ADP5080 datasheet(22/64 Pages) AD

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ADP5080

Data Sheet

DC-TO-DC CONVERTER CHANNELS

The ADP5080 integrates five buck regulators and a configurable

buck only/buck boost regulator. These regulators can be configured

for various functions including auto PSM, auto DCM, DVS, and

gate scaling. Each function is included only in the channels where

it is most effective (see Table 9).

Channel 1, Channel 2, and Channel 3: Buck Regulators

with Flex-Mode Architecture

Channel 1, Channel 2, and Channel 3 feature Flex-Mode™ current

mode control, which eliminates minimum on time requirements

and allows duty cycles as low as 0%. Flex-Mode uses a unique

adaptive control architecture that maintains stable operation over

a wide range of application conditions. With Flex-Mode control,

very high step-down ratios can be achieved while maintaining

high efficiency and excellent transient performance.

Selecting the Output Voltage, Channel 1 to Channel 3

The output voltage of Channel 1, Channel 2, or Channel 3 is

selected from one of the preset values available in the VIDx bits,

where x is 1, 2, or 3 (see Table 39 and Table 41). The default

output voltage value is factory fuse programmed.

Channel 3 has an adjustable mode option that can be selected

using the VID3 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). Channel 1

can also be used in adjustable output mode by setting the VID1

bits to 0.8 V and using external feedback resistors with values less

than 1 kΩ. When using the adjustable mode for Channel 1 or

Channel 3, be aware of the minimum off time restriction, which

may limit the range of available output voltages.

Channel 1, Channel 2, and Channel 3 are designed for very low

duty cycle operation. However, at very high duty cycle, these chan-

nels have a limited range due to the minimum off time restriction

(see Table 3). The minimum input voltage capability for a given

output voltage can be determined using the following equation:

VIN_MIN = VOUT/(1 − tOFF_MIN × fSW)

If the input voltage falls below this level, the output voltage

droops below its nominal value.

Current-Limit Protection, Channel 1 to Channel 3

Channel 1, Channel 2, and Channel 3 use valley mode current

limit (see Figure 38). In valley mode current-limit protection,

inductor current is sensed during the low-side on cycle, imme-

diately before the high-side FET turns on. If the inductor current is

above the current-limit threshold at this point, the next switching

pulse is skipped.

Figure 38. Valley Mode Current Limit

Switching does not resume until the current falls below the limit

threshold. This behavior creates an inherent frequency foldback

feature, which makes valley mode current-limit protection very

robust against runaway inductor current. Because this type of

current limit senses current before switching, it is also relatively

immune to switching noise.

Table 3 provides the valley current threshold specifications. The

actual load current-limit threshold varies with inductor value,

frequency, and input and output voltage.

When the current-limit threshold is exceeded, load current is not

allowed to increase further. Therefore, as the load impedance is

reduced, the current limit forces the output voltage to fall. The

falling output voltage in turn toggles the PWRGx, UVx,

and FAULT error flags.

In the extreme event of an output voltage short circuit, the UVP

function protects the device against excessive current during the

on cycle (see the Undervoltage Protection (UVP) section).

Table 9. DC-to-DC Converter Specifications and Functions

Channel

Regulator

Type

VIN Range (V)

VOUT Range (V)

Adjustable

Mode (V)

IOUT (A)

Auto

PSM

Auto

DCM

DVS

Gate

Scaling

Buck

4 to 15

0.8 to 1.21

0.8 to 1.2

Yes

N/A

Yes

Buck

4 to 15

1.0 to 3.3

N/A

1.15

Yes

N/A

Yes

N/A

Buck

4 to 15

1.2 to 1.8

0.8 to 3.6

1.5

Yes

N/A

Buck

4 to 15

1.8 to 3.55

1.0 to 5.0

0.8

Yes

N/A

Buck

4 to 15

3.0 to 5.0

N/A

Yes

N/A

Buck or

buck boost

4 to 15

3.5 to 5.5

1.0 to 5.0

2 (buck)

1.5 (buck

boost)

Yes

N/A

Channel 1 has two available voltage ranges.

VALLEY CURRENT-

LIMIT THRESHOLD

SW NODE

INDUCTOR CURRENT

CURRENT

SENSING

POINT

SKIPPED

CYCLE

Rev. A | Page 22 of 64

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