BUCK consists of two step-down buck regulators, BUCK1 and BUCK2.

BUCK has the following features:

  • Ultra-high efficiency (low IQ) and low noise operation
  • PWM and Hysteretic modes with automatic switching based on load
  • TWI configurable for forcing PWM mode to minimize output voltage ripple
  • Configurable output voltages between 1.0 V and 3.3 V

Hysteretic mode offers efficiency at lower load currents and typically operates up to half the maximum PWM current. PWM mode provides a clean supply operation due to a constant switching frequency, FBUCK. This provides optimal coexistence with RF circuits. BUCK can automatically change between Hysteretic and PWM modes.

Note: The outputs of BUCK1 and BUCK2 must not be tied together as they are not intended to operate in such configuration.

On/Off control

BUCK is enabled in the following ways.

  • VSET[n] pin
  • Control registers
  • GPIO[n] pin

The VSET1 and VSET2 pins are enabled only at power-on. If resistor RVSETn is present, BUCK is enabled with the output voltage defined by the resistor value. If the pin is grounded, BUCK is disabled. See Default VOUT1 using an external resistor and Default VOUT2 using an external resistor.

Control registers BUCK1ENASET, BUCK1ENACLR, BUCK2ENASET, and BUCK2ENACLR have enable and disable bits for each BUCK. These registers override the default BUCK state.

A GPIO can be configured in register BUCKENCTRL to enable or disable BUCK.

If BUCK is disabled during power up, the system defaults to software control of BUCK.

Output voltage selection

The output voltage range for BUCK is programmable with TWI. The default output voltage selection is found on pins VSET1 and VSET2, which are configured using an external resistor to GND. Only the output voltages shown in the tables can be selected using resistors. The VOUT[n] pins have two voltage configuration registers that are selectable through a GPIO pin with predefined voltage settings available.

The VSET[n] pins are effective only at start up. The external resistor (maximum 5% tolerance) defines the default output voltage setting as found in the following table.

Table 1. Default VOUT1 using an external resistor
Symbol Nominal resistance VOUT1 start up output voltage
RVSET1 <100 Ω (grounded) 0 V (OFF)
4.7 kΩ 1.0 V
10 kΩ 1.2 V
22 kΩ 1.5 V
47 kΩ 1.8 V
68 kΩ 2.0 V
100 kΩ 2.2 V
150 kΩ 2.5 V
250...500 kΩ 2.7 V
Table 2. Default VOUT2 using an external resistor
Symbol Nominal resistance VOUT2 start up output voltage
RVSET2 <100 Ω (grounded) 0 V (OFF)
4.7 kΩ 1.8 V
10 kΩ 2.0 V
22 kΩ 2.2 V
47 kΩ 2.4 V
68 kΩ 2.5 V
100 kΩ 2.7 V
150 kΩ 3.0 V
250...500 kΩ 3.3 V
Note: Do not leave VSET[n] floating, make sure that the VSET[n] pins have the correct configuration.

The output voltage range is from 1.0 V to 3.3 V in 100 mV steps and is set in the voltage configuration registers BUCK1NORMVOUT and BUCK2NORMVOUT. Once the voltage is selected, register BUCKSWCTRLSEL must be written to for the values to take effect.

Registers BUCK1VOUTSTATUS and BUCK2VOUTSTATUS indicate the status or current voltage setting.

A GPIO can be configured to select between two voltage levels. The output voltage for retention mode is configured in registers BUCK1RETVOUT and BUCK2RETVOUT. Select a GPIO to control retention voltage in register BUCKVRETCTRL.

BUCK mode selection

BUCK operates in Automatic mode by default. When in Automatic mode, BUCK selects Hysteretic mode for low load currents, and PWM mode for high load currents.

In PWM mode, BUCK provides a clean supply operation due to constant switching frequency and lower voltage ripple for optimal coexistence with RF circuits.

Forced pulse width modulation (PWM) is set by the following:

  • Control register bits in BUCK[n]PWMSET
  • GPIO[n] pins in register BUCKPWMCTRL overriding the register setting for one or both BUCKs

Hysteretic mode can be forced in register BUCKCTRL0 for each BUCK. This setting is not available using GPIO.

Active output capacitor discharge

When the converter is disabled, active discharge can be enabled or disabled in register BUCKCTRL0 using RDISCH from the output capacitors. The default setting is disabled.

