Supertex inc.
HV857
Low Noise, High Voltage
EL Lamp Driver IC
Features
General Description
►► Patented audible noise reduction
►► Patented lamp aging compensation
►► 190 VPP 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
►► Output voltage regulation
►► Split supply capability
►► Available in 8-Lead MSOP and DFN packages
The Supertex HV857 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 ±95V. The chip can be enabled/disabled by connecting the
resistor on RSW-Osc to VDD/GND.
The HV857 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 RELOsc pin and VDD pin. An external inductor is connected between
the LX and VDD pins or VIN for split supply applications. A 0.0030.1µF capacitor is connected between CS and ground. The EL
lamp is connected between VA and VB.
Applications
►►
►►
►►
►►
►►
LCD backlighting
Mobile Cellular Phone
PDAs
Handheld wireless communication products
Global Positioning Systems (GPS)
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
VDD
+
_
ON = VDD
OFF = 0
Enable Signal
1
CDD
RSW
2
3
VIN
+
_
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A062013
REL
CIN
4
VDD
HV857
VA
RSW-Osc
VB
REL-Osc
CS
GND
LX
8
EL Lamp
7
6
5
D
LX
CS
Supertex inc.
www.supertex.com
HV857
Pin Configuration
Ordering Information
Part Number
Package
Packing
HV857K7-G
8-Lead DFN
HV857MG-G
8-Lead MSOP
VDD
1
8
VA
RSW-Osc
2
7
VB
CS
REL-Osc
3
6
CS
LX
GND
4
5
LX
VDD
1
8
VA
3000/Reel
RSW-Osc
2
7
VB
2500/Reel
REL-Osc
3
6
GND
4
5
-G denotes a lead (Pb)-free / RoHS compliant package
Pads are at the bottom of the package.
Exposed center pad is at ground potential.
Value
-0.5V to 6.5V
Supply voltage, VDD
Product Marking
-40°C to +85°C
Storage temperature
-65°C to +150°C
DFN-8 power dissipation
MSOP-8 power dissipation
300mW
-0.5 to +120V
Output voltage, VCS
Package may or may not include the following marks: Si or
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.
8-Lead DFN
Top Marking
H857
LLLL
Typical Thermal Resistance
θja
8-Lead DFN
37OC/W
8-Lead MSOP
171OC/W
Y = Last Digit of Year Sealed
W = Code for Week Sealed
L = Lot Number
= “Green” Packaging
H857
YWLL
1.6W
Package
(top view)
(top view)
Parameter
Operating temperature
8-Lead MSOP
8-Lead DFN
Absolute Maximum Ratings
L = Lot Number
YY = Year Sealed
WW = Week Sealed
= “Green” Packaging
Bottom Marking
YYWW
Mounted on FR4 board, 25mm x 25mm x 1.57mm
Package may or may not include the following marks: Si or
8-Lead MSOP
Recommended Operating Conditions
Sym
Parameter
Min
Typ
Max
Units
VDD
Supply voltage
1.8
-
5.0
V
---
fEL
Operating drive frequency
-
-
1.0
kHz
---
TA
Operating temperature
-40
-
+85
C
---
O
Conditions
Enable/Disable Function Table
Sym
Parameter
Min
Typ
Max
Units
EN-L
EN-H
Conditions
Logic input low voltage
0
-
0.2
V
VDD = 1.8 to 5.0V
Logic input high voltage
VDD - 0.2
-
VDD
V
VDD = 1.8 to 5.0V
DC Electrical Characteristics (Over recommended operating conditions unless otherwise specified, T = 25°C)
A
Sym
RDS(ON)
VCS
Doc.# DSFP-HV857
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Parameter
On-resistance of switching transistor
Max. output regulation voltage
Min
Typ
Max
Units
-
-
6.0
Ω
I = 100mA
85
95
105
V
VDD=1.8 to 5.0V
2
Conditions
Supertex inc.
www.supertex.com
HV857
DC Electrical Characteristics (cont.)
Sym
Parameter
Min
Typ
Max
Units
Conditions
VA – VB
Peak to Peak output voltage
170
190
210
V
VDD=1.8 to 5.0V
IDDQ
Quiescent VDD supply current
-
-
150
nA
RSW-Osc = Low
IDD
Input current going into the VDD pin
-
-
150
µA
VDD= 1.8 to 5.0V. See Figure 1
IIN
Input current including inductor current
-
20
25
mA
See Figure 1*
VCS
Output voltage on VCS
-
84
-
V
See Figure 1
fEL
EL lamp frequency
205
240
275
Hz
See Figure 1
fSW
Switching transistor frequency
-
80
-
kHz
See Figure 1
D
Switching transistor duty cycle
-
88
-
%
See Figure 1
* The inductor used is a 220µH Murata inductor, max DC resistance of 8.4Ω, part # LQH32CN221K21.
