ADM1023
Rev. 8 | Page 12 of 18 | www.onsemi.com
Configuration Register
Two bits of the configuration register are used. If Bit 6 is 0,
which is the power-on default, the device is in operating mode
with the ADC converting (see Table 9). If Bit 6 is set to 1, the
device is in standby mode and the ADC does not convert.
Standby mode can also be selected by taking the
STBY
pin low.
In standby mode, the values of remote and local temperature
remain at the value they were before the part was placed in
standby mode.
Bit 7 of the configuration register is used to mask the
ALERT
output. If Bit 7 is 0, which is the power-on default, the
ALERT
output is enabled. If Bit 7 is set to 1, the
ALERT
output is
disabled.
Table 9. Configuration Register Bit Assignments
Bit Name Function Power-On Default
7 MASK1 0 =
ALERT
Enabled 0
1 =
ALERT
Masked
6
RUN
/STOP 0 = Run 0
1 = Standby
5 to 0 Reserved 0
Conversion Rate Register
The lowest three bits of this register are used to program the
conversion rate by dividing the ADC clock by 1, 2, 4, 8, 16, 32,
64, or 128, to give conversion times from 125 ms (Code 0x07)
to 16 seconds (Code 0x00). This register can be written to and
read back over the SMBus. The higher five bits of this register
are unused and must be set to 0. Use of slower conversion times
greatly reduces the device’s power consumption, as shown in
Table 10.
Table 10. Conversion Rate Register Code
Data Conversion/Sec
Average Supply Current
μA Typ at V
CC
= 3.3 V
0x00 0.0625 150
0x01 0.125 150
0x02 0.25 150
0x03 0.5 150
0x04 1 150
0x05 2 150
0x06 4 160
0x07 8 180
0x08 to 0xFF Reserved
Limit Registers
The ADM1023 has six limit registers to store local and remote,
high and low temperature limits. These registers can be written
to and read back over the SMBus. The high limit registers
perform a > comparison, while the low limit registers perform
a < comparison. For example, if the high limit register is
programmed as a limit of 80°C, measuring 81°C results in an
alarm condition. Even though the temperature range is 0 to
127°C, it is possible to program the limit register with negative
values. This is for backward-compatibility with the ADM1021.
One-Shot Register
The one-shot register is used to initiate a single conversion and
comparison cycle when the ADM1023 is in standby mode, after
which the device returns to standby. This is not a data register
as such, and it is the write operation that causes the one-shot
conversion. The data written to this address is irrelevant and
is not stored.
SERIAL BUS INTERFACE
Control of the ADM1023 is carried out via the serial bus. The
ADM1023 is connected to this bus as a slave device, under the
control of a master device. Note that the SMBus SDA and SCLK
pins are three-stated when the ADM1023 is powered down, and
they do not pull down the SMBus.
ADDRESS PINS
In general, every SMBus device has a 7-bit device address
(except for some devices that have extended, 10-bit addresses).
When the master device sends a device address over the bus,
the slave device with that address responds. The ADM1023
has two address pins, ADD0 and ADD1, to allow selection of
the device address, so that several ADM1023s can be used on
the same bus and to avoid conflict with other devices. Although
only two address pins are provided, these pins are three-state
and can be grounded, left unconnected, or tied to V
DD
, so that a
total of nine different addresses are possible, as shown in Table 11.
Note that the state of the address pins is sampled only at power-
up, so changing them after power-up has no effect.
Table 11. Device Addresses
1
ADD0 ADD1 Device Address
0 0 0011 000
0 NC 0011 001
0 1 0011 010
NC 0 0101 001
NC NC 0101 010
NC 1 0101 011
1 0 1001 100
1 NC 1001 101
1 1 1001 110
1
ADD0 and ADD1 are sampled at power-up only.
The serial bus protocol operates as follows: