Features

ADM1021 alternative

Film and remote sensing temperature

No need to calibrate

*[123 ] Sensor on the film 1 ° C accuracy

* 3 ° C remote sensor accuracy

* Able over temperature/low temperature limit [

123]

* The programmable conversion rate

* 2 line SMBUS serial interface

* Support system management bus ( SMBUS) Alert

* The maximum working current 200 mia

* 1 millhot current remote current

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3 V to 5.5 V power supply

*

16 guide small QSOP package Application

*

desktop computer [ 123]

*

Note computer Smart battery

* Industry Controller

* Telecom equipment

* Instrument

Product description

ADM1021A is a double Channel digital thermometer and low temperature/ultra -temperature alarm, for personal computers and other systems that require heat monitoring and management. This device can use the PNP transistor connected to the PNP transistor to measure the temperature of the microprocessor. The transistor can be provided on the chip in the case of the Pentium III or a similar processor. Essence A new measurement technology eliminates the absolute value of the transmitting polar voltage of the transistor base, so no calibration is required. The second measurement channel measurement of the output of the temperature sensor on the tablet to monitor the temperature of the equipment and its environment. ADM1021A communicates through dual -line interfaces compatible with SMBUS standards. Low -temperature super temperature restrictions can be programmed in the device through serial bus. When the chip or remote temperature exceeds the range, alarm output signal will be issued. This output can be used as interrupt or SMBUS alert.

ADM1021A - Typical performance features

Function description

adm1021a Including a special lossThe dual-channel A-D converter of the signal adjustment function can be operated by remote and the diode temperature sensor on the film. When ADM1021A works normally, the A-D converter works in free operation. The simulation input multi -road reused device alternates the temperature sensor on the film to measure its local temperature, or choose a remote temperature sensor. These signals are digitized by ADC, and the results are stored in local and remote temperature value registers as 8 -bit and two supplements. The measurement results were compared with the local and long -range, high and low temperature limit stored in the four films. The comparison that exceeds restrictions to generate a sign stored in a state register, and one or more results that exceed the restrictions will cause the alarm output to be pulled down.

You can program the limit register through the serial system management bus and control and configure the device.

The content of any register can also be read back by SMBUS.

Control and configuration function includes:

Switch the device between normal operation and standby mode.

shield or enable the alarm output.

Select conversion rate.

When the initial power is powered, the remote and local temperature value defaults to -128 ° C. Since the device is usually transformed by power, the local and long -range temperatures are measured, and these values are stored before comparing the storage limit. However, if the part is powered on in the standby mode (the STBY pin is low), the new value will not be written to the register before comparing the comparison. As a result, both RLOW and LLOW were triggered in the state register, resulting in a warning output. It can be cleared through one of the following two methods:

1. The local and remote lower limit is changed to -128 ° C and read the status register (and then remove the alarm output).

2. Take the part from the standby status and read the status register (and then remove the alarm output). Only when the measurement value is within the limit range, this works.

Measurement method

A simple way to measure the temperature is to use the negative temperature coefficient of the diode, or the base of the transistor of the transistor to work under constant current. Unfortunately, this technology requires calibration to eliminate the effect of VBE's absolute value. The absolute value of VBE varies from equipment.

The technology used in ADM1021A is to measure the change of VBE when operating devices in two different currents.

This is given by the following personnel:

Among them: K is Bolzman's constant,

q is electronics from electronics. Charge (1.6 × 10-19 Kulun),

T is an absolute temperature, the unit is Kelvins, [12]3] N is the ratio of two currents.

FIG. 2 shows the input signal adjustment for measuring the output of the external temperature sensor. This figure shows an external sensor as a substrate transistor and is used to monitor temperature on some microprocessors, but it can also be a separate transistor. If a separate transistor is used, the collector will not be ground and should be connected to the base. In order to prevent ground noise interference measurement, the sensors are more negative and do not refer to grounding, but instead bias on the ground through the internal diode of the D-input. If the sensor works in the noise environment, you can choose to add C1 as the noise filter. Its value is usually 2200 PF, but it should not exceed 3000 PF. For more information about C1, see the precautions for layout.

