ADP1046AACPZ-R7 datasheet(33/88 Pages) AD

33 / 88 page

Data Sheet

ADP1046A

Rev. 0 | Page 33 of 88

POWER SUPPLY CALIBRATION AND TRIM

The ADP1046A 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 ADP1046A GUI allows the

user to automatically revert the trim settings to their factory

default values.

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 ADP1046A allows the user enough trim capability to trim

for external components with a tolerance of 0.5% or better. If

the ADP1046A 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.

CS1 TRIM

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 (RCS1) 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) × RCS1

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.

CS2 TRIM

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

package.

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

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 ADP1046A can trim for sense resistors with a

tolerance of 1% or better.

1. Apply a known load current (IOUT) 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 = IOUT × RSENSE/FS × 4096

where:

FS is the full-scale voltage drop (120 mV or 60 mV).

RSENSE is the sense resistor value.

If CS2 is programmed to the 120 mV range and IOUT = 10 A,

RSENSE = 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 IOUT = 5 A,

RSENSE = 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.

ADP1046AACPZ-R7 数据表(PDF) 33 Page - Analog Devices

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