Block Diagram
VDD
RSW-Osc
LX
CS
Switch
Osc
Q
GND
Disable
C
Q
VREF
_
High
Voltage
Level
Translator
VDD
Q
EL
Osc
REL-Osc
VA
VSENSE
+
VB
Q
Figure 1: Typical Application/ Test Circuit
ON = VDD
Enable Signal
OFF = 0V
+
1
0.1µF
560kΩ
VDD
3
-
+
2
2.0MΩ
4.7µF
4
VDD
HV857
VA
RSW-Osc
VB
REL-Osc
CS
GND
LX
8
2.0kΩ
Equivalent to 3.0in2 lamp
10nF
7
6
5
HV857
BAS21
220µH*
3.3nF
100V
VIN
-
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A062013
* Murata Inductor LQH32CN221K21
3
Supertex inc.
www.supertex.com
HV857
Typical Performance
Device
Lamp Size
VDD = VIN
IIN
VCS
fEL
Brightness
HV857MG-G
3.0in
3.3V
20.0mA
84V
240Hz
6.0ft-lm
2
Typical Performance Curves for Figure 1 (EL Lamp = 3.0in , V
2
VCS vs VIN
95
= 3.0V)
IIN vs VIN
25
23
lIN (mA)
85
VCS (V)
DD
75
65
21
19
17
15
55
1.5
2.5
3.5
4.5
13
1.5
5.5
2.5
Brightness vs VIN
7
3.5
4.5
5.5
85
95
VIN (V)
IIN vs VCS
24
6
22
5
lIN (mA)
Brightness (ft-lm)
VIN (V)
4
3
20
18
16
2
1
1.5
2.5
3.5
4.5
14
55
5.5
65
VIN (V)
75
VCS (V)
IIN, VCS, Brightness vs Inductor Value
100
7
90
6
VCS
80
lIN (mA), VCS (V)
Brightness
60
4
50
3
40
30
Brightness (ft-Im)
5
70
2
20
lIN
10
0
100
200
300
1
400
500
600
0
Inductor Value (µH)
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Supertex inc.
www.supertex.com
HV857
External Component Description
External
Component
Diode
CS Capacitor
Description
Fast reverse recovery diode, BAS21 diode or equivalent.
0.003µF to 0.1µF, 100V capacitor to GND is used to store the energy transferred from the inductor.
The EL lamp frequency is controlled via an external REL resistor connected between REL-Osc and VDD
of the device. The lamp frequency increases as REL decreases. As the EL lamp frequency increases,
the amount of current drawn from the battery will increase and the output voltage VCS will decrease. The
color of the EL lamp is dependent upon its frequency.
REL Resistor
RSW Resistor
LX Inductor
A 2MΩ resistor would provide lamp frequency of 205 to 275Hz. Decreasing the REL resistor by a factor
of 2 will increase the lamp frequency by a factor of 2.
(2MΩ)(240Hz)
fEL =
REL
The switching frequency of the converter is controlled via an external resistor, RSW between RSW-Osc
and VDD of the device. The switching frequency increases as RSW decreases. With a given inductor, as
the switching frequency increases, the amount of current drawn from the battery will decrease and the
output voltage, VCS, will also decrease.
(560kΩ)(80Hz)
fSW =
RSW
The inductor LX is used to boost the low input voltage by inductive flyback. When the internal switch is
on, the inductor is being charged. When the internal switch is off, the charge stored in the inductor will
be transferred to the high voltage capacitor CS. The energy stored in the capacitor is connected to the
internal H-bridge, and therefore to the EL lamp. In general, smaller value inductors, which can handle
more current, are more suitable to drive larger size lamps. As the inductor value decreases, the switching frequency of the inductor (controlled by RSW) should be increased to avoid saturation.
A 220µH Murata (LQH32CN221) inductor with 8.4Ω series DC resistance is typically recommended. For
inductors with the same inductance value, but with lower series DC resistance, lower RSW resistor value
is needed to prevent high current draw and inductor saturation.
Lamp
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As the EL lamp size increases, more current will be drawn from the battery to maintain high voltage
across the EL lamp. The input power, (VIN x IIN), will also increase. If the input power is greater than
the power dissipation of the package, an external resistor in series with one side of the lamp is recommended to help reduce the package power dissipation.
5
Supertex inc.
www.supertex.com
HV857
Split Supply Configuration
Enable/Disable Configuration
The HV857 can also be used for handheld devices operating
from a battery where a regulated voltage is available. This
is shown in Figure 2. The regulated voltage can be used to
run the internal logic of the HV857. The amount of current
necessary to run the internal logic is 150µA Max at a VDD of
3.0V. Therefore, the regulated voltage could easily provide
the current without being loaded down.
The HV857 can be easily enabled and disabled via a logic
control signal on the RSW and REL resistors as shown in Figure 2 below. The control signal can be from a microprocessor. The control signal has to track the VDD supply. RSW and
REL 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.
