Two load switches are available for use as switches or LDO regulators (LDO). They have dedicated input pins where voltage cannot exceed VSYS. The input voltage can be equal to VOUT1, VOUT2, or any voltage up to the VSYS voltage.

The mode is selected using registers LDSW[n]LDOSEL.

The load switches (and LDOs) are OFF by default and can be controlled through control registers or GPIO pins using the following bits.

When a GPIO is used to control LOADSW/LDO, it uses edges. When the GPIO toggles from LOW to HIGH, LOADSW/LDO turns ON (switch conducting). When the GPIO toggles from HIGH to LOW, LOADSW/LDO turns OFF.

Each load switch or LDO can be assigned to a separate GPIO, or a single GPIO can control both switches or LDOs.

A pull-down resistor RLSPD on the LSOUT[n] pin is enabled in a register bit for LOADSW/LDO. See register LDSW.LDSWCONFIG.

Load switch mode

Soft start is enabled by default. This ensures that the current to LSOUT[n] is limited for tSS. Once soft start is complete, there will be no current limiting provided by the load switch. Current limiting is only available from the power source connected to LSIN[n].

The soft start current limit for a load switch can be set in register LDSW.LDSWCONFIG.

LDO mode

The load switches can be independently configured as LDOs. The LDO output voltage is configurable in registers LDSW[n]VOUTSEL.

The LDO can be supplied from VOUT1, VOUT2 or VSYS, but must comply with VINLDO.

Electrical specification

Table 1. LOADSW electrical specification
Symbol Description Min. Typ. Max. Unit
RDSONLS

Switch on-resistance

LSIN = 3.3 V

200
ILS

Current

LSOUT ≥ 1.2 V

100 mA
tSS

Soft start time

Soft start current limit = 25 mA, 10 µF, 0 V to 5 V

1.8 ms
RLSPD Pull-down resistor (active discharge) at LSOUT 2
VINLS Input voltage range 1.0 VSYS V
IQLS Additional quiescent current from VBAT when load switch is enabled (VBAT = 3.8 V, VINLS = VSYS, ILOAD = 0, VBUS disconnected, both BUCKs running in Hysteretic mode) 60 nA
Table 2. LDO electrical specification
Symbol Description Min. Typ. Max. Unit
IOUTLDO Output current VOUT > 1.2 V 50 mA
IOUTLDO Output current VOUT < 1.2 V 10 mA
VINLDO Input voltage range 2.6 VSYS V
VOUTLDO Minimum setting output voltage 1.0 V
VOUTLDO Maximum setting output voltage 3.3 V
VOUTLDO_STEP Output voltage step size 100 mV
VOUTACC DC output voltage accuracy

(VINLDO = 3.8 V to 5.5 V, ILOAD = 1 mA)

±3 %
LINEREG_LDO DC line regulation

(VOUTLDO = 1.0 V, VINLDO = 3 V to 5.5 V, ILOAD = 1 mA)

2 mV/V
DC line regulation

(VOUTLDO = 1.8 V, VINLDO = 3 V to 5.5 V, ILOAD = 1 mA)

4 mV/V
DC line regulation

(VOUTLDO = 3.3 V, VINLDO = 3.7 V to 5.5 V, ILOAD = 1 mA)

11 mV/V
LOADREG_LDO DC load regulation

(VOUTLDO = 1 V to 1.2 V, VINLDO = 3.8 V, ILOAD = 50 μA to 10 mA)

0.4 mV/mA
DC load regulation

(VOUTLDO = 1.8 V to 3.3 V, VINLDO = 3.8 V, ILOAD = 50 μA to 50 mA)

0.25 mV/mA
PSRR Power supply rejection ratio

(VOUTLDO = 3 V, VINLDO = 3.8 V, ILOAD = 20 mA, f = 1 kHz)

50 dB
VRIPPLE Output voltage ripple in ULP mode

(VBUS disconnected, both BUCKs running in Hysteretic mode, VOUTLDO = 1.8 V, VINLDO = 3.8 V, ILOAD = 1 mA)

17 mVp-p
Output voltage ripple in ULP mode

(VBUS disconnected, both BUCKs running in Hysteretic mode, VOUTLDO = 3.3 V, VINLDO = 3.8 V, ILOAD = 1 mA)

35 mVp-p
LDODROPOUT Dropout voltage

VOUTLDO = 3.3 V, ILOAD = 50 mA

25 mV
IQLDO Additional quiescent current from VBAT when LDO is enabled (VBAT = 3.8 V, VINLDO = VSYS, ILOAD = 0, VBUS disconnected, both BUCKs running in Hysteretic mode) 500 nA
Additional quiescent current from VBAT when LDO is enabled (VBAT = 3.8 V, VINLDO = VSYS, ILOAD = 0, VBUS disconnected, both BUCKs running in PWM mode) 10 μA

Electrical characteristics

The following graphs show typical electrical characteristics for LOADSW.