In order to measure ∏VBE, the sensor switches between the working current of i and N × i. The generated waveform removes noise through a 65 kHz low -pass filter, and then enters the cut wave stable amplifier. The amplifier performs the enlarged and correction function of the waveform to generate a proportional DC voltage to the ∏VBE. This voltage is measured by ADC to provide the temperature output in the 8 -bit dual -second replacement format. In order to further reduce the impact of noise, digital filtering is performed by the results of the average 16 measurement cycle.

The signal regulation and measurement of the internal temperature sensor performed in a similar way.

Differences between ADM1021 and ADM1021A

Although ADM1021A is aimed at ADM1021, these two devices are different.

The following is a summary of these differences and changes.

1. ADM1021A forced to sensor the current through the remote sensing temperature temperature to the diode, usually 205 Weire, instead of 90 micro -security for ADM1021. This is mainly to improve the noise resistance of parts.

2. Due to the larger remote sensor source current, the working current of ADM1021A is higher than the ADM1021, usually 205 mAh instead of 160 mAh.

3. The temperature measurement range of ADM1021A is 0 ° C to 127 ° C, while the temperature measurement range of ADM1021 is -128 ° C to+127 ° C. Therefore, if you need to measure negative temperature, you should use ADM1021.

4. The power-over and heavy-duty heavy standing value of remote and local temperature values is -128 ° C in ADM1021A, and 0 ° C in ADM1021. When the component is transformed by power power, unless the part is in the standby mode, that is, the pin 15 is pulled down), the part will measure the actual value of remote and local temperature and write it to the register.

5. Four MSBs of the revised register can be used for identifying components. ADM1021 revised the register to read 0xh, and ADM1021A reads 3XH.

6. The default value of the address pointer register is ADM1021It is not defined in A, which is equal to 00h in ADM1021. Therefore, before reading in ADM1021A, the value must be written to the address pointer register. ADM1021 can read the local temperature without writing the address pointer register because it defaults to the local temperature measurement register when it is powered on.

7. Set up mask positions on ADM1021A (bit 7 configuration register) will block the current and future alarms. On the ADM1021, the shielded position only shields the future alarm. Ara must be used to remove any current alert.

Temperature data format

A LSB of ADC corresponds to 1 ° C, so ADC can theoretically measure the temperature from -128 ° C to+127 ° C. The temperature of 0 ° C, so the actual range is 0 ° C temperature data format as shown in Table I. C to 127C.

Local and remote temperature measurement results are stored in local and long -range temperature registers, and are compared with local and long -range high and low -limit registers.

The register

ADM1021A contains nine registers for storing remote and local temperature measurement results, high temperature and low temperature limit, and configuration and control equipment. The following is the description of these registers, which gives further details from Table II to IV. It should be noted that the register of the ADM1021A is dual -port with different read and write addresses. Trying to write the reading address or read from the writing address will cause an invalid result. The register address above 0fh is retained for future use or for factory testing, and should not be written.

Address pointer register

The address pointer register has no address, and does not require the address, because it is the first data byte that is automatically written in each written data. This data byte is a address pointer that sets one of the other registers for the second byte or follow -up operation of the operation.

Value register

ADM1021A has two registers to store the results of local and remote temperature measurement. These registers are written by ADC and can only be read through SMBUS.

Status register

The bit 7 of the state register indicates that ADC is usually busy in high -electricity. Bit 5 to 3 is a sign of the result comparison result.

If the measured value of the local and/or remote temperature is higher than the corresponding high temperature limit or below the corresponding low temperature limit, one or more of these logos will be set. Bit 2 is a sign set when the remote temperature sensor is opened. These five signs are not together, so if any of them is high, the alarm interrupt locks will be set, and the alarm output will become lower. If the error conditions of the setting logo disappear, the read status register will remove the five signs. When comparisonThe corresponding logo can not be reset due to the value of the value register containing the over -limit measurement, or when the sensor opens the road. Only when the corresponding value register contains the intra -limited measurement value or the sensor is good, the logo can be reset.

Alarm interrupt lock memory is not reset by reading status registers, but when the host of the device address is provided to provide services to the alarm output service, the host is heavy when the alarm output is provided. The premise is that the error conditions have disappeared, and the status register logo has been reset.

Configure the register

Use two digits of the configuration register. If the bit 6 is 0 (the default is the boot), the device is in the working mode of the ADC conversion. If the bit 6 is set to 1, the device is in the standby mode and the ADC will not be converted. The standby mode can also be selected by setting the spare pin as a low level. In the standby mode, the value stored in remote and local temperature registers is kept in the standby state. The seventh bit of the configuration register is used to block the output of the shielding alert. If the bit 7 is 0 (the default is the boot), the alarm output is enabled. If the bit 7 is set to 1, the alarm output is banned.

Conversion rate register

The minimum three -bit of the register is used to divide the ADC clock with 1, 2, 4, 8, 16, 32, 32, 32. 64 or 128 to program the conversion rate to give the conversion time from 125 ms (code 07h) to 16 s (code 00h). This register can be written to SMBUS and read through SMBUS. The high level of this register is unused and must be set to zero. The slow conversion time greatly reduces the power consumption of the equipment, as shown in Table V.

Extreme register

ADM1021A has four extreme registers for storing local and long -range, high temperature and low temperature limit. These registers can be written to SMBUS and read through SMBUS. The upper limit register executes gt; compares, and the lower limit register executes lt; compares. For example, if the upper limit register programming is 80 ° C limit, the measurement of 81 ° C will cause alarm conditions. Even if the temperature measurement range is between 0 and 127 ° C, negative programming restrictions can be used. This is to be compatible with ADM1021.

One -time register

When the ADM1021A is in the standby mode, the register is used to start a conversion and comparative cycle, and then the device returns the standby state. This is not the data register itself, but the writing operation of a single conversion. The data written to this address is not related and will not be stored.

Serial bus interface

The control of ADM1021A is executed by serial bus. Under the control of the main device, the ADM1021A is connected from the device to this bus. PleaseIt means that when the ADM1021A is powered off, the SMBUS and SCL tube feet are three states, which will not lower SMBUS.

Address Tube

Generally speaking, each SMBUS device has a 7 -bit device address (except for some devices that extend 10 -bit addresses). When the main device sends the device address through the bus, the device with the address will respond. The ADM1021A has two addresses ADD0 and ADD1, which is used to select the device address in order to use multiple ADM1021A on the same bus, and/or avoid conflicting with other devices. Although there are only two address tube feet, these are three states that can be grounded, kept or bound to VDD, so there can be a total of nine different addresses, as shown in Table 6.

It should be noted that the state of the address tube foot is only sampled during power, so changing the address tube foot after power -on will not have any effect.

The operation of the serial bus protocol is as follows:

1. The conversion of high to low, while the serial clock line SCLK remains high. This means that the address/data stream will follow. All from the engine response starting conditions connected to the serial bus and shifted in the next 8 digits, including 7 -bit addresses (first MSB) plus R/W bit, R/W bit determine the direction of data transmission direction of data transmission direction That is, the data will be written or read from the machine equipment.

The address corresponds to the peripheral device where the sending address is sent by the low cycle before the ninth hour pulse (referred to as the confirmation position) to lower the data cable to respond. All other devices on the bus are now idle, while the selected devices are waiting to read or write data from it. If the R/W bit is 0, the main device will be written into the device. If the R/W bit is 1, the main device will read from the device.

2. The data is sent through the order of 9 clock pulses through the serial bus. The transition on the data cable must occur within the low cycle of the clock signal and keep it stable during the high cycle, because the low -to -high transition of the clock can be interpreted as a stop signal when the clock is high. The number of data byte by series transmitted through the serial bus can be limited by the number of data by serialary bus that can be processed by the main device and the content that can be processed from the device.

3. When reading or writing all data bytes, stop conditions will be established. In the writing mode, the host will pull the data cable to raise the data cable during the 10th clock pulse to stop the conditions. In the reading mode, the main device will cover the confirmation bit by raising the data cable within the low cycle before the ninth hour pulse. This is the so -called non -recognition. Then, the host will take the low data cable within the low cycle before the 10th clock pulse, and then take the high data cable during the 10th clock pulse period to assert the stop condition.

In one operationAmong them, any amount of data of any amount of data can be transmitted through the serial bus, but it is impossible to mix and write in a operation, because the type of operation is determined at the beginning, and it cannot be changed later without starting a new operation.

For ADM1021A, the writing operation contains one or two bytes, and the reading operation contains one byte.

To write the data into one of the device data registers or read the data from it, the address pointer register must be set to address the correct data register, and then the data can be written or readable. The first byte of the writing operation always contains valid addresses stored in the address pointer register. If the data is written to the device, the writing operation includes the second data byte of the register selected by the written address pointer register.

As shown in Figure 3. The device address is sent through the bus, and then the R/W is set to 0. Follow two data bytes. The first data byte is the address of the internal data register to be written, which is stored in the address pointer register. The second data byte is to write data to the internal data register.

When reading the data from the register, there are two possibilities:

1. If the address pointer value of the ADM1021A address pointer value is unknown or not the required value, it must be set to correct Value, then read the data from the required data registers. This is done by performing writing operations on ADM1021A as before, but only data bytes containing the register read address are sent because the data will not be written to the register. As shown in Figure 4.

Then perform the reading operation, including the serial bus address, the R/W bit set to 1, and then read the data byte from the data register. As shown in Figure 5.

2. If the known address pointer register is already located at the required address, you can read the data from the corresponding data register without the need to write the address pointer register first, so you can omit Figure 4.

Notes

1. Although you can read the data by the data register without writing the address pointer register first, but if the address pointer register is already in the correct value, it will not not be the right value, then it will not The data may be written into the register without writing the address pointer register, because the first data bytes written in the address are always written to the address pointer register.

2. Remember, the ADM1021A register has different read and write addresses. If you want to write the data to the register, the write address of the register must be written into the address pointer, but the data cannot be read from the address. The reading address of the register must be written into the address pointer before reading the data from the register.

Alarm output

Whenever the measurement value beyond the limit or if the remote temperature sensor opens the road, the alarm output will turn lower. This is an open drainage pipe, which requires 10 kΩ pull to VDD. Several alarm output can be connected together, so if one or more alarm output becomes lower, the public line will become lower.

Alarm output can be used as a interrupt signal of a processor or SMBalert. The subordinate device on SMBUS usually cannot send signals they want to talk to in the main device, but the Smbalert function allows them to do so.

One or more alarm output is connected to Smbalert to connect to the host line. When one of the devices lower the Smbalert line, the following process will occur, as shown in Figure 6.

1. Smbalert was pulled down.

2. The host starts the read operation and sends the alarm response address (ARA 0001 100). This is a conventional call address that cannot be used as a specific device address.

3. Equipment with a low alarm response response address with low alarm output, and the host read its device address. The address of the device is now known and can be queried in a normal way.

4. If the alarm output of multiple equipment is low, according to the normal SMBUS arbitration, equipment with the lowest equipment address will have priority.

5. Once the ADM1021A responds to the alarm response address, it will reset its alarm output, provided that the error conditions of the alarm no longer exist. If the Smbalert line is kept low, the host will send ARA again, and push it according to this until all devices output of the alarm to the low level respond.

Low -power standby mode

ADM1021A can use hardware or software to enter the low -power standby mode, that is, by setting the STBY input to low, or setting the position of the register 6. When STBY is high or 6 low, ADM1021A works normally. When STBY is pulled down or the bit 6 is pulled up, ADC is suppressed, so any of the transitions that are undergoing will be terminated without writing the results into the corresponding value register.

SMBUS is still enabled. If there is no SMBUS activity, the power consumption in the standby mode will be reduced to less than 10 micro -security; if there are clocks and data signals on the bus, the power consumption will be reduced to 100 micro -security.

These two modes are similar but incomplete. When STBY is low, the conversion is completely banned. When setting 6 but STBY is high, you can start a single point conversion of the two channels by writing XXH to a single point register (address 0FH).

Sensor fault detection

ADM1021A has a fault detector at the D+input terminal to detect whether the external sensor diode is disconnected. This is a simple voltage comparator. If the D+voltage exceeds VCC -1V (typical value), it will jump. Check the output of the comparator when starting the conversionIf the failure is detected, the position of the state register 2 is set.

If the remote sensor voltage is lower than the normal measurement range, for example, due to the short circuit of the diode, the ADC will output -128 ° C (1000 0000). Because the normal operating temperature range of the device is extended to 0 ° C, the output code can never be seen in normal operations, so it can be interpreted as a failure state.

In this regard, ADM1021A is different from and improved competitive devices. If the external sensor is short circuit, the output is zero. These devices may misunderstand the real 0 ° C measurement value as a fault state.

