SA56004GD datasheet(7/36 Pages) NXP

7 / 36 page

SA56004X_5

Product data sheet

Rev. 05 — 22 May 2008

7 of 36

NXP Semiconductors

SA56004X

Digital temperature sensor with overtemperature alarms

8. Local LOW setpoint (LLS) and Remote LOW temperature setpoints (RLSHB) at 0

°C.

9. Conversion Rate register (CR) is set to 8h; the default value of about 16

conversions/s.

7.5 Starting conversion

Upon POR, the RUN/STOP bit 6 of the conﬁguration register is zero (default condition),

then, the device will enter into its free-running operation mode in which the device A/D

converter is enabled and the measurement function is activated. In this mode, the device

cycles the measurements of the local and remote temperature automatically and

periodically. The conversion rate is deﬁned by the programmable conversion rate stored in

the conversion rate register. It also performs comparison between readings and limits of

the temperature in order to set the ﬂags and interruption accordingly at the end of every

conversion. Measured values are stored in the temp registers, results of the limit

comparisons are reﬂected by the status of the ﬂag bits in the status register and the

interruption is reﬂected by the logical level of the ALERT and T_CRIT output. If the

power-on temperature limit is not suitable, the temp limit values could be written into the

limit registers during the busy-conversion duration of about 38 ms of the ﬁrst conversion

after power-up. Otherwise, the status register must be read and the conﬁguration bit 7

must be reset in order to recover the device from interruption caused by the undesired

temp limits.

7.6 Low power software standby mode

The device can be placed in a software standby mode by setting the RUN/STOP bit 6 in

the conﬁguration register HIGH (logic 1). In standby, the free-running oscillator is stopped,

the supply current is less than 10

µA if there is no SMBus activity, all data in the registers

is retained. However, the SMBus is still active and reading and writing registers can still be

performed. A one-shot command will initiate a single conversion which has the same

effect as any conversion that occurs when the device is in its free-running mode. To

restore the device to free running mode, set the RUN/STOP bit 6 LOW (logic 0).

7.7 Temperature data format

The temperature data can only be read from the Local and Remote Temperature

registers; the setpoint registers (e.g., T_CRIT, LOW, HIGH) are read/write.

Both local and remote temperature reading data is represented by an 11-bit,

2’s complement word with the Least Signiﬁcant Bit (LSB) = 0.125

°C. The temperature

setpoint data for the remote channel is also represented by an 11-bit, 2’s complement

word with the LSB = 0.125

°C. The temperature setpoint data for both the local channel

and the T_CRIT setpoints are represented by 8-bit, 2’s complement words with the

LSB =1.0

°C. For 11-bit temp data, the data format is a left justiﬁed, 16-bit word available

in two 8-bit registers (high byte and low byte). For 8-bit temp data, the data is available in

a single 8-bit register (high byte only).

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