Endicott Research Group, Inc.
2601 Wayne St., Endicott NY 13760
607-754-9187 Fax 607-754-9255 MT261859
Specifications and
Applications Information
MT261859
The ERG MT261859 (MT Series) dc to ac
inverter is specifically designed to power the
Landmark BL-C054A 5 tube or BL-C061 6
tube LCD backlight module.
The MT261859’s high power density,
dimming control, and encapsulated package
make it the ideal power source for applica-
tions where high efficiency and reliability in
lighting multiple tube backlights are critical.
5 or 6 Tube
DC to AC Inverter
Preliminary
Package Configuration
(Bottom View)
4
page 8
+V
11 12 13 14 15 3
Gnd
1
2
CT
PWM
FREQ.
RR
PWM RANGE
(OPTIONAL)
INTENSITY
+V
OPTIONAL (LIMITS MINIMUM DUTY CYCLE)
5
6
7
8
9
4
10
7/11/96
1.000
5.130
1.720
.250
.150
10 9 8 765
11
12
.750
FIGURE 10
TYPICAL CONNECTION TO BL-C061 UTILIZING INTERNAL PWM GENERATOR
Landmark BL-C061
Backlight Assembly
2.200
2.350
2.650
3.200
3.600
3.700
4.400
.800
.600
.400
.200
.175
.550
.500
.350
.100
21
13 3
14
15
1) +12 Vdc
2) Gnd
3) Control
4) ACCOMMON
5) Tube 1
6) Tube 2
7) Tube 3
8) Tube 4
9) Tube 5
10) Tube 6
11) CT1
12) CT2
13) PWM Control Range
14) PWM Control
15) PWM Out
Pinout
FIGURE 9 - CONNECTION SCHEME WHEN POWERING BL-C054A
page 2 page 7
MT261859 MT261859
1
2
11 312 13 14 15
+12V
5.641V
Gnd
PWM OUT
180Hz
50% DUTY CYCLE 5.55mS
2.775mS
10.8VP-P
10KΩ
.3uF
CT
FIGURE 8 - PWM TEST CIRCUIT
5
6
7
8
9
4
10
The MT261859 is a DC/AC inverter designed to power 6 CCFT tubes. External shutdown
control and an internal PWM generator provides the user the ability to do anything from a
simple disable function to simultaneous dimming control of all 6 tubes.
The external shutdown control (pin 3) is a TTL compatibile input that turns off all 6 tubes
when pulled low. On-board dimming control is accomplished by connecting this pin to the
internal PWM generator (pin 19).
The frequency of the internal PWM generator is set by one external capacitor connected
between pins 15 and 16. Experience has shown that, in most cases, a PWM frequency 2.5
times that of the frame rate of the LCD will not produce beat frequency interference
(asynchronous operation).
A variable dc level applied to pin 18 changes the duty cycle of the PWM generator and
hence the intensity of the CCFT’s. The DC range of this input can be varied, if desired, via
a resistor placed from pin 17 to ground.
In most cases it will be found that dimming under 10% duty cycle will produce uneven
lighting/flickering of the tubes and/or their reluctance to all stay lit under temperature
ranges beyond 25° C. This is a function of both the parasitics of the CCFT wiring/assembly
and limitations in the CCFT’s ability to maintain a minimum internal temperature. It should
be noted that, for most applications, these low light levels should not be required. By
limiting the max dc level applied to pin 18, the minimum brightness level can be set.
If tighter control over the PWM rate is required (synchronous operation), application of an
external variable duty cycle square wave to pin 3 that is synchronized to the frame rate of
the LCD and in most cases twice its frequency will satisfy more critical applications. Pins
15-19 can be left floating when external control is employed.
The MT261859 can also be used to power the Landmark BL-C054A 5 tube backlight
module, in which case the unused output should be tied to the AC common output (pin 4)
as shown in Figure 9.
NARRATIVE
Typical Performance Curves
(No Dimming)
MT261859 MT261859
page 6 page 3
INVERTER
SECTION
INTERNAL PWM
GENERATOR
FIGURE 1 - ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings
Rating Symbol Value Units
I nput Voltage Range Vin -0.3 to +15 Vdc
Operat ing Temperature To 0 to +70 °C
S tora ge Tempera tur e Tstg -40 to +85 °C
Recommended Operating Conditions
Rating Symbol Value Units
I nput Voltage Vin +10.8 to 13.2 Vdc
Electrical Characteristics
Unless otherwise noted Vin = 12.00 Volts dc and Ta = 25°C.
