IMP522 Ver la hoja de datos (PDF) - IMP, Inc
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IMP522 Datasheet PDF : 6 Pages
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IMP522
Application Information
EL Lamp Drive
The outputs VA – VAB and VB – VAB are configured as H-bridges,
driven by the EL oscillator. Each output is switched between CS
and ground on alternate phases, creating peak-to-peak signals
across the EL lamps of twice the regulated voltage.
EL Lamp Selection: LMPSEL
The digital input pin LMPSEL allows either or both EL lamps to
be active. Lamp A is active when LMPSEL is LOW and lamp B is
active when LMPSEL is HIGH. When LMPSEL is left floating or
driven by a three-state driver in the high impedance state, both
lamp driver outputs are active.
LMPSEL
Signal
HIGH
Lamp A Drive
VA and VAB
OFF
Lamp B Drive
VB and VAB
ON
LOW
ON
Floating/
High Impedance
ON
OFF
ON
522_t02.eps
The logic HIGH signal level is defined as greater than 0.7VDD and
logic LOW is defined as less than 0.3VDD. A floating level is rec-
ognized with the signal level between 0.3VDD and 0.7VDD, or
when the output impedance of the driving voltage signal source
is infinite (driver in OFF state).
EL Driver Output Overvoltage Regulator
The IMP522 maximum VCS output voltage is between 110V and
120V. The internal overvoltage regulator skips the inductor
switching whenever the voltage on the CS pin exceeds the regula-
tion threshold. The internal overvoltage detection trip point has a
hysterisis of 1V and a range of 110V to 120V at room temperature.
PWM Circuit Switching
The switching MOSFET is driven by the PWM signal (nominally
61kHz). During the first 88% of the period, the switch is ON,
providing a low impedance path (<8Ω) from LX to ground. This
causes the external inductor to charge. In the last 12% of the
period, the MOSFET is turned OFF. This causes the voltage on
the output of LX to rise up to a high value. At some point, this will
forward-bias the external diode, thus pumping charge into the
storage capacitor CS. The voltage on CS increases each cycle to
between 110V and 120V. When the internal regulation trip-point is
reached, the overvoltage regulator turns the MOSFET switch OFF
to conserve power.
Both drivers are OFF if the IMP522 is disabled.
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© 2001 IMP, Inc.
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