Capacitor discharge is forced when there is a power cycle reset. See figure Power cycle.

Component selection

Recommended values for the inductor are shown in the following table.

Table 3. Recommended inductor specifications
Parameter Value Unit
Nominal inductance 2.2 μH
Inductor tolerance ≤ 20 %
DC resistance (DCR) ≤ 400 mΩ
Saturation current (Isat) > 350 mA
Rated current (Imax) > 200 mA
Table 4. Recommended capacitor specifications
Parameter Value Unit
Effective capacitance ≥ 4 μF
ESR ≤ 50 mΩ

Electrical specification

Table 5. BUCK electrical specification
Symbol Description Min. Typ. Max. Unit
VOUT[n]ACC Output voltage accuracy -5 +5 %
VSYSMIN Minimum VSYS voltage for enabling BUCK (dependent on POF setting) 2.7 V
IOUT Maximum BUCK current to maintain performance 200 mA
VDROP_OUT Drop-out voltage 1 mA load 100 mV
RDISCH Active output capacitor discharge resistance 2 kΩ
IPWMTHRES Load current threshold from Hysteretic to PWM mode (mode = AUTO) 90 mA
IHYSTTHRES Load current threshold from PWM to Hysteretic mode (mode = AUTO) 40 mA
VOUTRIPPLEPWM

VOUT ripple in PWM mode

IOUT = 200 mA

 5 mVpp
VOUTRIPPLEHYST VOUT ripple in Hysteretic mode 50 mVpp
EFFBUCK

Efficiency in PWM mode

VSYS = 3.8 V

VOUT = 3.3 V

IOUT = 200 mA

 93 %
fBUCK Switching frequency in PWM mode 3.6 MHz
tSTRT

Start-up time

VOUT = 3.3 V

C = 10 µF

 1.2 ms
tPWMMODE

Transition time

Hysteretic to PWM mode

Automatic (and via TWI or GPIO)

90

(55)

 μs
tHYST

Transition time

Hysteretic to PWM mode

Automatic (and through TWI or GPIO)

35

(25)

 μs

Electrical characteristics

The following graphs show typical electrical characteristics for BUCK.

Figure 1. VBAT = 4.35 V: VOUT = 3.0 V vs. junction temperature
VBAT = 4.35 V: VOUT = 3.0 V vs Junction Temperature
Figure 2. VBAT = 3.8: VOUT = 3.0 V vs. junction temperature
VBAT = 4.35 V: VOUT = 3.0 V vs Junction Temperature
Figure 3. VBAT = 4.35 V: VOUT = 1.8 vs. junction temperature
