AT1450 查看數據表（PDF） - Unspecified

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AT1450

Photoflash Capacitor Charger for DSC

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AT1450

Preliminary Product Information

Photoflash Capacitor Charger for DSC

Functional Description

Soft Start

At power-on, the AT1450 enters the soft-start mode to prevent current spike and overshoot. The

capacitor CS is charged from 0.2V at a constant current of 1µA.

The soft-start time for the duty cycle

tS (s) = 0.8 × CS(µF )

Setting Oscillating Frequency

The oscillator circuit generates a triangular sawtooth wave with a peak of 0.8V and a trough of 0.1V

using the timing capacitor (CT) and the timing resistor (RT) that are connected to the OSC pin. This

oscillator can provide oscillating frequency in the range from 20KHz to 1MHz. The waveform of the

OSC pin is shown as Figure 2.

Figure 2 Oscillator Waveform

The cycle (T) can be determined as follows:

−t

VX = VHe CT×RT

t

=

−CT

×

RT

×

loge

(VX

VH

)

T = −CT × RT × loge (0.1/ 0.8) = 2.1× CT × RT [s]

Switching Regulator Function

(1) Reference voltage circuit

A temperature-compensated reference voltage (~1.25V) is generated by the reference voltage

circuit from the voltage supplied by the power supply pin (pin 3). The circuit also sets the idle

period besides providing the reference voltage for the switching regulator.

2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.

Tel: 886-3-563-0878

WWW: http://www.aimtron.com.tw

Fax: 886-3-563-0879

Email: service@aimtron.com.tw

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