IMP522

IMP522

© 2001 IMP, Inc.

Electroluminescent Lamp Drivers

5

Power Sequencing

voltage and when it exceeds the threshold range (0.2V to 0.9V) it

powers up the oscillator and internal bias modules. This starts a

delay counter which is one half of the EL oscillator period, after

which power to the high voltage internal modules is applied. The

IMP522 is then operating fully.

logic gate. When the voltage on the driver side of the resistor falls

pin. This immediately powers down the internal high-voltage

circuits, which effectively shuts the lamp off. At this point the

oscillator and bias modules still draw quiescent current, but oscil-

oscillator and bias modules are also fully powered down.

Figure 1. Driver Waveforms

522_03.eps

IN (Pulse)

Power Saving Disable Mode

When disabled, the IMP522 quiescent current drops to typically 20nA.

In die form, an extra pin ENABLE is available (contact factory).

can be driven by a microcontroller.

Oscillator Frequency Adjustment

The EL lamp drive and PWM boost converter oscillation frequen-

cies can be programmed independently.

determines the Inductor Switching (or PWM-) frequency. For the

recommended nominal resistor value of 910k

Ω, the frequency is

61kHz. For other resistor values, the frequency is inversely pro-

portional to the resistor value. Increasing the resistance will lower

the frequency.

determines the EL lamp drive frequency. For the recommended

nominal resistor value of 2.7M

Ω, the frequency is 250Hz. For

other resistor values, the frequency is inversely proportional to

the resistor value: increasing the resistance will lower the fre-

quency.

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Application Information