Figure 2: Split Supply and Enable/Disable Configuration
ON = VDD
Enable Signal
OFF = 0V
Regulated Voltage = VDD
1
RSW
CDD
2
3
REL
4
VDD
VA
RSW-Osc
VB
REL-Osc
CS
GND
LX
HV857
8
EL Lamp
7
6
D
5
+
VIN
-
CS
LX
CIN
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. Figure
3 shows a general circuit schematic that uses the resistor,
RSER, connected in series with the EL lamp.
Figure 3: Typical Application Circuit for Audible Noise Reduction
Enable
ON = VDD
OFF = 0V
VDD
1
+
RSW
CDD
-
3
REL
VIN
Doc.# DSFP-HV857
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2
4
+
-
VDD
HV857
VA
RSW-Osc
VB
REL-Osc
CS
GND
LX
RSER
8
7
EL Lamp
6
D
5
LX
CIN
6
CS
Supertex inc.
www.supertex.com
HV857
Minimization of EL Lamp Audible Noise
Effect of Series Resistor on EL Lamp
Audible Noise and Brightness
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.
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).
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, RSER,
connected in series with the EL lamp. This waveform has
been proven to generate less noise than a sine wave.
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.
The audible noise from the EL lamp can be set at a desired
level based on the series resistor value used with the 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.
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Supertex inc.
www.supertex.com
HV857
8-Lead DFN Package Outline (K7)
3.00x3.00mm body, 0.80mm height (max), 0.65mm pitch
D2
D
8
8
E
E2
Note 1
(Index Area
D/2 x E/2)
Note 1
(Index Area
D/2 x E/2)
Top View
1
e
b
1
Bottom View
View B
Note 3
θ
A
L
Seating
Plane
A3
A1
L1
Note 2
Side View
View B
Notes:
1. A Pin 1 identifier must be located in the index area indicated. The Pin 1 identifier can be: a molded mark/identifier; an embedded metal marker; or
a printed indicator.
2. Depending on the method of manufacturing, a maximum of 0.15mm pullback (L1) may be present.
3. The inner tip of the lead may be either rounded or square.
Symbol
Dimension
(mm)
A
A1
MIN
0.70
0.00
NOM
0.75
0.02
MAX
0.80
0.05
A3
0.20
REF
b
D
D2
E
E2
0.25
2.85*
1.60
2.85*
1.35
0.30
3.00
-
3.00
-
0.35
3.15*
2.50
3.15*
1.75
e
0.65
BSC
L
L1
θ
0.30
0.00*
0O
0.40
-
-
0.50
0.15
14O
JEDEC Registration MO-229, Variation WEEC-2, Issue C, Aug. 2003.
* This dimension is not specified in the JEDEC drawing.
Drawings not to scale.
Supertex Doc. #: DSPD-8DFNK73X3P065, Version C081109.
Doc.# DSFP-HV857
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8
Supertex inc.
www.supertex.com
HV857
8-Lead MSOP Package Outline (MG)
3.00x3.00mm body, 1.10mm height (max), 0.65mm pitch
D
θ1
8
Note 1
(Index Area
D/2 x E1/2)
E1
E
L2
L
θ
L1
1
Gauge
Plane
Seating
Plane
View B
Top View
View B
A
A A2
Seating
Plane
A1
e
b
Side View
View A-A
A
Note:
1. A Pin 1 identifier must be located in the index area indicated. The Pin 1 identifier can be: a molded mark/identifier; an embedded metal marker; or
a printed indicator.
Symbol
Dimension
(mm)
A
A1
A2
b
D
E
E1
MIN
0.75*
0.00
0.75
0.22
2.80*
4.65*
2.80*
NOM
-
-
0.85
-
3.00
4.90
3.00
MAX
1.10
0.15
0.95
0.38
3.20*
5.15*
3.20*
e
0.65
BSC
L
0.40
0.60
0.80
L1
0.95
REF
L2
0.25
BSC
θ
θ1
0O
5O
-
-
8O
15O
JEDEC Registration MO-187, Variation AA, Issue E, Dec. 2004.
* This dimension is not specified in the JEDEC drawing.
Drawings are not to scale.
Supertex Doc. #: DSPD-8MSOPMG, Version H041309.
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline
information go to http://www.supertex.com/packaging.html.)
Supertex inc. does not recommend the use of its products in life support applications, and will not knowingly sell them for use in such applications unless it receives
an adequate “product liability indemnification insurance agreement.” Supertex inc. does not assume responsibility for use of devices described, and limits its liability
to the replacement of the devices determined defective due to workmanship. No responsibility is assumed for possible omissions and inaccuracies. Circuitry and
specifications are subject to change without notice. For the latest product specifications refer to the Supertex inc. (website: http//www.supertex.com)
Supertex inc.
©2013 Supertex inc. All rights reserved. Unauthorized use or reproduction is prohibited.
Doc.# DSFP-HV857
A062013
9
1235 Bordeaux Drive, Sunnyvale, CA 94089
Tel: 408-222-8888
www.supertex.com
