KTB8331

December 2021

– Revision 04b

Page 12 of 25

Kinetic Confidential

After the correct range is selected, the KTB8331 register map contains two voltage setting registers to facilitate

hardware control of DVS using the VSEL pin. The first output voltage setting is I2C programmable using the

VOUT_VSEL0[6:0] bits (B6:0) in the VSEL0 configuration register (0x00). The second output voltage setting is

I2C programmable using the VOUT_VSEL1[6:0] bits (B6:0) in the VSEL1 configuration register (0x01). The output

voltage setting is given by:

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where G = 1.0 when the RANGE bit is 0, and G = 2.4 when the RANGE bit is 1. VOUT_VSELn is the decimal

equivalent of the binary bits of VOUT_VSEL0[6:0] or VOUT_VSEL1[6:0]. The default voltage settings are factory

trimmed, and several versions are available

– see the Ordering Information section.

Dynamic Voltage Scaling (DVS)

Dynamic Voltage Scaling (DVS) is used to slew the output voltage between two voltage settings contained in the

VSEL0 and VSEL1 registers

– see Setting the Output Voltage section. The VSEL pin selects which register is

used. Or, as an alternative method, I2C commands can be used by simply connecting the VSEL pin to ground

and dynamically writing a new setting into the VSEL0 register.

In either method, all DVS output voltage transitions are slew-rate-controlled by an on-chip up/down counter and

DAC. The DVS slew rate is I2C programmable using the SLEW[2:0] bits (B6:4) in the CONTROL configuration

register (0x02). DVS slewing is only possible within a single output voltage range; slewing between a voltage in

the low range and a voltage in the high range is not possible.

Forced-PWM vs. Auto-Skip Modes

The KTB8331 has two ways to control light-load switching behavior

– Forced-PWM mode and Auto-Skip mode.

In Forced-PWM, the switching frequency remains nearly constant. This mode is helpful for applications that are

noise sensitive.

In Auto-Skip mode, the KTB8331 transitions automatically between PWM switching at heavy loads and Skip/PFM

switching at light loads. Auto-Skip mode is helpful for applications that need high efficiency at light loads. While

skipping, single pulses are evenly spaced, resulting in the lowest output ripple and noise when compared to

compe

ting “pulse-grouping” or “burst mode” devices. Furthermore, the PFM frequency during single-pulse

skipping remains above the audio frequency band (20Hz to 20kHz) down to very light loads

– see the Typical

Operating Characteristics section.

The switching mode is I2C programmable using the MODE[1:0] bits (B1:0) in the CONTROL configuration register

(0x02). The MODE[1:0] bits work together with the VSEL pin to independently set the switching mode for the

VOUT_VSEL0[6:0] and VOUT_VSEL1[6:0] output voltage settings. The default mode settings are factory

trimmed, and several versions are available

– see the Ordering Information section.

Active Discharge

When the KTB8331 buck is disabled, an active discharge feature connects an on-chip resistor (RLX_DIS) between

the LX and PGND pins. This resistor discharges the output capacitor through the inductor. By default, this

feature is enabled; however, it can be disabled for applications that require a high impedance at the output during

shutdown. Enable and disable the active discharge feature via I2C commands by writing the DIS bit (B7) in the

CONTROL configuration register (0x02).

POR and Software Register Reset

The KTB8331 does NOT contain non-volatile memory for the register settings. When VIN rises above VPOR=1.8V,

either at initial power up or after a temporary VIN droop below VPOR, a Power-On Reset (POR) circuit resets all

registers to their factory default settings. Thereafter, as long as VIN remains above VPOR, the I2C registers

contents are retained, regardless if the buck is enabled or disabled. However, to reliably read or write to the I2C

registers, VIN should be above VUVLO.

To reset the registers manually via software, use I2C to write a 1 to the RESET bit (B2) in the CONTROL

configuration register (0x02). This resets nearly all registers to their default settings. There are a few exceptions,

as makes logical sense; refer to the CONTROL register description.