ADP1052ACPZ-R7 datasheet(33/113 Pages) AD

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Data Sheet

ADP1052

Rev. B | Page 33 of 113

VOLTAGE READINGS

Input Voltage Reading

The input voltage, which is reported in the READ_VIN command

(Register 0x88), is updated every 10 ms. The VIN_SCALE_

MONITOR command (Register 0xD8) is set for correct input

voltage reading.

The input voltage is sensed through the VF pin (Pin 5). The

VF ADC has an input range of 1.6 V. The raw data is stored in

is 1.6 V/2048 = 781.25 μV.

Because the input voltage signal can be sensed through the

switching node of the secondary windings, the voltage drop

caused by the conduction current in the primary switches,

transformer windings, and copper trace adds to the error to

the input voltage sense. To compensate for the error, use the

following equation:

YCOMP = YUNCOMP ± (N × X ÷ 211)

where:

YCOMP is the compensated VF value in Register 0xFEAC[15:5].

YUNCOMP is the uncompensated VF value in Register 0xFEAC[15:5].

N is the compensation coefficient set in Register 0xFE59[7:0],

and the polarity is set in Register 0xFE58[0].

X is the CS1 current value in Register 0xFEA7[15:4].

The compensated VF value is used for conversion of the

READ_VIN value.

Output Voltage Reading

The output voltage is reported in the READ_VOUT command

(Register 0x8B) and updated every 10 ms. The VOUT_SCALE_

MONITOR command (Register 0x2A) is programmed for correct

output voltage reading.

The output voltage value register (Register 0xFEAA) is updated

every 10 ms via the VS low frequency ADC.

The VS low frequency ADC has an input range of 1.6 V. The raw

data is stored in Register 0xFEAA. The reading is 12 bits, which

means that the LSB size is 1.6 V/4096 = 390.625 μV.

CURRENT READINGS

By default, the current readings are updated every 10 ms; however,

63 ms, 126 ms, 252 ms, or 504 ms.

Input Current Reading

The input current is reported in the READ_IIN command

(Register 0x89). The IIN_SCALE_MONITOR command

(Register 0xD9) is set for correct input current reading.

The input current reading is derived from the CS1 ADC, which has

an input range of 1.6 V. The raw data is stored in Register 0xFEA7.

The reading is 12 bits, which means that the LSB size is 1.6 V/

4096 = 390.625 μV.

Output Current Reading

The output current is reported in the READ_IOUT command

(Register 0x8C). The IOUT_CAL_GAIN command (Regis-

ter 0x38) is programmed for correct output current reading.

The output current reading is derived from the CS2 ADC reading.

The CS2 ADC has an input value range of 120 mV. The raw data

is stored in Register 0xFEA8. The reading is 12 bits, which means

that, within a 120 mV range, the LSB size is 120 mV/4096 =

29.297 μV.

CS3 Current Reading

The CS3 reading is an alternative output current reading that is

calculated using the CS1 reading and the duty cycle values. The

CS3 reading can be used as an alternate output current reading

and protection when the current sense resistor, which provides

the output current signal to CS2, is not used. Derive the output

current reading from the following equation:

IOUT = ICS3 × n

where ICS3 is read from Register 0xFEA9, and n is the turn ratio

of the main transformer (n = NPRI/NSEC).

Each LSB size in Register 0xFEA9 is 4× the LSB size of the CS1

reading in Register 0xFEA7. For example, if 1 LSB = 0.1 A in

POWER READINGS

Input Power Reading

The input power value (Register 0xFEAE) is the product of the

VF voltage value in Register 0xFEAC[15:5] and the CS1 current

value in Register 0xFEA7[15:4]. Therefore, a combination of both

voltage and current formulas is used to calculate the power reading

in watts (W). Register 0xFEAE is a 16-bit word. It multiplies two

12-bit numbers and then discards the eight LSBs.

Example: if 1 LSB in Register 0xFEAC[15:5] is 0.01 V and 1 LSB

in Register 0xFEA7[15:4] is 0.01 A, 1 LSB in Register 0xFEAE[15:0]

is 0.01 V × 0.01 A × 28 = 0.0256 W.

Output Power Reading

The output power value (Register 0xFEAF) is the product of the VS

voltage value in Register 0xFEAA[15:4] and the CS2 current value

in Register 0xFEA8[15:4]. Therefore, a combination of both

voltage and current formulas is used to calculate the power

reading in watts. Register 0xFEAF is a 16-bit word. It multiplies

two 12-bit numbers and then discards the eight LSBs.

Example: if 1 LSB in Register 0xFEAA[15:4] is 0.01 V and 1 LSB

in Register 0xFEA8[15:4] is 0.01 A, 1 LSB in Register 0xFEAF[15:0]

is 0.01 V × 0.01 A × 28 = 0.0256 W.

Alternately, the PMBus command READ_POUT (0x96) can be

used, which returns the output power (in watts) in linear data

format. Use Register 0xFE65[2:0] to select the update rate of 10 ms,

63 ms, 126 ms, 252 ms, or 504 ms.

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