ADP1046ACPZ-R7 datasheet(88/96 Pages) AD

88 / 96 page

ADP1046

Data Sheet

Rev. 0 | Page 88 of 96

ADJUSTING THE TIMING OF THE PWM OUTPUTS

To accurately adjust the timing of the PWM outputs, the

following registers can be used to set the dead time and delays

of the PWM outputs: Register 0x41, Register 0x43, Register 0x45,

Refer to the Resonant Mode Register Descriptions section for

more information. The software GUI for the ADP1046 can be

used to set the frequency limit registers, as well as all other

settings related to the resonant mode of operation.

FREQUENCY LIMIT SETTING

The minimum frequency is set by Register 0x42 and the first

four bits of Register 0x44.

For example, Register 0x42 is set to 0xA0 (160 decimal) and

Bits[7:4] of Register 0x44 are set to 0xF (15 decimal).

The maximum switching cycle is

(160 × 16 + 15) × 5 ns = 12.875 μs

The lowest switching frequency limit is

1/12.875 μs = 77.7 kHz

The maximum frequency is set by Register 0x46 and by

Bits[7:4] of Register 0x48.

For example, Register 0x46 is set to 0x10 (16 decimal) and

Bits[7:4] of Register 0x48 are set to 0x9 (9 decimal).

The minimum switching cycle is

(16 × 16 + 9) × 5 ns = 1.325 μs

The highest switching frequency limit is

1/1.325 μs = 755 kHz

FEEDBACK CONTROL IN RESONANT MODE

In contrast to a traditional fixed frequency PWM converter, the

output voltage of a resonant converter is regulated by changing

the switching frequency. When the ADP1046 is operated in

resonant mode, the switching frequency decreases when the

sensed voltage is lower than the reference voltage. This makes

the ADP1046 capable of controlling a resonant converter in

zero-voltage switching (ZVS) mode.

Although the switching frequency is variable, the high

frequency feedback voltage sampling frequency (VS3± pins)

is fixed at 400 kHz. The parameters of the feedback filter are

based on this frequency. The method for calculating the filter

parameters (gains, zeros, and poles) is the same as that for the

fixed frequency PWM mode (see the Digital Filter section).

SOFT START IN RESONANT MODE

During soft start, the reference voltage of the ADP1046 ramps

up. With the feedback loop closed, the switching frequency is

reduced from the highest limit to a regulation value. The soft

start timing settings and the filter settings are the same as those

for the fixed frequency PWM mode (see the Soft Start section).

LIGHT LOAD OPERATION (BURST MODE)

To control the converter at very light load, the ADP1046 can

operate in burst mode. Burst mode can be enabled or disabled

using Bits[7:6] of Register 0x4A. When the desired switching

frequency is higher than the burst mode threshold, the part

enters burst mode. The threshold is determined by the maxi-

mum frequency and the burst mode offset setting.

The threshold value used to enter burst mode is determined as

follows:

Threshold value for burst mode =

((Register 0x46 × 16) + Register 0x48[7:4]) +

(Register 0x4A[5:0] × 2)

The threshold value used to exit burst mode is determined by

the entrance value plus 0x10.

For example, Register 0x46 is set to 0x10 (16 decimal), Bits[7:4]

of Register 0x48 are set to 0, and Bits[5:0] of Register 0x4A are

set to 0x8 (8 decimal).

The minimum switching cycle is

(16 × 16 + 0) × 5 ns = 1.28 μs

The highest switching frequency limit is

1/1.28 μs = 781 kHz

The threshold to enter burst mode is

[(16 × 16 + 0) + (8 × 2)] × 5 ns = 1.36 μs

When the desired switching frequency is higher than

1/1.36 μs = 735 kHz, the PWM outputs are shut down

and the part enters burst mode.

The threshold to exit burst mode is

[(16 × 16 + 0) + (8 × 2) + 16] × 5 ns = 1.44 μs

Therefore, when the desired switching frequency becomes lower

than 1/1.44 μs = 694 kHz, the PWM signals are reenabled, and

the part exits burst mode.

OUTAUX IN RESONANT MODE

In resonant mode, the OUTAUX pin cannot be used as a control

signal. However, OUTAUX can be used as a fixed frequency

PWM signal with a fixed duty cycle.

PROTECTIONS IN RESONANT MODE

All of the flags and protections that are available in resonant mode

behave in the same manner as in fixed frequency PWM mode.

ADP1046ACPZ-R7 数据表(PDF) 88 Page - Analog Devices

ADP1046ACPZ-R7 数据表(HTML) 88 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

数据表下载