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■OPERATIONAL EXPLANATION (Continued)

●XC9206A / 07A series - Examples of how to use CE/MODE pin

●XC9208A series - Examples of how to use CE/MODE pin

Intermediate voltage can be generated by RM1 and RM2.

Please set the value of each R1, R2, RM1, RM2 at around 100k

Ω.

For switches, CPU open-drain I/O port and transistor can be used.

< PWM / PFM >

XC9207/9208 series features PWM/PFM automatic switching control.

With the automatic PWM/PFM switching control function, the series ICs are automatically switched from PWM control to

PFM control mode under light load conditions.

If during light load conditions the coil current becomes discontinuous and

on-time rate falls lower than PFM duty, the PFM circuit operates to output a pulse with a fixed on-time rate from the Lx pin.

During PFM operation with this fixed on-time rate, pulses are generated at different frequencies according to conditions of

the moment.

This causes a reduction in the number of switching operations per unit of time, resulting in efficiency

improvement under light load conditions.

However, since pulse output frequency is not constant, consideration should be

given if a noise filter or the like is needed.

Necessary conditions for switching to PFM operation depend on input voltage,

load current, coil value and other factors.

(A)

(B)

(A)

(B)

< U.V.L.O. Circuit>

output caused by unstable operation of the internal circuitry.

operation takes place.

By releasing the U.V.L.O. function, the IC performs the soft start function to initiate output startup

operation.

The soft start function operates even when the VIN pin voltage falls momentarily below the U.V.L.O. operating

voltage.

The U.V.L.O. circuit does not cause a complete shutdown of the IC, but causes pulse output to be suspended;

therefore, the internal circuitry remains in operation.

< Function of CE/MODE pin >

The XC9206/9207/9208 series will enter into shut down state by inputting a low level signal to the CE/MODE pin.

During a

shut down state, the current consumption of the IC becomes 0

μA (TYP.), with a state of high impedance at the Lx pin and

The IC starts its operation by inputting a high level signal to the CE/MODE pin.

The input of the CE/MODE pin is

a CMOS input and the sink current is 0

μA (TYP.).

SW_CE

STATUS

ON

Chip Disable

A

OFF

PWM control (XC9206),

PWM/PFM automatic switching control (XC9207)

ON

PWM control (XC9206),

PWM/PFM automatic switching control (XC9207)

B

OFF

Chip Disable

SW_CE

SW_PMW/PFM

STATUS

ON

*

Synchronous PWM control

OFF

ON

Non-synchronous PWM/PFM

automatic switching control

A

OFF

OFF

Chip Disable

ON

*

Chip Disable

OFF

ON

Non-synchronous PWM/PFM

automatic switching control

B

OFF

OFF

Synchronous PWM control