Characteristic Symbol Min Typ Max Units
I nput Curr ent
BL-C061 Back light (6 tubes)
BL-C054A Bac k light ( 5 tubes)
Iin -1.04
.875
-Adc
O perating Frequenc y Fo - 25 - KHz
T ube Starting Volt age * Vstart 1125 - - Vrms
Efficiency η-84 -%
O utput Cur rent ( per tube)
BL-C061 Back light (6 tubes)
BL-C054A Bac k light ( 5 tubes)
Iout -4.25
4.25
-marms
O ut put Voltage **
BL-C061 Back light
BL-C054A Bac k light
Vout - 410
410
-Vrms
CCFT Control Level ( P in 3)
CCFT Output Off
CCF T Output On 2.2 1.5 Vdc
CCFT Contr ol Pin
Sink Current 1.1 1.4 madc
PWM Frequency Range 50 1000 Hz
PWM Frequency *** 180 Hz
PWM Cont r ol Voltage (P in 14) 0 +Vin-2 Vdc
I nput Bias Current (P in 14) 45 250 nAdc
PWM Contr ol Range
Program Re sistance (Pin 13) 1Kohm
PWM O utput Level (Pin 15)
Low
High 10 5
11 50 mVdc
Vdc
* Vali d over entire operating temp. range
*** CT = .3u F Across Pins 11 & 12 , se e test ckt. Fig ure 3 ** M easured, not guaranteed
FIG URE 6 - T UBE F REQUENCY V S. I NPUT V OLTAGE
I NPUT VOLTAGE ( Vdc)
RELATIVE FREQUENCY
-2.0%
-1.0%
0.0%
1.0%
2.0%
3.0%
4.0%
10.50 11.00 11.50 12.00 12.50 13.00 13.50
FIG URE 7 - T UBE CURRENT v s. I NPUT VOLTAGE
I NPU T VO LTAGE
RELATIVE TUBE CURRENT
75.0%
80.0%
85.0%
90.0%
95.0%
100.0%
105.0%
110.0%
115.0%
10.50 11.00 11.50 12.00 12.50 13.00 13.50
SHUT-DOWN
SECTION
FI GURE 3 - P WM CONT ROL VOLTAGE VS. RANGE RESISTANCE
PWM CONTROL RANGE RESIST ANCE (KOHMS)
PWM CONTROL VOLTAGE
(VOLTS)
0
1
2
3
4
5
6
7
8
9
10
0 102030405060708090100
0 % DUTY CYCLE 50 % DUTY CYCLE 1 00% DUTY CYCLE
F IGURE 4 - PWM FREQ UENCY VS. TI MING CAPACITOR VALUE
TIMING CAPACITOR - CT (uF)
PWM FREQUENCY (Hz)
0
100
200
300
400
500
600
700
800
900
1000
0 0.2 0.4 0.6 0.8 1 1.2
FIGURE 5 - PWM CONTROL VOLTAGE VS. D UTY CYCLE
PWM CONTROL VOLTAGE (VOLTS)
DUTY CYCLE (%)
0
10
20
30
40
50
60
70
80
90
100
12345678910
(PIN 18)
(ACROSS PINS 15 & 16)
FIG URE 2 - PWM CONTROL VOLTA GE SHIFT vs. PWM FREQUENCY
PWM FREQUENCY (Hz)
PWM CONTROL VOLTAGE
5.25
5.3
5.35
5.4
5.45
5.5
5.55
5.6
5.65
5.7
0 100 200 300 400 500 600 700 800 900 1000
(MAINTAINING 50% DUTY CYCLE)
VIN= 12Vdc
RR = OPEN
VIN= 12Vdc
Pin 17 floating
CT = .3uF (PWM Freq. = 180Hz)
VIN= 12Vdc
CT = .3uF
MT261859 MT261859
page 4 page 5
VIN= 12Vdc
Pin 17 floating
PWM cntl (pin 18) = 5.641V (50% D.C.)
CT (uF) = 52 / Freq.
