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Data Sheet

ADP5052

Rev. 0 | Page 19 of 40

Phase Shift

The phase shift between Channel 1 and Channel 2 and between

Channel 3 and Channel 4 is 180°. Therefore, Channel 3 is in phase

with Channel 1, and Channel 4 is in phase with Channel 2 (see

Figure 40). This phase shift maximizes the benefits of out-of-phase

operation by reducing the input ripple current and lowering the

ground noise.

CH2

CH1

(½

fSW

OPTIONAL)

CH4

180° PHASE SHIFT

0° REFERENCE

0° PHASE SHIFT

180° PHASE SHIFT

CH3

(½

fSW

OPTIONAL)

Figure 40. Phase Shift Diagram, Four Buck Regulators

SYNCHRONIZATION INPUT/OUTPUT

The switching frequency of the ADP5052 can be synchronized

to an external clock with a frequency range from 250 kHz to

1.4 MHz. The ADP5052 automatically detects the presence

of an external clock applied to the SYNC/MODE pin, and the

switching frequency transitions smoothly to the frequency of

the external clock. When the external clock signal stops, the

device automatically switches back to the internal clock and

continues to operate.

Note that the internal switching frequency set by the RT pin must

be programmed to a value that is close to the external clock value

for successful synchronization; the suggested frequency differ-

ence is less than ±15% in typical applications.

The SYNC/MODE pin can be configured as a synchronization

clock output by factory fuse. A positive clock pulse with a 50%

duty cycle is generated at the SYNC/MODE pin with a frequency

equal to the internal switching frequency set by the RT pin. There

is a short delay time (approximately 15% of tSW) from the generated

synchronization clock to the Channel 1 switching node.

Figure 41 shows two ADP5052 devices configured for frequency

synchronization mode: one ADP5052 device is configured as

the clock output to synchronize another ADP5052 device. It is

recommended that a 100 kΩ pull-up resistor be used to prevent

logic errors when the SYNC/MODE pin is left floating.

ADP5052

100kΩ

VREG

SYNC/MODE

ADP5052

Figure 41. Two ADP5052 Devices Configured for Synchronization Mode

In the configuration shown in Figure 41, the phase shift between

Channel 1 of the first ADP5052 device and Channel 1 of the second

ADP5052 device is 0˚ (see Figure 42).

CH3 5.00V BW

CH1 2.00V BW

CH2 5.00V BW

M400ns

A CH1

560mV

SW1

AT FIRST

ADP5052

SW1

AT SECOND

ADP5052

SYNC-OUT

AT FIRST

ADP5052

Figure 42. Waveforms of Two ADP5052 Devices Operating

in Synchronization Mode

SOFT START

The buck regulators in the ADP5052 include soft start circuitry

that ramps the output voltage in a controlled manner during

startup, thereby limiting the inrush current. The soft start time

is typically fixed at 2 ms for each buck regulator when the SS12

and SS34 pins are tied to VREG.

To set the soft start time to a value of 2 ms, 4 ms, or 8 ms, connect

a resistor divider from the SS12 or SS34 pin to the VREG pin and

ground (see Figure 43). This configuration may be required to

accommodate a specific start-up sequence or an application with

a large output capacitor.

LEVEL DETECTOR

AND DECODER

VREG

TOP

RESISTOR

BOTTOM

RESISTOR

SS12

SS34

ADP5052

Figure 43. Level Detector Circuit for Soft Start

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