NOTES ON USE

1. Checking for Intermittent Oscillation

2. PWM/PFM Automatic Switching

3. Ratings

Use the XC9210 series and peripheral components within the limits of their ratings.

4. Reverse Current

5. Switching Method of Operational Mode / Control

9

* The light load condition mentioned above means that the load current when the coil current being discontinuous at non-synchronous operation. The heavy

load condition means that the load current when the coil current being continuous at non-synchronous operation. The DC/DC simulation on the TOREX

website is useful to determine whether the coil current is non-synchronous or synchronous under your operating conditions. After the simulation, please test

with the actual device.

Non-Synchronous, PFM / PWM Automatic Switching Control

OPERATIONAL MODE / CONTROL

Synchronous, PWM Control

Non-Synchronous, PWM Control

Non-Synchronous, PFM / PWM Automatic Switching Control

'L'

'H'

'L'

'H'

'L'

MODE

'H'

'H'

'L'

PWM

XC9210 Series

Synchronous Step-Down DC / DC Controller ICs

The XC9210 series is subject to intermittent oscillation in the proximity of the maximum duty if the step-down ratio is low (e.g., from 4.2 V to 3.3 V) or a

heavy load is applied where the duty ratio becomes high. Check waveforms at EXT under your operating conditions. A remedy for this problem is to

raise the inductance of coil L or increase the load capacitance CL and use OS-CON for the load capacitance CL. When using OS-CON for the load

capacitance and setting output voltage low, the series could produce an abnormal oscillation. In such case, please test with the actual device.

If PWM/PFM automatic switching control is selected and the step-down ratio is high (e.g., from 10 V to 1.0 V), the control mode remains in PFM setting

over the whole load range, since the duty ratio under continuous-duty condition is smaller than the PFM duty ratio of the XC9210 series. The output

voltage's ripple voltage becomes substantially high under heavy load conditions, with the XC9210 series appearing to be producing an abnormal

oscillation. If this operation becomes a concern, set pins PWM1 and PWM2 to High to set the control mode to PWM setting. For use under the above-

mentioned condition, measured data of PWM/PFM automatic switching control shown on the data sheets are available up to IOUT = 100 mA.

Reverse current is produced under the

conditions of synchronous operation and light

load (current flows from the output to the input ).

If this reverse current becomes a concern,

operate under synchronous rectification during

heavy load conditions, or move input

capacitance CIN closer to the IC to reduce the

reverse current to the power supply.

0mA

ILmax

Coil Current WhenNon-Synchronous

(DiscontinuousMode)

IL

0mA

ILmax

ILmin

Coil Current WhenSynchronous

Reverse

Current

ILmax

ILmin

IL

Coil Current with no reverse current

Comparison among non-synchronous operation (left), synchronous operation (center) and the coil current on a like-for-like

basis. Synchronous of the current IL< 0mA becomes reverse current.

To prevent the reverse current, operate in the condition of ILmin > 0mA (right).

Lx

EX T 1

EX T 2

IC

VOUT

CIN

VIN

GND

Reverse Current

L

CL

Semiconductor Ltd.