BBUS Compliant Dual Temperature Monitor with Beta Compensation

Datasheet

SMSC EMC1212

9

Revision 1.1 (02-07-07)

DATASHEET

The external diode supported by the EMC1212 must be connected as shown in Figure 3.3. The

EMC1202 availabe from SMSC will support other diode configurations.

3.3

Resistance Error Correction

The EMC1212 includes resistance error correction implemented in the analog front end of the chip.

Resistance error correction is an automatic feature that eliminates the need to characterize and

compensate for the series resistance in the external diode lines.

When using a temperature sensor that does not include resistance error correction, voltage developed

across the parasitic resistance in the remote diode path produces an error in the reported temperature.

The error introduced by this resistance is approximately 0.7°C per ohm. Sources of series resistance

are PCB trace resistance, on die (i.e. on the processor) metal resistance, bulk resistance in the base

and emitter of the temperature transistor.

1

110 0000 1000

608h

63

111 1111 1000

7F8h

64

000 0000 0000

000h

65

000 0000 1000

008h

128

010 0000 0000

200h

191

011 1111 1000

3F8h

191.875

011 1111 1111

3FFh

Figure 3.3 External Diode Configuration

Table 3.1 EMC1212 Temperature Data Format (continued)

TEMPERATURE (°C)

2’S COMPLEMENT FORMAT

BINARY

HEX

Local Ground

to

DP

Typical remote

substrate transistor

i.e. CPU substrate PNP

to

DN