TK6592x
MEDIUM EL LAMP DRIVER
FEATURES
s
High Ratio of Brightness / Input Power
s
Constant Brightness Versus Input Supply Changes
s
Optimized for 9 nf to 27 nf Panel Capacitance
s
Panel Voltage Slew Rates Controlled for Life
Enhancement
s
Panel Peak to Peak Voltage Independent of Input
Voltage and Temperature
s
Panel Peak to Peak Frequency Independent of
Input Voltage and Temperature
s
s
s
s
s
s
s
s
Miniature Package (SOT23L-6)
Operates with Miniature Coil
Minimum External Components
Laser-Trimmed Fixed Frequency Operation
PWM Control Method
Adjustable Output Voltage
Lower Noise (Audio and EMI)
Split Power Supply Application
APPLICATIONS
s
Battery Powered Systems
s
Cellular Telephones
s
Pagers
s
LCD Modules
s
Wrist Watches
s
Consumer Electronics
The oscillator circuits for the boost converter and lamp
driver are both internally generated in the TK6592x, without
the need for external components. The clock frequency of
the boost converter is laser-trimmed to ensure good initial
accuracy that is relatively insensitive to variations in
temperature and supply voltage. The clock frequency of
the lamp driver tracks the frequency of the boost converter
by a constant scaling factor.
Furthermore, the drive architecture of the TK6592x has
been designed to limit peak drive current delivered to the
lamp. This approach limits the slew rate of the voltage
across the lamp and has the potential to improve lamp life
and decrease RF interference.
The TK6592x is available in a miniature, 6-pin
SOT23L-6 surface mount package
TK6592x
EL+
VCC
GND
IND
DESCRIPTION
The TK6592x Electroluminescent (EL) Lamp Driver has
been optimized for battery controlled systems where power
consumption and size are primary concerns. The miniature
device size (SOT23L-6), together with the miniature Toko
EL coils (D32FU, D31FU, D52FU), further helps system
designers reduce the space required to drive the small EL
panels.
The proprietary architecture (detailed in the Theory of
Operation section) of the TK6592x provides a constant
output power to the lamp, independent of variations in the
battery voltage. This architecture allows the output voltage
to remain relatively constant as battery voltages decay,
without the need for directly sensing the high voltage
output of the EL driver.
20P
HV
EL-
BLOCK DIAGRAM
IND
VCC
HV BOOST
CONTROL
GND
ORDERING INFORMATION
TK6592 MTL
Lamp Frequency Code
OSCILLATOR
HV
EL+
H
BRIDGE
EL-
LAMP FREQUENCY CODE
TK65920
TK65921*
TK65922
TK65923*
TK65924
175 Hz
200 Hz
225 Hz
250 Hz
275 Hz
TK65925*
TK65926
TK65927*
TK65928
TK65929*
300 Hz
325 Hz
350 Hz
375 Hz
400 Hz
TAPE/REEL CODE
TL: Tape Left
* Consult factory for availability
of other frequencies.
May 2000 TOKO, Inc.
Page 1
TK6592x
ABSOLUTE MAXIMUM RATINGS
V
CC
Pin .................................................................... 6.5 V
All Pins Except V
CC
and GND ............................... V
CLAMP
Power Dissipation (Note 1) ................................ 600 mW
Storage Temperature Range ................... -55 to +150
°C
Operating Temperature Range ...................-30 to +80
°C
Junction Temperature ........................................... 150
°C
TK6592x ELECTRICAL CHARACTERISTICS
V
CC
= 3.6 V, T
A
= T
j
= 25
°C,
unless otherwise specified.
SYMBOL
V
CC
I
Q
I
PEAK
F
LAMP
F
BOOST
V
CLAMP
D
(MAX)
V
OUT
I
CONV
PARAMETER
Input Supply Range
Quiescent Current
Peak Current Threshold
Lamp Frequency
Boost Frequency
Boost Clamp Voltage
Maximum Duty Cycle
Peak to Peak Lamp Voltage
Converter Supply Current
TEST CONDITIONS
MIN
2.7
TYP
3.6
MAX
6
200
UNITS
V
µA
mA
Hz
kHz
Current into pin 6
44
52
See Table 1
See Table 2
Force 100 µA into HV pin
90
88
(Note 3)
(Notes 2, 3)
125
105
92
140
See Table 3
60
120
96
155
V
%
V
mA
Note 1: Power dissipation is 600 mW when mounted as recommended (200 mW In Free Air). Derate at 4.8 mW/°C for operation above 25
°C.
Note 2: Converter supply current is dependent upon the DC resistance of inductor L
1
. Lower DC resistances will result in lower supply currents.
Note 3: When using test circuit below.
Gen. Note: Refer to “INDUCTOR VALUE SELECTION” and “INDUCTOR TYPE SELECTION” of Design Considerations Section for choosing
inductor.
TEST CIRCUIT
EL +
HV
EL -
VCC
GND
ICONV
VCC
CEL
12 nF
IND
L1
680 µH
C1
47 nF
D1
Note: L
1
= Toko Low Profile D52FU Series: 875FU-681 M
D
1
= DIODES INC. DL4148
C
1
= AVX 12061C473KAT2A
Page 2
May 2000 TOKO, Inc.
Power technology
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