Figure 1. LOADSW RDSON vs. junction temperature
LOADSW RDSON vs junction temperature

The following graphs show electrical characteristics for LDO.

Figure 2. LDO voltage accuracy vs. junction temperature (VBUS = 5.5 V)
LDO voltage accuracy vs junction temperature
Figure 3. LDO voltage accuracy vs. junction temperature (VBAT = 3.8 V)
LDO voltage accuracy vs junction temperature
Figure 4. LDO dropout vs. junction temperature
LDO dropout vs junction temperature
Figure 5. VINLDO = 3.8 V: VOUTLDO = 1.8 V: LDO load transient
VINLDO = 3.8 V: VOUTLDO = 1.8 V: LDO load transient
Figure 6. VOUTLDO = 1.8 V or 3.0 V: Leakage current vs. junction temperature (no load)

VOUTLDO = 1.8 V or 3.0 V: Leakage current vs. junction temperature (no load)

Registers

Instances

Instance Base address Description
LDSW 0x00000800

LOADSW registers

LDSW register map

Register overview

Register Offset Description
TASKLDSW1SET 0x0

Enable LDSW1

TASKLDSW1CLR 0x1

Disable LDSW1

TASKLDSW2SET 0x2

Enable LDSW2

TASKLDSW2CLR 0x3

Disable LDSW2

LDSWSTATUS 0x4

Load switch and LDO status

LDSW1GPISEL 0x5

LDSW1 GPIO control select

LDSW2GPISEL 0x6

LDSW2 GPIO control select

LDSWCONFIG 0x7

Load switch or LDO configuration

LDSW1LDOSEL 0x8

Select LDSW1 mode

LDSW2LDOSEL 0x9

Select LDSW2 mode

LDSW1VOUTSEL 0xC

LDO1 programmable output voltage

LDSW2VOUTSEL 0xD

LDO2 programmable output voltage

TASKLDSW1SET

Address offset: 0x0

Enable LDSW1

Bit number 7 6 5 4 3 2 1 0
ID A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

W

TASKLDSW1SET

Set LDSW1 enable

NOEFFECT

0

No effect

SET

1

Set enable

TASKLDSW1CLR

Address offset: 0x1

Disable LDSW1

Bit number 7 6 5 4 3 2 1 0
ID A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

W

TASKLDSW1CLR

Clear LDSW1 enable

NOEFFECT

0

No effect

CLR

1

Clear enable

TASKLDSW2SET

Address offset: 0x2

Enable LDSW2

Bit number 7 6 5 4 3 2 1 0
ID A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

W

TASKLDSW2SET

Set LDSW2 enable

NOEFFECT

0

No effect

SET

1

Set enable

TASKLDSW2CLR

Address offset: 0x3

Disable LDSW2

Bit number 7 6 5 4 3 2 1 0
ID A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

W

TASKLDSW2CLR

Clear LDSW2 enable

NOEFFECT

0

No effect

CLR

1

Clear enable

LDSWSTATUS

Address offset: 0x4

Load switch and LDO status

Bit number 7 6 5 4 3 2 1 0
ID E D C B A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

R

LDSW1PWRUPLDSW

Load switch 1 status

OFF

0

OFF

ON

1

ON

B

R

LDSW1PWRUPLDO

LDO1 status

OFF

0

OFF

ON

1

ON

C

R

LDSW2PWRUPLDSW

Load switch 2 status

OFF

0

OFF

ON

1

ON

D

R

LDSW2PWRUPLDO

LDO2 status

OFF

0

OFF

ON

1

ON

E

R

LDSWENABLE

LDSW1 or LDSW2 in use

OFF

0

OFF

ON

1

ON

LDSW1GPISEL

Address offset: 0x5

LDSW1 GPIO control select

Bit number 7 6 5 4 3 2 1 0
ID B A A A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

LDSW1GPISEL

Select which GPIO controls LDSW1

NOTUSED1

0

No GPIO selected

GPIO0

1

GPIO 0 selected

GPIO1

2

GPIO 1 selected

GPIO2

3

GPIO 2 selected

GPIO3

4

GPIO 3 selected

GPIO4

5

GPIO 4 selected

NOTUSED2

6

No GPIO selected

NOTUSED3

7

No GPIO selected

B

RW

LDSW1GPIINV

Invert the sense of the selected GPIO

NORMAL

0

Not inverted

INVERTED

1

Inverted

LDSW2GPISEL

Address offset: 0x6

LDSW2 GPIO control select

Bit number 7 6 5 4 3 2 1 0
ID B A A A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

