ZXSC410/ZXSC420/ZXSC440

Document number: DS33618 Rev. 5 - 2

7 of 17

www.diodes.com

March 2013

© Diodes Incorporated

ZXSC410/ZXSC420/ZXSC440

Output Power Calculation

By making the above assumptions for inductance and peak current the output power can be determined by:

where







t

t

t

t

I

I

OFF

ON

DIS

ON

PK

AV

x

2







and

V

I

t

IN

PK

ON

xL



and

V

V

I

t

IN

IN

PK

DIS

xL





and

and

η = efficiency i.e. 100% = 1

Operating frequency can be derived by:

t

t

OFF

ON

1

f





Output Adjustment

The ZXSC410/420/440 are adjustable output controllers allowing the end user the maximum flexibilty. They can be used both as switching

voltage regulators and as constant current regulators. A feedback voltage of 300mV provides a good compromise for both voltage and current

regulation.

For a constant output voltage operation a potential divider network is connected as follows:

GND

The output voltage is determined by the equation:











 



RB

RA

1

V

V

FB

OUT

The resistor values, RA and RB, should be maximised to improve efficiency and decrease battery drain. Optimisation can be achieved by

Note: For the reference designs, RA is assigned the label R2 and RB the label R3.

The ZXSC410/420/440 can also be used to generate a constant current between boosted output rail and the VFB pin by connecting a single

resistor between VFB and GND.