6

SMBus Thermal Sensor with External Diode Input

TCM1617

TCM1617-1

2/5/99

 2001 Microchip Technology Inc.

DS21485A

Standby Mode Operation

STBY#

Chip Stop Bit

One Shot?

Operating Mode

0

Don’t Care

Don’t Care

Standby

1

0

Don’t Care

Normal

1

1

No

Standby

1

1

Yes

Normal

(1 Conversion Only,

then Standby)

remains active, and all registers may be read from and

written to normally. The INT_TEMP and EXT_TEMP regis-

ters will contain whatever data was valid at the time of

Standby. (Transitions on SDA or SCL due to external bus

activity may increase the Standby power consumption.)

D+

Bi-directional. this pin connects to the anode of the

external diode and is the positive A/D input. Current is

injected into the external diode from the TCM1617, and the

digital temperature data.

D–

Bi-directional. This pin connects to the cathode of the

external diode. Current is sunk from the external diode into

the TCM1617 through this pin. It also is the negative input

terminal to the TCM1617’s A/D converter. This node is kept

at approximately 0.7V above GROUND.

Input. Power supply input. See electrical specifications.

GND

Input. Ground return for all TCM1617 functions.

FUNCTIONAL DESCRIPTION

The TCM1617 acquires and converts temperature infor-

mation from two separate sources, both silicon junction

diodes, with a basic accuracy of

±1°C. One is located on the

TCM1617 die; the other is connected externally. The exter-

nal diode may be located on another IC die. The analog-to-

digital converter on the TCM1617 alternately converts tem-

perature data from the two sensors and stores them sepa-

rately in internal registers.

The system interface is a slave SMBus port with an

ALERT# (SMBALERT#) interrupt output. The interrupt is

triggered when one or more of four preset temperature

thresholds are tripped (see Figure 1). These four thresholds

are user-programmable via the SMBus port. Additionally,

the temperature data can be read at any time through the

SMBus port. Nine SMBus addresses are programmable for

the TCM1617, which allows for a multi-sensor configuration.

Also, there is low-power Standby mode where temperature

acquisition is suspended.

STANDBY MODE

The TC1617 allows the host to put it into a low power

A/D converter is halted, and the temperature data registers

are frozen. The SMBus port operates normally. Standby

mode can be enabled with either the STBY# input pin or the

CHIP STOP bit in the CONFIG register. The following table

summarizes this operation.

Figure 1. Temperature-vs-Setpoint Event Generation

SMBUS SLAVE ADDRESS

The two pins ADD1 and ADD0 are tri-state input pins

which determine the 7-Bit SMBus slave address of the

TCM1617. The address is latched during POR.

SERIAL PORT OPERATION

Time

EXT_HLIM

INT_HLIM

EXT_LLIM

INT_LLIM

EXT_TEMP

INT_TEMP

ASSERT

ALERT#

ALERT#

ASSERT

ALERT#

ASSERT

ALERT#

ASSERT

ALERT#

Note: This diagram inplies that the appropriate setpoint is moved, temporarily, after each ALERT#

event to suppress re-assertion of ALERT# immediately after the ARA/de-assertion.