G767 datasheet(11/14 Pages) GMT

11 / 14 page

Ver: 2.5

Dec 14, 2004

TEL: 886-3-5788833

http://www.gmt.com.tw

G767

Global Mixed-mode Technology Inc.

Table 7. Conversion-Rate Control Byte

DATA

CONVERSION RATE (Hz)

AVERAGE SUPPLY CURRENT (µA TYP, at Vcc = 3.3V)

00h

0.0625

01h

0.125

02h

0.25

03h

0.5

04h

05h

128

06h

225

07h

425

08h to FFh

RFU

Table 8. RLTS and RRTE Temp Register Update Timing Chart

OPERATING MODE

CONVERSION

INITIATED BY:

NEW CONVERSION RATE

(CHANGED VIA WRITE TO WCRW)

TIME UNTIL RLTS AND

RRTE ARE UPDATED

Auto-Convert

Power-on reset

N/A (0.25Hz)

156ms max

Auto-Convert

1-shot command, while idling be-

tween automatic conversions

N/A

156ms max

Auto-Convert

1-shot command that occurs dur-

ing a conversion

N/A

When current conversion is

complete (1-shot is ignored)

Auto-Convert

Rate timer

0.0625Hz

20sec

Auto-Convert

Rate timer

0.125Hz

10sec

Auto-Convert

Rate timer

0.25Hz

5sec

Auto-Convert

Rate timer

0.5Hz

2.5sec

Auto-Convert

Rate timer

1Hz

1.25sec

Auto-Convert

Rate timer

2Hz

625ms

Auto-Convert

Rate timer

4Hz

312.5ms

Auto-Convert

Rate timer

8Hz

237.5ms

Hardware Standby

STBY

N/A

156ms

Software Standby

RUN/STOP bit

N/A

156ms

Software Standby

1-shot command

N/A

156ms

To check for internal bus collisions, read the status

byte. If the least significant seven bits are ones, dis-

card the data and read the status byte again. The

status bits LHIGH, LLOW, RHIGH, and RLOW are

refreshed on the SMBus clock edge immediately fol-

lowing the stop condition, so there is no danger of los-

ing temperature-related status data as a result of an

internal bus collision. The OPEN status bit (diode con-

tinuity fault) is only refreshed at the beginning of a

conversion, so OPEN data is lost. The ALERT in-

terrupt latch is independent of the status byte register,

so no false alerts are generated by an internal bus

collision.

When auto-converting, if the THIGH and TLOW limits

are close together, it’s possible for both high-temp and

low-temp status bits to be set, depending on the

amount of time between status read operations (espe-

cially when converting at the fastest rate). In these

circumstances, it’s best not to rely on the status bits to

indicate reversals in long-term temperature changes

and instead use a current temperature reading to es-

tablish the trend direction.

Conversion Rate Byte

The conversion rate register (Table 7) programs the

time interval between conversions in free-running

auto-convert mode. This variable rate control reduces

the supply current in portable-equipment applications.

The conversion rate byte’s POR state is 02h (0.25Hz).

The G767 looks only at the 3 LSB bits of this register,

so the upper 5 bits are “don’t care” bits, which should

be set to zero. The conversion rate tolerance is

±25%

at any rate setting.

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