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ADP1046AW Datasheet(PDF) 28 Page - Analog Devices
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ADP1046AW Datasheet(HTML) 28 Page - Analog Devices
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Rev. 0 | Page 28 of 88
The output power value register (Register 0x19) is the product
of the VS3 voltage value and the CS2 current value. Therefore,
a combination of the formulas in the Voltage Readings section
and the CS2+, CS2− Pins section is used to calculate the power
reading in watts. This register is a 16-bit word. It multiplies two
12-bit numbers and discards the eight LSBs.
= 12 V × 4.453 A = 53.436 W
POWER MONITORING ACCURACY
The ADP1046AW power monitoring accuracy is specified
relative to the full-scale range of the signal that it is measuring.
FIRST FLAG FAULT ID AND VALUE REGISTERS
When the ADP1046AW registers several fault conditions, it
stores the value of the first fault in a dedicated register. For example,
if the overtemperature (OTP) fault is registered followed by an
OVP fault, the OTP flag is stored in the first flag ID register
(Register 0x10). This register gives the user more information
for fault diagnosis than a simple flag. The contents of this register
are latched, meaning that they are stored until read by the user.
The contents are also reset by toggling PSON. If a flag is set to
be ignored, it does not appear in the first flag register.
EXTERNAL FLAG INPUT (FLAGIN PIN)
The FLAGIN pin can be used to send an external fault signal into
the ADP1046AW. Register 0x0A[3:0] can be used to program the
FLAGIN flag to trigger an action.
TEMPERATURE READINGS (RTD PIN)
The RTD pin is set up for use with an external negative tempera-
ture coefficient (NTC) thermistor (see Figure 38). The RTD pin
has an internal programmable current source. An ADC monitors
the voltage on the RTD pin.
The RTD temperature value register, Register 0x1A, is updated
every 10 ms. The ADP1046AW stores every ADC sample for 10 ms
and then outputs the average value at the end of the 10 ms period.
The RTD ADC has an input range of 1.6 V and a resolution of
12 bits, which means that the LSB size is 1.6 V/4096 = 390.625 µV.
The user is limited to an input range of 1.3 V, which means that the
maximum ADC output code is limited to 1.3 V/390.6 µV = 3328.
The output of the RTD ADC is linearly proportional to the volt-
age on the RTD pin. However, thermistors exhibit a nonlinear
function of resistance vs. temperature. Therefore, the user must
perform postprocessing on the RTD ADC reading to accurately
read the temperature.
By connecting an external resistor (R
) in parallel with the NTC
thermistor (TH), a constant current can be used to achieve linear-
ization (see Figure 37).
Figure 37. Temperature Measurement Using Thermistor
An internal, precision current source of 10 µA, 20 µA, 30 µA,
or 40 µA can be selected in Register 0x11. This current source
can be trimmed by means of an internal DAC to compensate
for thermistor accuracy (see the RTD/OTP Trim section). The
user can select the size of the output current source using
Bits[7:6] of Register 0x11.
The ADP1046AW implements a linearization scheme based on
a preselected combination of external components and current
selection for best performance when measuring linearized tem-
peratures in degrees Celsius in the industrial range.
For more information about the required thermistor and selecting
and trimming the precision current sources, see the Temperature
Linearization Scheme section.
Optionally, the user can process the RTD reading and perform
postprocessing in the form of a lookup table or polynomial
equation to match the specific NTC thermistor used. With the
internal current source set to 46 µA, the equation to calculate
the ADC code at a specified NTC thermistor value (Rx) is given
by the following formula:
ADC CODE = 46 µA × Rx/1.6 × 4096
For example, at 60°C, the NTC thermistor at the RTD pin is
RTD_ADC_CODE = 46 µA × 21.82 kΩ/1.6 × 4096 = 2570
VALUE IN °C
Figure 38. RTD Pin Internal Details
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