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PDF HV857L Data sheet ( Hoja de datos )
| Número de pieza | HV857L | |
| Descripción | High Voltage EL Lamp Driver IC | |
| Fabricantes | Supertex | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de HV857L (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
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Supertex inc.
HV857L
Low Noise, High Voltage
EL Lamp Driver IC
Features
►►Audible noise reduction
►►190 VPP output voltage for higher brightness
►►Single cell lithium ion compatible
►►150nA shutdown current
►►Wide input voltage range 1.8V to 5.0V
►►Separately adjustable lamp and converter
frequencies
►►Output voltage regulation
►►Split supply capability
►►Available in 8-Lead DFN and 8-Lead MSOP-
packages
Applications
►► Mobile cellular phones
►► Keypad backlighting
►► LCD backlighting
►► PDAs
►► Handheld wireless communication products
►► Global Positioning Systems (GPS)
General Description
The Supertex HV857L is a low noise, high voltage driver designed
for driving Electroluminescent (EL) lamps of up to five square
inches. It is the low noise version of the EL lamp driver HV857. The
input supply voltage range is from 1.8V to 5.0V. The device uses
a single inductor and a minimum number of passive components.
The nominal regulated output voltage that is applied to the EL
lamp is ±95V. The chip can be enabled/disabled by connecting the
resistor on RSW-Osc to VDD/ground.
The HV857L has two internal oscillators, a switching MOSFET,
and a high voltage EL lamp driver. The frequency for the switching
MOSFET is set by an external resistor connected between the RSW-
Osc pin and the supply pin, VDD. The EL lamp driver frequency
is set by an external resistor connected between the REL-Osc
and VDD pins. An external inductor is connected between the LX
and VDD pins, or VIN for split supply applications. A 0.003-0.1µF
capacitor is connected between CS and ground. The EL lamp is
connected between the VA and VB pins.
The switching MOSFET charges the external inductor and
discharges it into the capacitor at CS. The voltage at CS will start
to increase. Once the voltage at CS reaches a nominal value of
95V, the switching MOSFET is turned OFF to conserve power.
The outputs VA and VB are configured as an H bridge, and are
switching in opposite states to achieve ±95V across the EL lamp.
Typical Application Circuit
ON = VDD
OFF = 0
V+_DD
+
_VIN
Enable Signal
1 VDD
VA 8
CDD
RSW
HV857L
2 RSW-Osc
VB 7
3 REL-Osc
CIN REL 4 GND
CS 6
LX 5
EL Lamp
D
LX CS
Doc.# DSFP-HV857L
A062013
Supertex inc.
www.supertex.com
1 page  
Typical Waveform on VA, VB and Differential Waveform VA - VB
HV857L
Fig. 2: Split Supply and Enable/Disable Configuration
ON = VDD
OFF = 0V
Regulated Voltage = VDD
Battery Voltage = VIN
Enable Signal
CDD
RSW
REL
CIN
18
VDD
VA
2 HV857L 7
RSW-Osc
VB
3
REL-Osc
6
CS
4
GND
5
LX
D
LX
EL Lamp
CS
Split Supply Configuration
The HV857L can also be used for handheld devices operat-
ing from a battery where a regulated voltage is available.
This is shown in Fig. 2. The regulated voltage can be used
to run the internal logic of the HV857L. The amount of cur-
rent necessary to run the internal logic is 150µA maximum at
a VDD of 5.0V. Therefore, the regulated voltage could easily
provide the current without being loaded down.
Enable/Disable Configuration
The HV857L can be easily enabled and disabled via a logic
control signal on the RSW and REL resistors as shown in Fig.
2 below. The control signal, which can be from a micropro-
cessor, has to track the VDD supply. RSW and REL are typi-
cally very high values. Therefore, only 10’s of microamperes
will be drawn from the logic signal when it is at a logic high
(enable) state. When the microprocessor signal is high, the
device is enabled, and when the signal is low, it is disabled.
Audible Noise Reduction
The EL lamp, when lit, emits an audible noise. This is due to
EL lamp construction and it creates a major problem for ap-
plications where the EL lamp can be close to the ear such as
cellular phones. The HV857L employs a circuit designed to
help minimize the EL lamp’s audible noise by slowing down
the rise and fall times seen by the EL lamp.
Doc.# DSFP-HV857L
A062013
Supertex inc.
5 www.supertex.com
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet HV857L.PDF ] | |
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