［AP2152］

MS1348-E-00

9

2012/05

2) Functions

2-1) PWM Input circuit

The AP2152 achieves PWM dimming by applying a PWM signal to the PWM pin. The PWM pin is also

used as the enable function of the IC.

At startup, if a high level PWM signal is applied to the PWM pin and maintained for more than 36us,

the standby mode will be released. If the high level of PWM signal within the range of

is applied longer than 7us to the PWM pin after releasing the standby

mode, the operation mode is maintained and direct PWM dimming by PWM signal is simultaneously

of the PWM dimming signal, and the current will be 0mA during a low level of the PWM dimming

signal.

If a low level PWM signal is maintained longer than 50ms after the LED is lit, the IC will be in the

standby mode.

2-2) 5V Regulator

The AP2152 has a built in low dropout linear regulator to supply voltage for the internal circuits. If a

low level is applied to the PWM pin, the VDC is approximately 0V, and if a high level is applied to the

PWM pin, the VDC outputs 5V. The VDC pin, the output of the LDO, outputs 5V while the supply voltage

ranges from 6V to 35V. If the supply voltage is less than 6V, the output voltage decreases depending on

the supply voltage. If the supply voltage goes below the UVLO voltage, the IC ceases operation. If the

supply voltage is between the UVLO voltage and 6V, the IC operates but the characteristics are not

guaranteed.

Please connect 1uF capacitor between the VDC pin and GND.

2-3) LED current setting

The AP2152 has 3 channel LED constant current circuits built in. By connecting 10 LEDs in series per

channel, a maximum of 30 LEDs can be driven. Maximum LED current per channel is 120mA. The LED

the ISET pin and GND. If the ISET pin is affected by noise, the LED current becomes unstable, so

should be placed as close to the IC as possible. The ISET pin sets the LED current for all channels.

(CH1~CH3)

ISET pin. Please check the LED current (thoroughly) when designing the actual board.

　

)

k

(

R

2730

=

)

mA

(

ILED

ISET

2-4) Switching frequency setting/Synchronize with external clock

The AP2152 can set the DC/DC boost converter switching frequency in the range from 0.2MHz to

The AP2152 switching frequency can be synchronized to an external clock signal. If an external

clock signal is applied to the SYNC pin, the switching frequency synchronizes to the external clock’s

rising edge. If a low level is applied to the SYNC pin for approximately 10us during the synchronization

operation, it becomes self-oscillating.

(If low level is applied to the SYNC pin in the synchronization operation for approximately 10us, it

becomes self-oscillation operation.)

Please check (thoroughly) when designing the actual board.

　

80

+

)

k

(

R

×

695

.

7

10

=

)

MHz

(

F

T

3

OSC