ADP5080 datasheet(21/64 Pages) AD

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Data Sheet

ADP5080

LDO2

LDO2 regulates the internally routed VREG2 pin voltage to 3 V,

3.15 V, 3.2 V, or 3.3 V and is capable of providing up to

300 mA. LDO2 internally supplies the control block of the

ADP5080, as well as external circuits supplied through the

VREG2 pin.

The LDO2 output is enabled when the VBATT pin voltage rises

above the UVLO threshold and is disabled when the VBATT

pin voltage falls below the UVLO threshold.

VISW2 Input

A 3.0 V to 3.3 V regulator connected to the VISW2 pin can take

over from LDO2 to supply the internal circuit of the ADP5080 and

the VREG2 load. To enable this feature, set the SEL_INP_LDO2

bit (Bit 4 in Register 33) high after the VISW2 pin voltage settles

above 2.7 V.

If the VISW2 pin voltage falls below 2.55 V, LDO2 resumes

control automatically. However, if the VISW2 source is disabled,

it is recommended that the SEL_INP_LDO2 bit be reset to 0

before turning off the VISW2 pin source.

The use of an external regulator connected to the VISW2 pin is

intended to achieve better system power efficiency by allowing

a switching power supply to take over the LDO2 linear regulator

when the system is powered up to operation. If the VISW2 input

is not used, tie it to GND. The VISW2 input is not active until

EN is high.

Because the VISW2 input supplies VREG2 with no regulation,

the maximum voltage that can be applied to VISW2 is 3.3 V. The

VISW2 input has a relatively high resistance compared to the

LDO2 path. As a result, VISW2 regulation may not be sufficient

when used to supply heavier loads.

Current Limit for LDO2

LDO2 is rated to a maximum load current of 300 mA. Above

this level, the current-limit feature limits the current to protect

the device.

The VISW2 input has an independent current-limit circuit with

a typical threshold of 300 mA. If this overcurrent threshold is

exceeded, the VISW2 input is immediately disconnected and

LDO2 takes over to supply the VREG2 current. After the VISW2

input is turned off due to a current-limit event, it can be reset

only by toggling the EN pin.

Discharge Switch for LDO2

A discharge switch at the VREG2 pin turns on during low

VBATT pin voltage (3.5 V ± 0.1 V hysteresis), removing the

residual charge of the external capacitor via a 12 Ω resistor.

Figure 37. VREG2, LDO2, and VISW2

CURRENT

DETECTION

VISW2

VREG2

AGND

FROM VREG1

OUTPUT

5.0V TO 5.5V

LDO2

VREF

OVERCURRENT

PROTECTION

DISCHARGE

SWITCH

INTERNAL

CIRCUITS

3.0V TO 3.3V

VOLTAGE

DETECTION

OVERCURRENT

PROTECTION

Rev. A | Page 21 of 64

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