EVAL-ADM1023EB Datasheet ADM1023ARQZ, EVAL-ADM1023EB, ADM1023ARQ | P10-P12

ADM1023

Rev. 8 | Page 10 of 18 | www.onsemi.com

Δβ

7300

(mA)

MAX

< 4.5

= I

β+1

00058-015

Figure 15. Variation of β with Collector Currents

Expressing the collector current in terms of the emitter current

= I

[β/(β + 1)]

where:

β(300 μA) = β(7 μA)(1 + ε ).

ε = Δβ/β and β = β(7 μA).

Rewriting the equation for ΔV

, to include the ideality factor,

n, and beta, β yields

()( )

()

⎥

⎦

⎤

⎢

⎣

⎡

+×+

×=Δ Nn

nKT

βε

(3)

All β variations of less than 1% (ε < 0.01) contribute to

temperature errors of less than 0.4°C.

TEMPERATURE DATA FORMAT

One LSB of the ADC corresponds to 0.125°C, so the ADM1023

can measure from 0°C to 127.875°C. The temperature data

format and extended temperature resolution are shown in

Table 4 and Table 5.

Table 4. Temperature Data Format

(Local Temperature and Remote Temperature High Byte)

Temperature (°C)

Digital Output

0 0 000 0000

1 0 000 0001

10 0 000 1010

25 0 001 1001

50 0 011 0010

75 0 100 1011

100 0 110 0100

125 0 111 1101

127 0 111 1111

The ADM1023 differs from the ADM1021 in that the temperature resolution

of the remote channel is improved from 1°C to 0.125°C, but it cannot

measure temperatures below 0°C. If negative temperature measurement is

required, the ADM1021 should be used.

The results of the local and remote temperature measurements

are stored in the local and remote temperature value registers

and are compared with limits programmed into the local and

remote high and low limit registers.

Table 5. Extended Temperature Resolution

(Remote Temperature Low Byte)

Extended Resolution (°C) Remote Temperature Low Byte

0.000 0000 0000

0.125 0010 0000

0.250 0100 0000

0.375 0110 0000

0.500 1000 0000

0.625 1010 0000

0.750 1100 0000

0.875 1110 0000

The ADM1023 contains registers that are used to store the

results of remote and local temperature measurements and high

and low temperature limits, and to configure and control the

device. A description of these registers follows, and further

details are given in Table 6 to Table 10. Most of the registers

for the ADM1023 are dual-port and have different addresses

for read and write operations. Attempting to write to a read

address or to read from a write address produces an invalid

result. Register addresses above 0x14 are reserved for future

use or factory test purposes and should not be written to.

Address Pointer Register

The address pointer register does not have, nor does it require,

an address, because it is the register to which the first data byte

of every write operation is automatically written. This data byte

is an address pointer that sets up one of the other registers for

the second byte of the write operation or for a subsequent read

operation.

Value Registers

The ADM1023 has three registers to store the results of local

and remote temperature measurements. These registers are

written to by the ADC and can only be read over the SMBus.

The Offset Register

Two offset registers are provided at Address 0x11 and

Address 0x12. These are provided so that the user may remove

errors from the measured values of remote temperature. These

errors may be introduced by clock noise and PCB track resis-

tance. See Table 7 for an example of offset values.

The offset value is stored as an 11-bit, twos complement value

in Register 0x11 (high byte) and Register 0x12 (low byte, left

justified). The value of the offset is negative if the MSB of

is 0. This value is added to the remote temperature. These

registers default to 0 at power-up and have no effect if nothing

is written to them. The offset register can accept values from

−128.875°C to +127.875°C. The ADM1023 detects overflow so

the remote temperature value register does not wrap around

+127°C or −128°C.

ADM1023

Rev. 8 | Page 11 of 18 | www.onsemi.com

Table 6. List of ADM1023 Registers

Read Address (Hex) Write Address (Hex) Name Power-On Default

Not applicable Not applicable Address pointer Undefined

00 Not applicable Local temperature value 1000 0000 (0x80) (−128°C)

01 Not applicable Remote temperature value high byte 1000 0000 (0x80) (−128°C)

02 Not applicable Status Undefined

03 09 Configuration 0000 0000 (0x00)

04 0A Conversion rate 0000 0010 (0x02)

05 0B Local temperature high limit 0111 1111 (0x7F) (+127°C)

06 0C Local temperature low limit 1100 1001 (0xC9) (−55°C)

07 0D Remote temperature high limit high byte 0111 1111 (0x7F) (+127°C)

08 0E Remote temperature low limit high byte 1100 1001 (0xC9) (−55°C)

Not applicable 0F

One-shot

10 Not applicable Remote temperature value low byte 0000 0000

11 11 Remote temperature offset high byte 0000 0000

12 12 Remote temperature offset low byte 0000 0000

13 13 Remote temperature high limit low byte 0000 0000

14 14 Remote temperature low limit low byte 0000 0000

19 Not applicable Reserved 0000 0000

20 21 Reserved Undefined

FE Not applicable Manufacturer device ID 0100 0001 (0x41)

FF Not applicable Die revision code 0011 xxxx (0x3x)

Writing to Address 0F causes the ADM1023 to perform a single measurement. It is not a data register as such; thus, it does not matter what data is written to it.

Table 7. Offset Values

Remote Remote

Temperature Temperature

Offset Registers Offset (With (Without

0x11 0x12 Value Offset) Offset)

1111 1100 0000 0000 −4°C 14°C 18°C

1111 1111 0000 0000 −1°C 17°C 18°C

1111 1111 1110 0000 −0.125°C 17.875°C 18°C

0000 0000 0000 0000 0°C 18°C 18°C

0000 0000 0010 0000 +0.125°C 18.125°C 18°C

0000 0001 0000 0000 +1°C 19°C 18°C

0000 0100 0000 0000 +4°C 22°C 18°C

Status Register

Bit 7 of the status register (see Table 8) indicates that the ADC is

busy converting when it is high. Bit 6 to Bit 3 are flags indicating

the results of the limit comparisons.

If the local and/or remote temperature measurement is above

the corresponding high temperature limit or below the corre-

sponding low temperature limit, one or more of these flags will

be set. Bit 2 is a flag that is set if the remote temperature sensor

is open-circuit. These five flags are NOR’d together, so that if

any of them are high, the

ALERT

interrupt latch is set, and the

ALERT

output goes low.

Reading the status register clears the five flag bits, provided the

error conditions that caused the flags to be set have gone away.

While a limit comparator is tripped due to a value register

containing an out-of-limit measurement or the sensor is open-

circuit, the corresponding flag bit cannot be reset. A flag bit can

be reset only if the corresponding value register contains an in-

limit measurement, or the sensor is good.

The

ALERT

interrupt latch is not reset by reading the status

ALERT

output has been serviced

by the master reading the device address, provided the error

condition has gone away and the status register flag bits have

been reset.

Table 8. Status Register Bit Assignments

Bit Name Function

7 BUSY At 1 when ADC converting

6 LHIGH

At 1 when local high temp limit tripped

5 LLOW

At 1 when local low temp limit tripped

4 RHIGH

At 1 when remote high temp limit tripped

3 RLOW

At 1 when remote low temp limit tripped

2 OPEN

At 1 when remote sensor open-circuit

1 to 0 Reserved

These flags stay high until the status register is read or they are reset by POR.

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

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

= 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

, 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

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

ADD0 and ADD1 are sampled at power-up only.

The serial bus protocol operates as follows:

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18

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