2.5 V supplies

and the processor core voltage VCCP (0 V to 3 V input). The

VCC supply voltage measurement is carried out through the VCC

pin (Pin 4). Setting Bit 7 of Configuration Register 1 (Reg. 0x40)

allows a 5 V supply to power the ADM1027 and be measured

without overranging the VCC measurement channel. The 2.5 V

input can be used to monitor a chipset supply voltage in com-

puter systems.

ANALOG-TO-DIGITAL CONVERTER

All analog inputs are multiplexed into the on-chip, successive

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

tion of 10 bits. The basic input range is 0 V to 2.25 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 ADC produces an output of 3/4 full scale

(768 decimal or 300 hex) for the nominal input voltage, and so

has adequate headroom to cope with overvoltages.

INPUT CIRCUITRY

The internal structure for the analog inputs is shown in Figure 12.

Each input circuit consists of an input protection diode, an

attenuator, and a capacitor to form a first order low-pass filter

that gives the input immunity to high frequency noise.

VOLTAGE MEASUREMENT REGISTERS

Reg. 0x20 2.5 V Reading = 0x00 default

Reg. 0x21 VCCP Reading = 0x00 default

Reg. 0x22 VCC Reading = 0x00 default

Reg. 0x23 5 V Reading = 0x00 default

Reg. 0x24 12 V Reading = 0x00 default

VOLTAGE MEASUREMENT LIMIT REGISTERS

Associated with each voltage measurement channel are high and

low limit registers. Exceeding the programmed high or low limit

causes the appropriate status bit to be set. Exceeding either limit

can also generate SMBALERT interrupts.

Reg. 0x44 2.5 V Low Limit = 0x00 default

Reg. 0x45 2.5 V High Limit = 0xFF default

Reg. 0x46 VCCP Low Limit = 0x00 default

Reg. 0x47 VCCP High Limit = 0xFF default

Reg. 0x48 VCC Low Limit = 0x00 default

Reg. 0x49 VCC High Limit = 0xFF default

Reg. 0x4A 5 V Low Limit = 0x00 default

Reg. 0x4B 5 V High Limit = 0xFF default

Reg. 0x4C 12 V Low Limit = 0x00 default

Reg. 0x4D 12 V High Limit = 0xFF default

12VIN

120k⍀

20k⍀

30pF

5VIN

93k⍀

47k⍀

30pF

3.3VIN

68k⍀

71k⍀

30pF

MUX

2.5VIN

45k⍀

94k⍀

30pF

VCCPIN

35k⍀

105k⍀

35pF

Figure 12. Structure of Analog Inputs

Table II shows the input ranges of the analog inputs and output

codes of the 10-bit A/D converter.

When the ADC is running, it samples and converts a voltage

input in 711 ms, and averages 16 conversions to reduce noise.

Therefore a measurement on any input takes nominally 11.38 ms.

REV. A

Rev. 3 | Page 11 of 56 | www.onsemi.com

–11–

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