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Table 7. conversion-rate control byte – Rainbow Electronics MAX6659 User Manual

Page 14

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MAX6657/MAX6658/MAX6659

control can be used to reduce the supply current in
portable-equipment applications. The conversion rate
byte’s POR state is 08h (16Hz). The MAX6657/
MAX6658/MAX6659 use only the 4 least-significant bits
(LSBs) of this register. The 4 most-significant bits
(MSBs) are “don’t care” and should be set to zero when
possible. The conversion rate tolerance is ±25% at any
rate setting.

Valid A/D conversion results for both channels are
available one total conversion time (125ms nominal,
156ms maximum) after initiating a conversion, whether
conversion is initiated through the

RUN/STOP bit, hard-

ware

STBY pin, one-shot command, or initial power-up.

Slave Addresses

The MAX6657/MAX6658 have a fixed address of 98h.
The MAX6659 can be programmed to have one of three
different addresses, allowing up to three devices to
reside on the same bus without address conflicts. Table
8 lists address information.

The address pin state is checked at POR only, and the
address data stays latched to reduce quiescent supply
current due to the bias current needed for high-Z state
detection.

The MAX6657/MAX6658/MAX6659 also respond to the
SMBus Alert Response slave address (see Alert
Response Address
section).

POR and UVLO

The MAX6657/MAX6658/MAX6659 have a volatile
memory. To prevent unreliable power-supply conditions

from corrupting the data in memory and causing erratic
behavior, a POR voltage detector monitors V

CC

and

clears the memory if V

CC

falls below 1.7V (typ, see

Electrical Characteristics). When power is first applied
and V

CC

rises above 2.0V (typ), the logic blocks begin

operating, although reads and writes at V

CC

levels

below 3.0V are not recommended. A second V

CC

com-

parator and the ADC undervoltage lockout (UVLO)
comparator prevent the ADC from converting until there
is sufficient headroom (V

CC

= +2.8V typ).

Power-Up Defaults

Power-up defaults include:

ADC begins autoconverting at a 16Hz rate (legacy
resolution).

THIGH and TLOW registers are set to default limits,
respectively.

Interrupt latch is cleared.

Address-select pin is sampled (MAX6659 only).

Command register is set to 00h to facilitate quick
internal Receive Byte queries.

Hysteresis is set to 10°C.

Transistor type is set to a substrate or common col-
lector PNP.

14

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DATA

CONVERSION RATE (Hz)

00h

0.0625

01h

0.125

02h

0.25

03h

0.5

04h

1

05h

2

06h

4

07h

8

08h

16

09h

16

0Ah-FFh

Reserved

ADD CONNECTION

ADDRESS

GND

98h

V

CC

9Ch

Floating

9Ah

Table 8. Slave Address Decoding for
MAX6659

Note: Extended resolution applies only for conversion rates of
4Hz or slower.

Table 7. Conversion-Rate
Control Byte

BIT

NAME

FUNCTION

7 (MSB)

ADD7

6

ADD6

5

ADD5

4

ADD4

3

ADD3

2

ADD2

1

ADD1

Provide the current
MAX6659 slave address
that was latched at POR
(Table 8)

0 (LSB)

1

Logic 1

Table 9. Read Format for Alert Response
Address (000 1100)

±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms