参数资料
型号: ADM1026JST-REEL7
厂商: ON Semiconductor
文件页数: 18/55页
文件大小: 0K
描述: IC CNTRL SYS REF/EEPROM 48LQFP
产品变化通告: MFG CHG Notification ADI to ON Semi
Product Obsolescence 30/Sept/2009
标准包装: 1
功能: 硬件监控器
传感器类型: 内部和外部
感应温度: 0°C ~ 100°C
精确度: ±3°C(最小值)
拓扑: ADC,比较器,多路复用器,寄存器库
输出类型: SMBus?
输出警报:
输出风扇:
电源电压: 3 V ~ 5.5 V
工作温度: 0°C ~ 100°C
安装类型: 表面贴装
封装/外壳: 48-LQFP
供应商设备封装: 48-LQFP(7x7)
包装: 标准包装
其它名称: ADM1026JSTREELDKR
ADM1026
I +
+ 78 nA
3.0 V 711 m s
100 k W
273 ms
This is a problem only if the ADC output must be full scale
when the negative voltage is zero.
Symmetrical bipolar input ranges can be accommodated
easily by making V OS equal to the full-scale voltage of the
analog input, and by adding a third resistor to set the positive
full scale.
For example, when V BAT = 3.0 V,
(eq. 9)
where T PULSE = V BAT measurement time (711 m s typical),
T PERIOD = time to measure all analog inputs (273 ms
typical), and V BAT input battery protection.
A IN(0–9)
V IN
+V OS
R2
R1
R3
V BAT Input Battery Protection
In addition to minimizing battery current drain, the V BAT
measurement circuitry was specifically designed with
battery protection in mind. Internal circuitry prevents the
battery from being back-biased by the ADM1026 supply or
through any other path under normal operating conditions.
In the unlikely event of a catastrophic ADM1026 failure, the
R1 +
V OS
Figure 29. Scaling and Offsetting A IN0 ? A IN9
for Bipolar Inputs
V f s *
R2 (eq. 5)
Note that R3 has no effect as the input voltage at the device
ADM1026 includes a second level of battery protection
including a series 3 k W resistor to limit current to the battery,
as recommended by UL. Thus, it is not necessary to add a
series resistor between the battery and the V BAT input; the
battery can be connected directly to the V BAT input to
improve voltage measurement accuracy.
R1 +
for A IN0 through A IN5
R1 +
for A IN6 through A IN9
pin is zero when V IN = negative full scale.
V f s * 3.0
R3 3.0
V f s * 2.5
R3 2.5
(eq. 6)
(eq. 7)
4.5pF
V BAT
49.5k ?
82.7k ?
3k ?
3k ?
DIGITAL
CONTROL
ADC
Also, note that R2 has no effect as the input voltage at the
device pin is equal to V OS when V IN = positive full scale.
Battery Measurement Input (V BAT )
The V BAT input allows the condition of a CMOS backup
battery to be monitored. This is typically a lithium coin cell
such as a CR2032. The V BAT input is accurate only for
voltages greater than 1.5 V (see Figure 14). Typically, the
battery in a system is required to keep some device powered
on when the system is in a powered-off state. The V BAT
measurement input is specially designed to minimize battery
drain. To reduce current drain from the battery, the lower
resistor of the V BAT attenuator is not connected, except
whenever a V BAT measurement is being made. The total
current drain on the V BAT pin is 80 nA typical (for a
maximum V BAT voltage = 4.0 V), so a CR2032 CMOS
battery functions in a system in excess of the expected 10
years. Note that when a V BAT measurement is not being
made, the current drain is reduced to 6 nA typical. Under
normal voltage measurement operating conditions, all
measurements are made in a round-robin format, and each
reading is actually the result of 16 digitally averaged
Figure 30. Equivalent V BAT Input Protection Circuit
Reference Output (V REF )
The ADM1026 offers an on-chip reference voltage
(Pin 24) that can be used to provide a 1.82 V or 2.5 V
reference voltage output. This output is buffered and
specified to sink or source a load current of 2 mA. The
reference voltage outputs 1.82 V if Bit 2 of Configuration
Register 3 (Address 07h) is 0; it outputs 2.5 V when this bit
is set to 1. This voltage reference output can be used to
provide a stable reference voltage to external circuitry such
as LDOs. The load regulation of the V REF output is typically
0.15% for a sink current of 2 mA and 0.15% for 2 mA source
current. There may be some ripple present on the V REF
output that requires filtering ( ? 4 m V MAX ). Figure 31 shows
the recommended circuitry for the V REF output for loads less
than 2 mA. For loads in excess of 2 mA, external circuitry,
such as that shown in Figure 32, can be used to buffer the
V REF output.
ADM1026
measurements. However, averaging is not carried out on the
V BAT measurement to reduce measurement time and
therefore reduce the current drain from the battery.
V REF
24
10k ?
0.1 ? F
V REF
The V BAT current drain when a measurement is being
made is calculated by:
I +
V BAT
100 k W
T PULSE
T PERIOD
(eq. 8)
Figure 31. V REF Interface Circuit for V REF Loads < 2 mA
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