Supertex inc.
High Voltage EL Lamp Driver
for Low Noise Applications
Features
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Patented audible noise reduction
Patented lamp aging compensation
210 V
PP
output voltage for higher brightness
Patented output timing for high efficiency
Single cell lithium ion compatible
150nA shutdown current
Wide input voltage range 1.8 to 5.0V
Separately adjustable lamp and converter
frequencies
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Output voltage regulation
►
Split supply capability
HV859
General Description
The Supertex HV859 is a high voltage driver designed for driving
Electroluminescent (EL) lamps of up to 5.0 square inches. The
input supply voltage range is from 1.8 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 ±105V. The chip can be enabled/disabled by connecting
the resistor on RSW-Osc to VDD/ground.
The HV859 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 REL-Osc pin and the VDD pin. 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 VA and VB.
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 105V, 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 ±105V across
the EL lamp.
Applications
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LCD backlighting
Mobile Cellular Phone keypads
PDAs
Handheld wireless communication products
Global Positioning Systems (GPS)
Typical Application Circuit
ON = V
DD
OFF = 0V
V
DD
+
-
R
EL
C
IN
C
DD
R
SW
1 VDD
Enable
R
SER
HV859
VA 8
VB 7
CS 6
LX
5
EL Lamp
2 RSW-Osc
3 REL-Osc
D
C
S
+
V
IN
-
4 GND
L
X
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089
Tel: 408-222-8888
www.supertex.com
HV859
Ordering Information
Package Options
Device
HV859
3.00x3.00mm body
0.80mm height (max)
0.65mm pitch
Pin Configurations
3.00x3.00mm body
1.10mm height (max)
0.65mm pitch
8-Lead DFN
8-Lead MSOP
VDD
1
RSW-Osc
REL-Osc
2
3
8
7
VA
VB
6
CS
5
LX
HV859K7-G
HV859MG-G
GND
4
-G indicates package is RoHS compliant (‘Green’)
8-Lead DFN (K7)
(top view)
(Pads are on the bottom of the package)
VDD
1
RSW-Osc
REL-Osc
2
3
4
8
7
6
5
VA
VB
CS
LX
Absolute Maximum Ratings
Parameter
V
DD
, Supply voltage
Operating temperature
Storage temperature
Power dissipation: 8-Lead DFN (K7)
Power dissipation: 8-Lead MSOP (MG)
V
CS
, Output voltage
Value
-0.5V to 6.5V
-40°C to +85°C
-65°C to +150°C
1.6W
300mW
-0.5V to +130V
GND
8-Lead MSOP (MG)
(top view)
Product Marking
H859
YWLL
Y = Last Digit of Year Sealed
W = Code for Week Sealed
L = Lot Number
= “Green” Packaging
Absolute Maximum Ratings are those values beyond which damage to the device may
occur. Functional operation under these conditions is not implied. Continuous operation
of the device at the absolute rating level may affect device reliability. All voltages are
referenced to device ground.
Package may or may not include the following marks: Si or
8-Lead DFN (K7)
Top Marking
Thermal Resistance
Package
8-Lead DFN (K7)
8-Lead MSOP (MG)
θ
ja
60 °C/W
330 °C/W
H859
LLLL
Bottom Marking
YYWW
L = Lot Number
YY = Year Sealed
WW = Week Sealed
= “Green” Packaging
Package may or may not include the following marks: Si or
8-Lead MSOP (MG)
Recommended Operating Conditions
Sym
V
DD
f
EL
T
A
Parameter
Supply voltage
Output drive frequency
Operating temperature
Min
1.8
-
-40
Typ
-
-
-
Max
5.0
1.0
+85
Units
V
kHz
°C
Conditions
---
---
---
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089
2
Tel: 408-222-8888
www.supertex.com
HV859
Enable/Disable Function Table
Sym
EN-L
EN-H
Parameter
Logic input low voltage
Logic input high voltage
Min
0
V
DD
- 0.2
Typ
-
-
Max
0.2
V
DD
Units
V
V
Conditions
V
DD
= 1.8 to 5.0V
V
DD
= 1.8 to 5.0V
Electrical Characteristics
Sym
R
DS(ON)
V
CS
V
A
– V
B
I
DDQ
I
DD
I
IN
V
CS
F
EL
Fsw
D
Parameter
DC Characteristics
(Over recommended operating conditions unless otherwise specified V
IN
= V
DD
= 3.3V, T
A
= 25°C)
Min
-
95
190
-
-
-
-
175
-
-
Typ
-
105
210
-
-
26
90
205
77
88
Max
6.0
115
230
150
150
35
-
235
-
-
Units
Ω
V
V
nA
µA
mA
V
Hz
kHz
%
Conditions
I = 100mA
V
DD
= 1.8 to 5.0V
V
DD
= 1.8 to 5.0V
R
SW-Osc
= Low
V
DD
= 1.8 to 5.0V. See Fig. 1.
