LOADSW/LDO — Load switches/LDO regulators

Two load switches are available for use as switches or LDOs. 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.

Load switch

The load switches are OFF by default and can be controlled through a control register or GPIO pin using the following bits.

Control register bits for each load switch:
- TASK.LDSW[n]SET
- TASK.LDSW[n]CLR
GPIO[n], once configured by host software:
- LDSW[n]GPISEL

When a GPIO is configured as a load switch, it uses edges. When the GPIO toggles from LOW to HIGH, the switch turns ON (conducting). When the GPIO toggles from HIGH to LOW, the switch turns OFF.

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

Soft start circuitry is enabled by host software and is adjustable. The soft start current limit can be set in register LDSWCONFIG. A pull-down resistor R_LSPD on the LSOUT[n] pin is enabled in a register bit. See register LDSWCONFIG.

LDO mode

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

The LDO can be supplied from BUCK or VSYS, but must comply with VIN_LDO.

Electrical specification

Table 1. LOADSW electrical specification
Symbol	Description	Min.	Typ.	Max.	Unit
RDSON_LS	Switch on-resistance LS_IN = 3.3 V		200		mΩ
I_LS	Current LS_OUT ≥ 1.2 V			100	mA
t_SS	Soft start time Soft start current limit = 25 mA, 10 µF, 0 V to 5 V		1.8		ms
R_LSPD	Pull-down resistor (active discharge) at LS_OUT		2		kΩ
VIN_LS	Input voltage range	1.0		VSYS	V

Table 2. LDO electrical specification
Symbol	Description	Min.	Typ.	Max.	Unit
IOUT_LDO	Output current VOUT > 1.2 V			50	mA
IOUT_LDO	Output current VOUT < 1.2 V			10	mA
VIN_LDO	Input voltage range	2.6		VSYS	V
VOUT_LDO	Minimum setting output voltage		1.0		V
VOUT_LDO	Maximum setting output voltage		3.3		V
VOUT_LDO step	Output voltage step size		100		mV

Electrical characteristics

The following graphs show typical electrical characteristics for LOADSW.

Figure 1. LOADSW RDS_ON vs. junction temperature

The following graphs show electrical characteristics for LDO.

Figure 2. LDO voltage accuracy vs. junction temperature (VBUS = 5.5 V)

Figure 3. LDO voltage accuracy vs. junction temperature (VBAT = 3.8 V)

Figure 4. LDO dropout vs. junction temperature

Figure 5. VINLDO = 3.8 V: VOUTLDO = 1.8 V: LDO load transient

Registers

Instances

Instance	Base address	Description
LDSW	0x00000800	LOADSW registers LDSW register map

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 Status
LDSW1GPISEL	0x5	Load Switch1 GPIO Control Select
LDSW2GPISEL	0x6	Load Switch2 GPIO Control Select
LDSWCONFIG	0x7	Load Switch Configuration
LDSW1LDOSEL	0x8	Load Switch1 / LDO Select
LDSW2LDOSEL	0x9	Load Switch2 / LDO Select
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			LDSW1_Enable request SET
			NOEFFECT	0	no effect
			SET	1	LDSW1 Enable request set

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			LDSW1_Enable request CLR
			NOEFFECT	0	no effect
			CLR	1	LDSW1 Disable request clr

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			LDSW2_Enable request SET
			NOEFFECT	0	no effect
			SET	1	LDSW2 Enable request set

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			LDSW2_Enable request CLR
			NOEFFECT	0	no effect
			CLR	1	LDSW2 Disable request clr

LDSWSTATUS

Address offset: 0x4

Load Switch 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			Current status of LDSW1
B	R	LDSW1PWRUPLDO			Current status of LDO1
C	R	LDSW2PWRUPLDSW			Current status of LDSW2
D	R	LDSW2PWRUPLDO			Current status of LDO1
E	R	LDSWENABLE			Status of LDSW[n] and LDO[n]

