MIC4834 Datasheet, PDF (5/12 Pages) Micrel Semiconductor – Low Noise Dual 220 VPP EL Driver

Micrel
Functional Diagram
MIC4834
Figure 1. MIC4834 Block Diagram
Functional Description
Overview
The MIC4834 is a high-voltage dual output EL driver with
a peak-to-peak AC output voltage of 220V capable of
driving two 3 in² EL panels. The MIC4834 drives EL
panels by converting a low DC input voltage to a high
DC high output voltage using the boost regulator circuit
and then alternating the high DC voltage across the EL
panel using an H-Bridge. Input supply current for the
MIC4834 is typically 152µA. The high voltage EL driver
has two internal oscillators to control the boost switching
frequency and the H-bridge driver frequency. The
internal boost oscillator frequency can be individually
programmed through an external resistor to maximize
efficiency and brightness of the EL panel. The H-bridge
frequency is internally fixed at 225Hz to reduce external
component count.
Regulation
Referring to Figure 1, power is initially applied to V_DD.
When the internal feedback voltage is less than the
reference voltage, the internal comparator enables
switching in the boost circuit. When the boost regulator
is switching, current flows through the inductor into the
switch. The switching MOSFET will typically turn on for
90% of the switching period. During the on-time, energy
October 2008
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M9999-100908-A