DIO6905C

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© 2023 DIOO MICROCIRCUITS CO., LTD

DIO6905C • Rev. 1.1

- 9 -

Detailed Description

The DIO6905C uses constant on-time control with input voltage feed-forward to stabilize the switching frequency

over its full input voltage range. It achieves 2 A of output current from a 2.3 V to 5.5 V input voltage range with

excellent load and line regulation. The output voltage can be regulated as low as 0.6 V.

Constant-on-time control

When compared to fixed-frequency PWM control, COT control offers a simpler control loop and faster transient

response. By using input voltage feed-forward, the DIO6905C maintains a nearly constant switching frequency

across the input and output voltage ranges. The switching pulse on time can be estimated with Equation (1):

t

*0.606us

OUT

ON

IN

V

V



(1)

To prevent inductor current runaway during the load transient, the DIO6905C has a fixed minimum off time of

60 ns.

Enable (EN)

When the input voltage is greater than the under-voltage lockout (UVLO) threshold (typically 2.1 V), the

DIO6905C can be enabled by pulling EN higher than 1.2 V. Leaving EN floating or pulling it down to ground

disables the DIO6905C. There is an internal 1 MΩ resistor from EN to ground.

When the DIO6905C is disabled, the part goes into output discharge mode automatically. The internal discharge

MOSFET provides a resistive discharge path for the output capacitor.

Soft-start

The DIO6905C has a built-in soft-start that ramps up the output voltage at a constant slew rate that avoids

overshooting at startup. The soft- start time is typically about 0.6 ms.

Current limit

The DIO6905C has the 2.4 A current limit for the HS-FET. When the HS-FET hits its current limit, the DIO6905C

enters current limit mode until the current drops to prevent the inductor current from rising and possibly damaging

the components.

Short circuit protection and recovery

The DIO6905C enters short-circuit protection (SCP) mode when it reaches the current limit and attempts to

recover from the short circuit by entering hiccup mode. In SCP, the DIO6905C disables the output power stage,

discharges the soft-start capacitor, and then enacts a soft-start procedure. If the short-circuit condition still holds

after the soft start ends, the DIO6905C repeats this cycle until the short circuit disappears and the output rises

back to regulation levels.