Philips Semiconductors

Product data sheet

SA56004X

±1 °C accurate, SMBus-compatible, 8-pin, remote/local

digital temperature sensor with over temperature alarms

2004 Oct 06

16

T_CRIT output

The T_CRIT output is LOW when any temperature reading is

greater than the preset limit in the corresponding critical temperature

setpoint register. When one of the T_CRIT setpoint temperatures is

exceeded, the appropriate status register bit, 1 (RCRIT) or 0

(LCRIT), is set.

After every local and remote temperature conversion the Status

register flags and the T_CRIT output are updated. Figure 15 is a

timing diagram showing the relationship of T_CRIT output, Status

bit 1 (RCRIT) and the remote critical temperature setpoint (RCS),

and critical temperature hysteresis (TH) with remote temperature

changes. Note that the T_CRIT output is de-activated only after the

remote temperature is below the remote temperature setpoint, RCS

minus the Hysteresis, TH. In the interrupt mode only, the Status

register flags are reset after the Status register is read.

RCS

RCS - TH

Status Bit 1, RCRIT

T_CRIT Output

Remote Temperature

A

BC

SL02058

Figure 15. T_CRIT temperature response timing diagram

Event A: T_CRIT goes LOW and Status bit 1, RCRIT is set HIGH

when Remote Temperature exceeds RCS, Remote T_CRIT

Setpoint.

Event B: Remote Temperature goes below RCS-TH. T_CRIT is

deactivated, but Status Register remains unchanged.

Event C: The Status Register Bit 1, RCRIT is reset by a read of the

Status Register (in the interrupt mode).

Fault Queue

To suppress erroneous ALERT or T_CRIT triggering, the SA56004X

implements a Fault Queue for both local and remote channel. The

Fault Queue insures a temperature measurement is genuinely

beyond a HIGH, LOW or T_CRIT setpoint by not triggering until

three consecutive out-of-limit measurements have been made. The

fault queue defaults off upon POR and may be activated by setting

bit 0 in the Configuration register (address 09h) to ‘1’.

Remote HIGH

Setpoint

Remote LOW

Setpoint

RCS

ALERT Output

RCS -TH

Remote

Temperature

T_CRIT Output

AB

C

DE

F

G

H

Events

I

SL02059

NOTE: All events indicate the completion of a conversion.

Figure 16. Fault Queue Remote High and Low and T_CRIT,

T_CRIT Hysteresis setpoint response (Comparator mode)

At Event A: The remote temperature has exceeded the Remote

HIGH setpoint.

At Event B: Three consecutive over limit measurements have been

made exceeding the Remote HIGH setpoint; the ALERT output is

activated (goes LOW).

By now, the remote temp has exceeded the Remote T_CRIT

setpoint (RCS).

At Event C: Three consecutive over limit measurements have been

made exceeding RCS; the T_CRIT output is activated (goes LOW).

At Event D: The remote temperature falls below the RCS–TH

setpoint.

At Event E: The ALERT output is de-activated (goes HIGH) after a

below_high_limit temperature measurement is completed.

At Event F: Three consecutive measurements have been made

with the remote temperature below the RCS–TH threshold; the

T_CRIT output is de-activated (goes HIGH).

At Event G: The remote temp falls below the Remote LOW setpoint.

At Event H: Three consecutive measurements are made with the

temp below the Remote LOW setpoint; ALERT output is activated

(goes LOW).

At Event I: The ALERT output is de-activated (goes HIGH) after a

above_low_limit temperature measurement is completed.