VBAT = 4.35 V: VOUT = 1.8 vs Junction Temperature
Figure 4. VBAT = 3.8 V: VOUT = 1.8 vs. junction temperature
VBAT = 3.8 V: VOUT = 1.8 vs Junction Temperature
Figure 5. VBAT = 3.8 V: VOUT = 2.0 V: PFM frequency vs. current
VBAT = 3.8 V: VOUT = 2.0 V: PFM frequency vs current
Figure 6. VBAT = 3.8 V: VOUT = 2.0 V: GPIO BUCK start
VBAT = 3.8 V: VOUT = 2.0 V: GPIO BUCK start
Figure 7. VBAT = 3.8 V: VOUT = 2.0 V: GPIO PWM mode selection
VBAT = 3.8 V: VOUT = 2.0 V: GPIO PWM mode selection
Figure 8. VBAT = 3.8 V: VOUT = 2.0 V: GPIO PFM mode selection
VBAT = 3.8 V: VOUT = 2.0 V: GPIO PFM mode selection
Figure 9. VBAT = 3.8 V: VOUT = 2.0 V: Auto mode extreme load transient
VBAT = 3.8 V: VOUT = 2.0 V: Auto mode extreme load transient
Figure 10. VBAT = 3.8 V: VOUT = 2.0 V: PWM mode extreme load transient
VBAT = 3.8 V: VOUT = 2.0 V: PWM mode extreme load transient
Figure 11. VBAT = 3.8 V: VOUT = 2.0 V: VBUS detach
VBAT = 3.8 V: VOUT = 2.0 V: VBUS detach
Figure 12. VOUT = 1.0 V: PWM Efficiency
VOUT = 1.0 V: PWM Efficiency
Figure 13. VOUT = 1.8 V: PWM efficiency
VOUT = 1.8 V: PWM Efficiency
Figure 14. VOUT = 2.1 V: PWM efficiency
VOUT = 2.1 V: PWM Efficiency
Figure 15. VOUT = 3.3 V: PWM efficiency
VOUT = 3.3 V: PWM Efficiency
Figure 16. VOUT = 1.0 V: Hysteretic efficiency
VOUT = 1.0 V: Hysteretic Efficiency
Figure 17. VOUT = 1.8 V: Hysteretic efficiency
VOUT = 1.8 V: Hysteretic Efficiency
Figure 18. VOUT = 2.1 V: Hysteretic efficiency
VOUT = 2.1 V: Hysteretic Efficiency
Figure 19. VOUT = 3.3 V: Hysteretic efficiency
VOUT = 3.3 V: Hysteretic Efficiency
Figure 20. VOUT = 1.8 V: FFT 10 mA: PFM
VOUT = 1.8 V: FFT 10 mA
Figure 21. VOUT = 1.8 V: FFT 50 mA: PFM
VOUT = 1.8 V: FFT 50 mA
Figure 22. VOUT = 1.8 V: FFT 100 mA: PWM: clock = 3.6 MHz
VOUT = 1.8 V: FFT 100 mA
Figure 23. VOUT = 1.8 V: FFT 200 mA: PWM: clock = 3.6 MHz
VOUT = 1.8 V: FFT 200 mA
Figure 24. BUCK dropout
BUCK Dropout

