ADP1046AACPZ-R7 datasheet(31/88 Pages) AD

31 / 88 page

Data Sheet

ADP1046A

Rev. 0 | Page 31 of 88

UNDERVOLTAGE PROTECTION (UVP)

If the voltage sensed at the VS1 pin falls below the program-

mable UVP threshold, the UVP flag is set. The UVP threshold

is programmed in Register 0x34; the GUI can also be used, as

shown in Figure 42.

The response to the UVP flag is programmable in Register

0x0B[3:0]. Undervoltage protection and the UVP flag are

disabled during soft start.

AC SENSE (ACSNS)

The ACSNS circuit performs multiple monitoring and control

functions. Two ADCs and a fast comparator are connected to

this pin.



The fast ADC is used for the voltage feedforward function

(see the Voltage Line Feedforward and ACSNS section).

This ADC has an equivalent resolution of 11 bits at 10 μs.



The slow ADC is used to report the input voltage. This

ADC has a resolution of 12 bits at 10 ms.



The fast comparator is used to monitor whether a

switching waveform is present at the output of the

synchronous rectifier stage (or rectifier diodes).

The pick-off point upstream of the output inductor is connected

to the ACSNS pin through an external RCD divider network.

The output of the ACSNS slow ADC is a 12-bit value reported

in Register 0x14. The gain of this ADC can be adjusted using

voltage spike.

The equation to calculate the ADC code is given by the

following formula:

ADC Code = Vx/1.6 × 4096

where Vx is the voltage at the ACSNS pin.

For example, when there is 1 V on the input of the ADC

ADC Code = 1 V/1.6 × 4096

ADC Code = 2560

VSENSE = (Vx) × (R1 + R2)/R2

where VSENSE is the filtered secondary voltage.

The primary input voltage can be calculated by multiplying

VSENSE by the turns ratio (N1/N2) as follows:

VPRIMARY = Vx × (R1 + R2)/R2 × (N1/N2)

The ACSNS comparator threshold is set at 0.45 V. If the average

voltage on the ACSNS pin falls below this threshold, the ACSNS

flag is set in Register 0x03[2] and in Register 0x07[2] (real-time

and latched flag registers, respectively), and the programmed

action for the flag is executed.

When operating in resonant mode, the ACSNS comparator is

used for the timing of the synchronous rectifiers and, therefore,

the additional features of the ADC cannot be used. For more

information, see the Resonant Mode Operation section.

Figure 42. Voltage Sense Window in Simulation Mode (ADP1046A GUI)

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