Remote High Limit

RDTS Measurement

TIME

ALERT mask set in

response to ARA

from master

LM99 ALERT Pin

Status Register: RTDS High

LM99

www.ti.com

SNIS129D – JANUARY 2003 – REVISED MARCH 2013

Bit D0 (the ALERT configure bit) in the FILTER and ALERT CONFIGURE REGISTER (xBF) must be set low in

order for the LM99 to respond to the ARA command.

The ALERT output can be disabled by setting the ALERT mask bit, D7, of the Configuration register. The power

on default is to have the ALERT mask bit and the ALERT configure bit low.

Figure 7. ALERT Output as an SMBus ALERT Temperature Response Diagram

T_CRIT_A OUTPUT and T_CRIT LIMIT

T_CRIT_A is activated when any temperature reading is greater than the limit preset in the critical temperature

setpoint register (T_CRIT), as shown in Figure 8. The Status Register can be read to determine which event

caused the alarm. A bit in the Status Register is set high to indicate which temperature reading exceeded the

T_CRIT setpoint temperature and caused the alarm, see STATUS REGISTER (SR).

Local and remote temperature diodes are sampled in sequence by the A/D converter. The T_CRIT_A output and

the Status Register flags are updated after every Local and Remote temperature conversion. T_CRIT_A follows

the state of the comparison, it is reset when the temperature falls below the setpoint RCS-TH. The Status

Register flags are reset only after the Status Register is read and if a temperature conversion(s) is/are below the

T_CRIT setpoint, as shown in STATUS REGISTER (SR).

Figure 8. T_CRIT_A Temperature Response Diagram

POWER ON RESET DEFAULT STATES

LM99 always powers up to these known default states. The LM99 remains in these states until after the first

conversion.

1. Command Register set to 00h

2. Local Temperature set to 0°C

3. Remote Diode Temperature set to 0°C until the end of the first conversion.

4. Status Register set to 00h.

5. Configuration register set to 00h; ALERT enabled, Remote T_CRIT alarm enabled and Local T_CRIT alarm

enabled

6. 85°C Local T_CRIT temperature setpoint

7. 110°C Remote T_CRIT temperature setpoint (126°C Remote diode junction temperature)

Copyright © 2003–2013, Texas Instruments Incorporated

Submit Documentation Feedback

11

Product Folder Links: LM99