LDSW1GPISEL

Address offset: 0x5

Load Switch1 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 GPI controls Load Switch1
			NOTUSED1	0	no GPI selected
			GPIO0	1	GPI_0 selected
			GPIO1	2	GPI_1 selected
			GPIO2	3	GPI_2 selected
			GPIO3	4	GPI_3 selected
			GPIO4	5	GPI_4 selected
			NOTUSED2	6	no GPI selected
			NOTUSED3	7	no GPI selected
B	RW	LDSW1GPIINV			Invert the sense of the selected GPIO
			NORMAL	0	not Inverted
			INVERTED	1	Inverted

LDSW2GPISEL

Address offset: 0x6

Load Switch2 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 GPI controls Load Switch2
			NOTUSED1	0	no GPI selected
			GPIO0	1	GPI_0 selected
			GPIO1	2	GPI_1 selected
			GPIO2	3	GPI_2 selected
			GPIO3	4	GPI_3 selected
			GPIO4	5	GPI_4 selected
			NOTUSED2	6	no GPI selected
			NOTUSED3	7	no GPI selected
B	RW	LDSW2GPIINV			Invert the sense of the selected GPIO
			NORMAL	0	not Inverted
			INVERTED	1	Inverted

LDSWCONFIG

Address offset: 0x7

Load Switch 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			Load Switch1 Soft Start Disable
			NOEFFECT	0	no effect
			NOSOFTSTART	1	Soft Start Disabled
B	RW	LDSW2SOFTSTARTDISABLE			Load Switch2 Soft Start Disable
			NOEFFECT	0	no effect
			NOSOFTSTART	1	Soft Start Disabled
C	RW	LDSW1SOFTSTARTSEL			Select Soft Start level for Load Switch1
			10MA	0	10mA
			20MA	1	20mA
			35MA	2	35mA
			50MA	3	50mA
D	RW	LDSW2SOFTSTARTSEL			Select Soft Start level for Load Switch1
			10MA	0	10mA
			20MA	1	20mA
			35MA	2	35mA
			50MA	3	50mA
E	RW	LDSW1ACTIVEDISCHARGE			Load Switch1 Active discharge Enable
			NODISCHARGE	0	No Discharge
			ACTIVE	1	Active Discharge Enabled
F	RW	LDSW2ACTIVEDISCHARGE			Load Switch2 Active discharge Enable
			NODISCHARGE	0	No Discharge
			ACTIVE	1	Active Discharge Enabled

LDSW1LDOSEL

Address offset: 0x8

Load Switch1 / LDO Select

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 LDSW1 or LDO1
			LDSW	0	Load Switch
			LDO	1	LDO

LDSW2LDOSEL

Address offset: 0x9

Load Switch2 / LDO Select

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 LDSW2 or LDO2
			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			Low-dropout regulator 1 programmable output voltage
			1V	0	1V
			1V1	1	1.1V
			1V2	2	1.2V
			1V3	3	1.3V
			1V4	4	1.4V
			1V5	5	1.5V
			1V6	6	1.6V
			1V7	7	1.7V
			1V8	8	1.8V
			1V9	9	1.9V
			2V	10	2V
			2V1	11	2.1V
			2V2	12	2.2V
			2V3	13	2.3V
			2V4	14	2.4V
			2V5	15	2.5V
			2V6	16	2.6V
			2V7	17	2.7V
			2V8	18	2.8V
			2V9	19	2.9V
			3V	20	3V
			3V1	21	3.1V
			3V2	22	3.2V
			3V3	23	3.3V

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			Low-dropout regulator 2 programmable output voltage
			1V	0	1V
			1V1	1	1.1V
			1V2	2	1.2V
			1V3	3	1.3V
			1V4	4	1.4V
			1V5	5	1.5V
			1V6	6	1.6V
			1V7	7	1.7V
			1V8	8	1.8V
			1V9	9	1.9V
			2V	10	2V
			2V1	11	2.1V
			2V2	12	2.2V
			2V3	13	2.3V
			2V4	14	2.4V
			2V5	15	2.5V
			2V6	16	2.6V
			2V7	17	2.7V
			2V8	18	2.8V
			2V9	19	2.9V
			3V	20	3V
			3V1	21	3.1V
			3V2	22	3.2V
			3V3	23	3.3V