LDSW2GPISEL

Select which GPIO controls LDSW2

NOTUSED1

0

No GPIO selected

GPIO0

1

GPIO 0 selected

GPIO1

2

GPIO 1 selected

GPIO2

3

GPIO 2 selected

GPIO3

4

GPIO 3 selected

GPIO4

5

GPIO 4 selected

NOTUSED2

6

No GPIO selected

NOTUSED3

7

No GPIO selected

B

RW

LDSW2GPIINV

Invert the sense of the selected GPIO

NORMAL

0

Not inverted

INVERTED

1

Inverted

LDSWCONFIG

Address offset: 0x7

Load switch or LDO configuration

Bit number 7 6 5 4 3 2 1 0
ID F E D D C C B A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

LDSW1SOFTSTARTDISABLE

LDSW1 soft start disable

NOEFFECT

0

No effect

NOSOFTSTART

1

Soft start disabled

B

RW

LDSW2SOFTSTARTDISABLE

LDSW2 soft start disable

NOEFFECT

0

No effect

NOSOFTSTART

1

Soft start disabled

C

RW

LDSW1SOFTSTARTSEL

Select soft start level for LDSW1

25MA

0

25 mA

50MA

1

50 mA

75MA

2

75 mA

100MA

3

100 mA

D

RW

LDSW2SOFTSTARTSEL

Select soft start level for LDSW2

25MA

0

25 mA

50MA

1

50 mA

75MA

2

75 mA

100MA

3

100 mA

E

RW

LDSW1ACTIVEDISCHARGE

LDSW1 active discharge enable

NODISCHARGE

0

No discharge

ACTIVE

1

Active discharge enabled

F

RW

LDSW2ACTIVEDISCHARGE

LDSW2 active discharge enable

NODISCHARGE

0

No discharge

ACTIVE

1

Active discharge enabled

LDSW1LDOSEL

Address offset: 0x8

Select LDSW1 mode

Bit number 7 6 5 4 3 2 1 0
ID A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

LDSW1LDOSEL

Select Load switch or LDO

LDSW

0

Load switch

LDO

1

LDO

LDSW2LDOSEL

Address offset: 0x9

Select LDSW2 mode

Bit number 7 6 5 4 3 2 1 0
ID A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

LDSW2LDOSEL

Select Load switch or LDO

LDSW

0

Load switch

LDO

1

LDO

LDSW1VOUTSEL

Address offset: 0xC

LDO1 programmable output voltage

Bit number 7 6 5 4 3 2 1 0
ID A A A A A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

LDSW1VOUTSEL

LDO1 programmable output voltage

1V

0

1.0 V

1V1

1

1.1 V

1V2

2

1.2 V

1V3

3

1.3 V

1V4

4

1.4 V

1V5

5

1.5 V

1V6

6

1.6 V

1V7

7

1.7 V

1V8

8

1.8 V

1V9

9

1.9 V

2V

10

2.0 V

2V1

11

2.1 V

2V2

12

2.2 V

2V3

13

2.3 V

2V4

14

2.4 V

2V5

15

2.5 V

2V6

16

2.6 V

2V7

17

2.7 V

2V8

18

2.8 V

2V9

19

2.9 V

3V

20

3.0 V

3V1

21

3.1 V

3V2

22

3.2 V

3V3

23

3.3 V

LDSW2VOUTSEL

Address offset: 0xD

LDO2 programmable output voltage

Bit number 7 6 5 4 3 2 1 0
ID A A A A A
Reset 0x00 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

LDSW2VOUTSEL

LDO2 programmable output voltage

1V

0

1.0 V

1V1

1

1.1 V

1V2

2

1.2 V

1V3

3

1.3 V

1V4

4

1.4 V

1V5

5

1.5 V

1V6

6

1.6 V

1V7

7

1.7 V

1V8

8

1.8 V

1V9

9

1.9 V

2V

10

2.0 V

2V1

11

2.1 V

2V2

12

2.2 V

2V3

13

2.3 V

2V4

14

2.4 V

2V5

15

2.5 V

2V6

16

2.6 V

2V7

17

2.7 V

2V8

18

2.8 V

2V9

19

2.9 V

3V

20

3.0 V

3V1

21

3.1 V

3V2

22

3.2 V

3V3

23

3.3 V