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ADP1046AW Datasheet(PDF) 33 Page - Analog Devices
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ADP1046AW Datasheet(HTML) 33 Page - Analog Devices
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Rev. 0 | Page 33 of 88
POWER SUPPLY CALIBRATION AND TRIM
The ADP1046AW allows the entire power supply to be calibrated
and trimmed digitally in the production environment. It can
calibrate items such as output voltage and trim for tolerance
errors introduced by sense resistors and resistor dividers, as well
as its own internal circuitry. The part is factory trimmed, but it
can be retrimmed by the user to compensate for the errors intro-
duced by external components. The ADP1046AW GUI allows
the user to automatically revert the trim settings to their factory
To unlock the trim registers for write access, write to the
TRIM_PASSWORD register (Register 0x89). Write the
trim password twice (the factory default password is 0xFF).
The ADP1046AW allows the user enough trim capability to trim
for external components with a tolerance of 0.5% or better. If the
ADP1046AW is not trimmed in the production environment, it
is recommended that components with a tolerance of 0.1% or
better be used for the inputs to CS1, CS2, VS1, VS2, and VS3 to
meet data sheet specifications.
Using a DC Signal
A known voltage (Vx) is applied at the CS1 pin. The CS1 ADC
should output a digital code equal to Vx/1.4 × 4096. The CS1
gain trim register (Register 0x21) is adjusted until the CS1 ADC
value in Register 0x13[15:4] reads the correct digital code.
Using an AC Signal
A known current (Ix) is applied to the PSU input. This current
passes through a current transformer, a diode rectifier, and an
external resistor (R
) to convert the current information to a
voltage (Vx). This voltage is fed into the CS1 pin. The voltage
(Vx) is calculated as follows:
Vx = Ix × (N1/N2) × R
where N1/N2 is the turns ratio of the current transformer.
The CS1 ADC outputs a digital code equal to Vx/1.4 × 4096. The
CS1 gain trim register (Register 0x21) is adjusted until the CS1
ADC value in Register 0x13[15:4] reads the correct digital code.
The CS2 trim must compensate for offset and gain errors. The
offset error requires both an analog trim and a digital trim. This
error includes the mismatch of the level shifting resistors to the
inputs of the CS2± differential amplifier and the tolerance of the
current sense element.
CS2 Offset Trim
Offset errors can be introduced by the external level shifting
resistors and the internal current sources. It is best to use two
0.1% matched resistors or matched resistors within the same
It is important to perform the CS2 offset trim as described
in the following steps:
1. Set high-side or low-side current sensing using
2. Set the nominal full-scale sense resistor voltage drop in
Register 0x27 to 1 for the 120 mV range or to 0 for the
60 mV range.
3. Apply no-load current across the sense resistor.
4. Set the CS2 gain trim value to 0 (Register 0x23 = 0).
5. Set the CS2 digital offset trim value to 0 (Register 0x25 = 0).
6. Adjust the CS2 analog offset trim value in Register 0x24[6:0].
For the 120 mV range, adjust Register 0x24 until the CS2
value in Register 0x18[15:4] reads as close to 100 decimal
(0x64) as possible; this value must be greater than 50 (0x32).
For the 60 mV range, adjust Register 0x24 until the CS2
value in Register 0x18[15:4] reads as close to 200 decimal
(0xC8) as possible; this value must be greater than 100 (0x64).
7. Adjust the CS2 digital offset trim value in Register 0x25
until the CS2 value in Register 0x18[15:4] reads 0.
The offset trim is now completed, and the ADC code reads 0
when there is a no-load current across the sense resistor.
CS2 Gain Trim
After performing the offset trim, perform the gain trim to remove
any mismatch that is introduced by the sense resistor tolerance.
The ADP1046AW can trim for sense resistors with a tolerance
of 1% or better.
1. Apply a known load current (I
) across the sense resistor.
2. Adjust the CS2 gain trim value in Register 0x23[5:0] until
the CS2 value in Register 0x18[15:4] reads the value
calculated by the following formula:
CS2 Value = I
/FS × 4096
FS is the full-scale voltage drop (120 mV or 60 mV).
is the sense resistor value.
If CS2 is programmed to the 120 mV range and I
= 10 A,
= 10 mΩ, and FS = 120 mV,
CS2 Value = (10 A × 10 mΩ)/120 mV × 4096
CS2 Value = 3413 decimal
If CS2 is programmed to the 60 mV range and I
= 5 A,
= 5 mΩ, and FS = 60 mV,
CS2 Value = (5 A × 5 mΩ)/60 mV × 4096
CS2 Value = 1707 decimal
The CS2 circuit is now trimmed. The OCP limits and settings
should be configured after the current sense trim is performed.
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