ADP5080 datasheet(24/64 Pages) AD

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ADP5080

Data Sheet

Channel 4 and Channel 5: Current Mode Buck Regulators

Channel 4 and Channel 5 are internally compensated current

mode control buck regulators (see Figure 41). Combined with

the integrated charge pump, these channels are designed to

operate at high duty cycles up to 100%.

Selecting the Output Voltage, Channel 4 and Channel 5

The output voltage of Channel 4 or Channel 5 is selected from

one of the preset values available in the VIDx bits, where x is 4

or 5 (see Table 43). The default output voltage value is factory

fuse programmed.

Channel 4 has an adjustable mode option that can be selected

using the VID4 bits. When the adjustable output voltage mode

is selected, the output voltage is set by an external feedback

resistor divider. Select resistor values such that the desired output

voltage is divided down to 0.8 V and the paralleled resistance

seen from the dividing node does not exceed 25 kΩ (see the

Setting the Output Voltage (Adjustable Mode Channels) section).

When using the adjustable mode for Channel 4, be aware of the

minimum on time restriction, which may limit the range of

available output voltages.

Channel 4 and Channel 5 are designed for very high duty cycle

operation. However, at very low duty cycle, these channels have

a limited range due to the minimum on time restriction (75 ns

typical) inherent in current mode control. The maximum input

voltage capability for a given output voltage can be determined

using the following equation:

VIN_MAX = VOUT/(tON_MIN × fSW)

If the input voltage rises above this level, the output voltage

continues to be regulated; however, switching pulses are skipped,

which may increase output voltage ripple.

Figure 41. Buck Regulator Block Diagram: Channel 4 and Channel 5

PVINx

SWx

PGNDx

FBx

PGND

PGNDx

4V TO 15V

POWER-GOOD

COMPARATOR

SOFT START

FB5

SW4

ERROR AMP

VREF

PWM

COMPARATOR

PGNDx

CURRENT

SENSE AMP

BSTx

VDRx

VREG1

PGNDx

OVP

UVP

OCP

SEQUENCER

LATCH

PSM LOGIC

ZERO CROSS

COMPARATOR

DISCHARGE

SWITCH

BSTCP

CURRENT

LIMIT

OCP

SLOPE

COMPENSATION

CLOCK

OUTPUT

VOLTAGE

OUTPUT

VOLTAGE

FB4

0.8V

EXTERNAL

VOLTAGE DIVIDER

(CH4 ADJ MODE ONLY)

ADP5080

Rev. A | Page 24 of 64

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