[AP3603]

015000004-E-02

2015/07

- 11 -

12.1

Output Voltage Setting

Output voltage is settled by feedback resistors that are connected between the output capacitor and the GND.

The value of R3, R4 (output capacitor-FB pin) and R5, R6(FB pin-GND1) is calculated by the next

equations.





]

V

[

R4

R3

1

6

.

3

Vout

CH1

　　

＝









]

V

[

R6

R5

1

6

.

3

Vout

CH2

　　

＝





12.2

Operational Frequency Setting

Operational frequency is settled by the resistor R7 between the RT pin and the GND. The value of the

resistor is calculated by the next equations.

12.3

Maximum ON Duty Setting

Maximum On duty is settled by the resistor between MDC pin and GND. The value of the resistor is

calculated by the next equations.

Duty(typ) [%]

10k

60%

27k

70%

47k

80%

82k

90%

127k or more

(Note 6)

Note 6. Maximum ON duty is fixed by the operational frequency and minimum off time 250ns (typ). If

f>250kHz, duty may be limited by the minimum off time of the IC.

]

[

100

Frequency)

250ns

1

(

Duty

Max

％

　　

　

＝







12.4

Maximum Output Voltage

The maximum output voltage depends on maximum ON duty. It is estimated by the next equation.

[V]

Duty

1

.

1

Vin

Vout

Max

　　

＝



]

[

4

1.5V

3.2pF

1.2V

Hz

Frequency

5

.

0

R7

Ω

　　

　

＝





