XC9206 / 9207/ 9208 Series

PWM, PWM/PFM Switchable Step-Down DC/DC Converters with Driver Transistor Built-In

< U.V.L.O. Circuit>

< Function of CE/MODE pin >

(A)

(B)

(A)

(B)

(A)

(B)

(A)

(B)

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 >

When the VIN pin voltage becomes 1.4 V or lower, the P-channel output driver transistor is forced OFF to prevent false pulse output caused by unstable

operation of the internal circuitry. When the VIN pin voltage becomes 1.8 V or higher, switching 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.

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 VOUT pin. 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.).

Chip Disable

PWM control (XC9206), PWM/PFM automatic switching control (XC9207)

SW_CE

ON

OFF

STATUS

SW_CE

STATUS

ON

PWM control (XC9206), PWM/PFM automatic switching control (XC9207)

*

ON

Synchronous PWM control

OFF

Chip Disable

SW_CE

ON

STATUS

OFF

OFF

Synchronous PWM control

Chip Disable

ON

*

OFF

ON

Non-synchronous PWM/PFM automatic switching control

SW_CE SW_PMW/PFM

STATUS

OFF

OFF

Non-synchronous PWM/PFM automatic switching control

Chip Disable

OFF

SW_PMW/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.

Semiconductor Ltd.

CE/ MODE

VIN

VDD

R1

SW_CE

CE/ MODE

VIN

VDD

R2

SW_CE

CE/MODE

VIN

VDD

RM1

SW _ PW M/ PFM

RM2

SW_CE

CE/ MODE

VIN

VDD

RM1

SW_ PWM/PFM

RM2

SW_CE

Data Sheet

11