NE1617A_4

© NXP B.V. 2009. All rights reserved.

Product data sheet

Rev. 04 — 30 July 2009

8 of 27

NXP Semiconductors

NE1617A

Temperature monitor for microprocessor systems

8.3.1 Low power standby modes

Upon POR, the device is reset to its normal free-running auto-conversion operation mode.

The device can be put into standby mode by either using hardware control (connect the

STBY pin to LOW for hardware standby mode) or using software control (set bit 6 of the

configuration register to HIGH for software standby mode). When the device is put in

either one of the standby modes, the supply current is reduced to less than 10

µA if there

is no SMBus activity, all data in the device registers are retained and the SMBus interface

is still alive to bus communication. However, there is a difference in the device ADC

conversion operation between hardware standby and software standby modes. In

hardware standby mode, the device conversion is inhibited and the one-shot command

does not initiate a conversion. In software standby mode, the one-shot command will

initiate a conversion for both internal and external channels.

If a hardware standby command is received when the device is in normal mode and a

conversion is in progress, the conversion cycle will stop and data in reading temperature

registers will not be updated.

8.3.2 Configuration register

The configuration register is used to mask the Alert interrupt and/or to put the device in

software standby mode. Only two bits of this register (bit 6 and bit 7) are used as listed in

Table 5. Bit 7 is used to mask the device ALERT output from Alert interruption when this

bit is set to logic 1, and bit 6 is used to activate the standby software mode when this bit is

set to logic 1.

This register can be written or read using the commands of registers named WC and RC

accordingly. Upon Power-On Reset (POR), both bits are reset to zero.

8.3.3 External and internal temperature registers

Results of temperature measurements after every ADC conversion are stored in two

registers: Internal Temp register (RIT) for internal or local diode temperature, and External

Temp register (RET) for external or remote diode temperature. These registers can be

only read over the SMBus. The reading temperature data is in 2's complement binary form

consisting of 7-bit data and 1-bit sign (MSB), with each data count represents 1

°C, and

the MSB bit is transmitted first over the serial bus. The contents of those two registers are

updated upon completion of each ADC conversion. Table 6 shows some values of the

temperature and data.

Table 5.

Configuration register bit assignments

Bit

Symbol

POR state

Function

7 (MSB)

MASK

0

Mask ALERT interrupt. Interrupt is enabled when this bit

is LOW, and disabled when this bit is HIGH.

6

RUN/STOP

0

Standby or run mode control. When LOW, running mode

is enabled; when HIGH, standby mode is initiated.

5 to 0

-

n/a

reserved