If the external diode channel is not used and short circuit, it can be cleared to remove the generated alarm by writing 80H (–128 ° C).

Application information

Factors affecting the precision of the remote sensing diode

ADM1021A design for the foundation of the substrate or discrete transistor in the processor. The substrate transistor is usually PNP type, and the collector is connected to the substrate. The discrete type can be PNP or NPN, which is connected as diode (the base -pair -pairing electrode short circuit). If the NPN transistor is used, the collector and the base are connected to D+, and the emission pole is connected to D-. If the PNP transistor is used, the set electrode and base pole are connected to D-and the emission pole is connected to D+.

对于衬底晶体管，用户没有选择，但是如果使用分立晶体管，则通过根据以下标准选择器件将获得最佳精度：

1、在最高工作温度下，6微The basal emission pole voltage of An Shi is greater than 0.25 V.

2. At the minimum operating temperature, the basal emission pole voltage of the basis is less than 0.95 volt at 100 micro -safety.

3. The base resistance is less than 100Ω.

4. The small changes of HFE (such as 50 to 150) show strict control of VBE characteristics.

The equivalent crystal tube in packaging of 2N3904, 2N3906 or SOT-23 is suitable for device suitable for use.

Thermal inertia and self -heating

The precision depends on the temperature of the remote sensing diode and/or internal temperature sensor of the internal temperature sensor. Many factors will affect this. Ideally, the sensor should maintain good thermal contact with the component of the system (such as a processor). Otherwise, the thermal inertia caused by the quality of the sensor will cause the sensor's response to temperature changes. In the case of remote sensor, this should not be a problem because it will be a substrate crystal tube in the processor or small packaging device, such as SOT-23 near it.

However, the sensor on the film is usually away from the processor, only monitor the general environmental temperature around the package. QSOP-16 packaged hot time constant is about 10 seconds.

In fact, the package will beThe brush circuit board performs electrical connections to achieve heat connection, so the temperature rise caused by self -heating can be ignored.

Precautions for layout

The digital circuit board may be an electrical noise environment, and because ADM1021A measures very small voltage from the remote sensor Essence The following preventive measures should be taken:

1. The ADM1021A is as close to the remote sensing diode as close as possible. If the worst noise source is avoided, such as clock generators, data/address bus, and CRT, this distance can be 4 to 8 inches.

2. Putting D+and D-track together, there are ground protection tracks on each side. If possible, a ground plane is provided below the track.

3. Use a wide track to minimize the inductance and reduce the pickup of noise. The minimum width and spacing of the track are recommended to be 10 mil.

4. Try to minimize the number of copper/solder joints that may cause thermocouple effect. At the place where copper/welded, make sure they are in D+and D-paths at the same temperature.

The thermocouple effect should not be a major problem, because 1 ° C corresponds to about 240 micro volt, and the thermocouple voltage is about 3 micro volt/degree Celsius. Unless there are two thermocouples with large temperature differences, the thermocouple voltage should be less than 240 slightly.

5. Place 0.1 μF bypass electric containers at a nearly VDD pin and place 2200 PF input filter capacitors near ADM1021A.

6. If the distance from the remote sensor is more than 8 inches, it is recommended to use twisted wires. This will work to about 6 to 12 feet.

7. For a very long distance (up to 100 feet), please use the shielded twisted wire, such as the Belden 8451 microphone cable. Connect the twisted wire to D+and D-, and the shield is shielded to GND near ADM1021A. Keep the shielded remote end unconnected to avoid grounding circuits.

Due to the use of switching current sources in the measurement technology, excessive cables and/or filter capacitors will affect measurement. When using a long cable, you can reduce or remove the filter capacitor.

Cable resistance will also introduce errors. The 1Ω series resistance introduces an error of about 1 ° C.

Application circuit

FIG. 8 shows the typical application circuit of ADM1021A, using a discrete sensor transistor tube connected by the twisted twisted wire. They only need them when the pull -pull function on SCLK, SDATA and Alert has not been provided in other locations in the system.

SCLK and SDATA pins of ADM1021A can be directly connected to SMBUS of the I/O chip. Figure 9 shows how to use this type of I/O controller integrates ADM1021A into the system.

The size of the shape

16 The thermal conductivity is reduced [qsop] (RQ-16)

The size unit is inch