Registers

Instances

Instance Base address Description
BUCK 0x00000400

BUCK registers

BUCK register

Register overview

Register Offset Description
BUCK1ENASET 0x0

Enable BUCK1
BUCK1ENACLR 0x1

Disable BUCK1
BUCK2ENASET 0x2

Enable BUCK2
BUCK2ENACLR 0x3

Disable BUCK2
BUCK1PWMSET 0x4

Enable PWM mode for BUCK1
BUCK1PWMCLR 0x5

Disable PWM mode for BUCK1
BUCK2PWMSET 0x6

Enable PWM mode for BUCK2
BUCK2PWMCLR 0x7

Disable PWM mode for BUCK2
BUCK1NORMVOUT 0x8

Configure BUCK1 output voltage normal mode
BUCK1RETVOUT 0x9

Configure BUCK1 output voltage retention mode
BUCK2NORMVOUT 0xA

Configure BUCK2 output voltage normal mode
BUCK2RETVOUT 0xB

Configure BUCK2 output voltage retention mode
BUCKENCTRL 0xC

Select GPIOs for BUCK1 and BUCK2 enabling
BUCKVRETCTRL 0xD

Select GPIOs for controlling BUCK1 and BUCK2 retention voltage selection
BUCKPWMCTRL 0xE

Select GPIOs for PWM mode controlling BUCK1 and BUCK2
BUCKSWCTRLSEL 0xF

BUCK output voltage set by pin or register
BUCK1VOUTSTATUS 0x10

BUCK1 output voltage target
BUCK2VOUTSTATUS 0x11

BUCK2 output voltage target
BUCKCTRL0 0x15

BUCK auto mode and pull down control
BUCKSTATUS 0x34

BUCK status register

BUCK1ENASET

Address offset: 0x0

Enable BUCK1

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

TASKBUCK1ENASET

Enable BUCK1

NOEFFECT

0

No effect

SET

1

Enable

BUCK1ENACLR

Address offset: 0x1

Disable BUCK1

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

TASKBUCK1ENACLR

Disable BUCK1

NOEFFECT

0

No effect

SET

1

Disable

BUCK2ENASET

Address offset: 0x2

Enable BUCK2

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

TASKBUCK2ENASET

Enable BUCK2

NOEFFECT

0

No effect

SET

1

Enable

BUCK2ENACLR

Address offset: 0x3

Disable BUCK2

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

TASKBUCK2ENACLR

Disable BUCK2

NOEFFECT

0

No effect

SET

1

Disable

BUCK1PWMSET

Address offset: 0x4

Enable PWM mode for BUCK1

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

TASKBUCK1PWMSET

Enable PWM mode for BUCK1

NOEFFECT

0

No effect

SET

1

Enable

BUCK1PWMCLR

Address offset: 0x5

Disable PWM mode for BUCK1

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

TASKBUCK1PWMCLR

Disable PWM mode for BUCK1 and return to auto mode

NOEFFECT

0

No effect

SET

1

Disable

BUCK2PWMSET

Address offset: 0x6

Enable PWM mode for BUCK2

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

TASKBUCK2PWMSET

Enable PWM mode for BUCK2

NOEFFECT

0

No effect

SET

1

Enable

BUCK2PWMCLR

Address offset: 0x7

Disable PWM mode for BUCK2

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

TASKBUCK2PWMCLR

Disable PWM mode for BUCK2 and return to auto mode

NOEFFECT

0

No effect

SET

1

Disable

BUCK1NORMVOUT

Address offset: 0x8

Configure BUCK1 output voltage normal mode

Bit number 7 6 5 4 3 2 1 0
ID A A A A A
Reset 0x02 0 0 0 0 0 0 1 0
ID R/W Field Value ID Value Description
A

RW

BUCK1NORMVOUT

Configure BUCK1 output voltage normal mode

1V

0

1.0 V

1V1

1

1.1 V

1V2

2

1.2 V (default)

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

2V0

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

3V0

20

3.0 V

3V1

21

3.1 V

3V2

22

3.2 V

3V3

23

3.3 V

3V30

24

3.3 V

BUCK1RETVOUT

Address offset: 0x9

Configure BUCK1 output voltage retention mode

Bit number 7 6 5 4 3 2 1 0
ID A A A A A
Reset 0x02 0 0 0 0 0 0 1 0
ID R/W Field Value ID Value Description
A

RW

BUCK1RETVOUT

Configure BUCK1 output voltage retention mode

1V

0

1.0 V

1V1

1

1.1 V

1V2

2

1.2 V (default)

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

2V0

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

3V0

20

3.0 V

3V1

21

3.1 V

3V2

22

3.2 V

3V3

23

3.3 V

3V30

24

3.3 V

BUCK2NORMVOUT

Address offset: 0xA

Configure BUCK2 output voltage normal mode

Bit number 7 6 5 4 3 2 1 0
ID A A A A A
Reset 0x08 0 0 0 0 1 0 0 0
ID R/W Field Value ID Value Description
A

RW

BUCK2NORMVOUT

Configure BUCK2 output voltage normal mode

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 (default)

1V9

9

1.9 V

2V0

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

3V0

20

3.0 V

3V1

21

3.1 V

3V2

22

3.2 V

3V3

23

3.3 V

3V30

24

3.3 V

BUCK2RETVOUT

Address offset: 0xB

Configure BUCK2 output voltage retention mode

Bit number 7 6 5 4 3 2 1 0
ID A A A A A
Reset 0x08 0 0 0 0 1 0 0 0
ID R/W Field Value ID Value Description
A

RW

BUCK2RETVOUT

Configure BUCK2 output voltage retention mode

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 (default)