See Fig. 1.*
See Fig. 1.
See Fig. 1.
---
See Fig. 1.
On-resistance of switching transistor
Max. output regulation voltage
Peak to peak output voltage
Quiescent V
DD
supply current
Input current going into the VDD pin
Input current including inductor
current
Output voltage on VCS
EL lamp frequency
Switching transistor frequency
Switching transistor duty cycle
* The inductor used is a 220µH Murata inductor, max DC resistance of 8.4Ω, part # LQH32CN221K21.
Functional Block Diagram
VDD
LX
CS
Q
VA
RSW-Osc
Switch
OSC
V
SENSE
High
Voltage
Level
Trans-
lators
Disable
V
DD
RSW-Osc
Switch
OSC
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089
3
-
V
REF
C
+
GND
Q
Q
VB
Q
Tel: 408-222-8888
www.supertex.com
HV859
Fig. 1: Typical Application/Test Circuit
ON = V
DD
OFF = 0V
560k
V
DD
2.0M
1.0 F
Enable Signal
1 VDD
2.0k
HV859
VA 8
VB 7
CS 6
LX
5
Equivalent to 3.0in
2
lamp
10nF
2 RSW-Osc
3 REL-Osc
V
DD
= V
IN
+
-
BAS21**
220 H*
3.3nF
200V
4 GND
* Murata Inductor - LQH32CN221K21
** BAS21 - General Purpose HV diode
Fig. 2: Split Supply and Enable/Disable Configuration
ON = V
DD
OFF = 0V
R
SW
Regulated Voltage = V
DD
+
V
IN
-
Enable Signal
1 VDD
HV859
VA 8
VB 7
CS 6
LX
5
EL Lamp
2 RSW-Osc
3 REL-Osc
C
IN
R
EL
D
L
X
C
S
4 GND
Split Supply Configuration
The HV859 can also be used for handheld devices operating
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 HV859. The amount of current
necessary to run the internal logic is 150µA max at a V
DD
of
3.0V. Therefore, the regulated voltage could easily provide
the current without being loaded down.
The HV859 can be easily enabled and disabled via a logic
control signal on the R
SW
and R
EL
resistors as shown in Fig. 2
below. The control signal can be from a microprocessor. R
SW
and R
EL
are typically 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.
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089
4
Tel: 408-222-8888
www.supertex.com
HV859
Fig. 3: Typical Application Circuit for Audible Noise Reduction
ON = V
DD
OFF = 0V
+
V
DD
-
Enable
R
SER
C
DD
R
SW
1 VDD
VA 8
VB 7
CS 6
LX
5
HV859
EL Lamp
2 RSW-Osc
3 REL-Osc
R
EL
+
V
IN
-
C
IN
4 GND
D
C
S
L
X
Audible Noise Reduction
This section describes a method (patented) developed at
Supertex to reduce the audible noise emitted by the EL
lamps used in application sensitive to audible noise. Fig.
3 shows a general circuit schematic that uses the resistor,
R
SER
, connected in series with the EL lamp.
It is important to note that use of this resistor will reduce the
voltage across the lamp. Reduction of voltage across the
lamp will also have another effect on the over all performance
of the Supertex EL drivers, age compensation (patented).
This addresses a very important issue, EL lamp life that most
mobile phone manufacturers are concerned about.
As EL lamp ages, its brightness is reduced and its
capacitance is diminished. By using the RC model to reduce
the audible noise emitted by the EL lamp, the voltage across
the lamp will increase as its capacitance diminishes. Hence
the increase in voltage will compensate for the reduction of
the brightness. As a result, it will extend the EL lamp’s half-
life (half the original brightness).
How to Minimize EL Lamp Audible Noise:
The EL lamp, when lit, emits an audible noise. This is due
to EL lamp construction and it creates a major problem for
applications where the EL lamp can be close to the ear such
as cellular phones. The noisiest waveform is a square wave
and the quietest waveform has been assumed to be a sine
wave.
After extensive research, Supertex has developed a
waveform that is quieter than a sine wave. The waveform
takes the shape of approximately 2RC time constants for
rising and 2RC time constants for falling, where C is the
capacitance of the EL lamp, and R is the external resistor,
R
SER
, connected in series with the EL lamp. This waveform
has been proven to generate less noise than a sine wave.
The audible noise from the EL lamp can be set at a desired
level based on the series resistor value used with the lamp.
Effect of Series Resistor on EL Lamp Audible
Noise and Brightness:
Increasing the value of the series resistor with the lamp will
reduce the EL lamp audible noise as well as its brightness.
This is due to the fact that the output voltage across the lamp
will be reduced and the output waveform will have rounder
edges.
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089
5
Tel: 408-222-8888
www.supertex.com
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