1V9

9

1.9 V

2V0

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

3V0

20

3.0 V

3V1

21

3.1 V

3V2

22

3.2 V

3V3

23

3.3 V

3V30

24

3.3 V

BUCKENCTRL

Address offset: 0xC

Select GPIOs for BUCK1 and BUCK2 enabling

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

RW

BUCK1ENGPISEL

Select which GPIO controls BUCK1 enable

NOTUSED

0

Not used

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

NOTUSED1

6

No GPIO selected

NOTUSED2

7

No GPIO selected
B

RW

BUCK2ENGPISEL

Select which GPIO controls BUCK2 enable

NOTUSED1

0

Not used

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

NOTUSED3

6

No GPIO selected

NOTUSED4

7

No GPIO selected
C

RW

BUCK1ENGPIINV

Invert the sense of the selected GPIO for BUCK1

NORMAL

0

Not inverted

INVERTED

1

Inverted
D

RW

BUCK2ENGPIINV

Invert the sense of the selected GPIO for BUCK2

NORMAL

0

Not inverted

INVERTED

1

Inverted

BUCKVRETCTRL

Address offset: 0xD

Select GPIOs for controlling BUCK1 and BUCK2 retention voltage selection

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

RW

BUCK1VRETGPISEL

Select which GPIO controls BUCK1 retention voltage

NOTUSED

0

Not used

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

Not used

NOTUSED1

7

Not used
B

RW

BUCK2VRETGPISEL

Select which GPIO controls BUCK2 retention voltage

NOTUSED

0

Not used

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

Not used

NOTUSED1

7

Not used
C

RW

BUCK1VRETGPIINV

Invert the sense of the selected GPIO for BUCK1

NORMAL

0

Not inverted

INVERTED

1

Inverted
D

RW

BUCK2VRETGPIINV

Invert the sense of the selected GPIO for BUCK2

NORMAL

0

Not inverted

INVERTED

1

Inverted

BUCKPWMCTRL

Address offset: 0xE

Select GPIOs for PWM mode controlling BUCK1 and BUCK2

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

RW

BUCK1PWMGPISEL

Select which GPIO controls BUCK1 force PWM

NOTUSED1

0

Not used

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

NOTUSED

6

Not used

NOTUSED2

7

Not used
B

RW

BUCK2PWMGPISEL

Select which GPIO controls BUCK2 force PWM

NOTUSED1

0

Not used

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

NOTUSED

6

Not used

NOTUSED2

7

Not used
C

RW

BUCK1PWMGPIINV

Invert the sense of the selected GPIO for BUCK1

NORMAL

0

Not inverted

INVERTED

1

Inverted
D

RW

BUCK2PWMGPIINV

Invert the sense of the selected GPIO for BUCK2

NORMAL

0

Not inverted

INVERTED

1

Inverted

BUCKSWCTRLSEL

Address offset: 0xF

BUCK output voltage set by pin or register

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

RW

BUCK1SWCTRLSEL

Output voltage control for BUCK1

VSETANDSWCTRL

0

VSET pin controls output voltage

SWCTRL

1

Register controls output voltage
B

RW

BUCK2SWCTRLSEL

Output voltage control for BUCK2

VSETANDSWCTRL

0

VSET pin controls output voltage

SWCTRL

1

Register controls output voltage

BUCK1VOUTSTATUS

Address offset: 0x10

BUCK1 output voltage target

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

R

BUCK1VOUTSTATUS

Selected VOUT target

BUCK2VOUTSTATUS

Address offset: 0x11

BUCK2 output voltage target

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

R

BUCK2VOUTSTATUS

Selected VOUT target

BUCKCTRL0

Address offset: 0x15

BUCK auto mode and pull down control

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

RW

BUCK1AUTOCTRLSEL

BUCK1 control

AUTO

0

Select auto switching between PFM and PWM

PFM

1

Select PFM mode only
B

RW

BUCK2AUTOCTRLSEL

BUCK2 control

AUTO

0

Select auto switching between PFM and PWM

PFM

1

Select PFM mode only
C

RW

BUCK1ENPULLDOWN

BUCK1 pull down

LOW

0

BUCK1 pull down disabled

HIGH

1

BUCK1 pull down enabled
D

RW

BUCK2ENPULLDOWN

BUCK2 pull down

LOW

0

BUCK2 pull down disabled

HIGH

1

BUCK2 pull down enabled

BUCKSTATUS

Address offset: 0x34

BUCK status register

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

R

BUCK1MODE

BUCK1 mode

AUTOMODE

0

Auto mode

PFMMODE

1

PFM mode

PWMMODE

2

Force PWM mode

RFU

3

Reserved (PWM mode)
B

R

BUCK1PWRGOOD

BUCK1 status

BUCKDISABLED

0

BUCK powered off

BUCKPOWERED

1

BUCK powered on
C

R

BUCK1PWMOK

BUCK1 PWM status

PWMMODEDISABLED

0

PWM mode disabled

PWMMODEENABLED

1

PWM mode enabled
D

R

BUCK2MODE

BUCK2 mode

AUTOMODE

0

Auto mode

PFMMODE

1

PFM mode

PWMMODE

2

Force PWM mode

RFU

3

Reserved (PWM mode)
E

R

BUCK2PWRGOOD

BUCK2 status

BUCKDISABLED

0

BUCK powered off

BUCKPOWERED

1

BUCK powered on
F

R

BUCK2PWMOK

BUCK2 PWM status

PWMMODEDISABLED

0

PWM mode disabled

PWMMODEENABLED

1

PWM mode enabled