LTC1426
Micropower
Dual 6-Bit PWM DAC
FEATURES
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DESCRIPTION
The LTC
廬
1426 is a dual micropower 6-bit PWM DAC
featuring versatile PWM outputs and a flexible pushbutton
compatible digital interface. The DAC outputs provide a
PWM signal that swings from 0V to V
REF
, allowing the full-
scale output to be varied by adjusting the voltage at V
REF
.
The PWM output frequency is typically 5kHz, easing
output filtering requirements. V
CC
supply current is typi-
cally 50碌A(chǔ) and drops to 0.2碌A(chǔ) in shutdown.
The LTC1426 can be controlled using one of two interface
modes: pushbutton and pulse. The LTC1426 automati-
cally configures itself into the appropriate mode at start-
up by monitoring the state of the CLK pins. In pushbutton
mode, the CLK pins can be directly connected to external
pushbuttons to control the DAC output. In pulse mode,
the CLK pins can be connected to CMOS compatible
logic. The DAC outputs initially power up at half scale and
the contents of the internal DAC registers are retained in
shutdown.
The LTC1426 is available in 8-pin MSOP and SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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Wide Supply Range: 2.7V
鈮?/div>
V
CC
鈮?/div>
5.5V
Wide Reference Voltage Range: 0V to 5.5V
Two Interface Modes:
Pulse Mode (Increment Only)
Pushbutton Mode (Increment/Decrement)
Low Supply Current: 50碌A(chǔ)
0.2碌A(chǔ) Supply Current in Shutdown
Available in 8-Pin MSOP and SO Packages
DAC Contents Are Retained in Shutdown
DACs Power-Up at Midrange
Low Output Impedance: < 100鈩?/div>
Output Frequency: 5kHz Typ
APPLICATIONS
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LCD Contrast and Backlight Brightness Control
Power Supply Voltage Adjustment
Battery Charger Voltage and Current Adjustment
GaAs FET Bias Adjustment
Trimmer Pot Elimination
TYPICAL APPLICATION
Pushbutton Adjustable CCFL/LCD Contrast Generator
UP TO 6mA
LAMP
HIGH VOLTAGE
ROYER
16
15
14
13
12
11
10
9
5V
C9
2.2碌F
8V TO
28V
5V
R1
44.2k
1%
C1
0.1碌F
R2
44.2k
1%
C2
1碌F
C7 1碌F
I
CCFL
= 0碌A(chǔ) TO 50碌A(chǔ)
1
2
3
4
5
6
7
CCFL PGND CCFL V
SW
I
CCFL
DIO
CCFL V
C
AGND
SHDN
LCD V
C
LT1182
BULB
BAT
ROYER
V
IN
FBP
FBN
LCD V
SW
R
P1
47k
UP
R
P2
47k
UP CONTRAST
UP/DOWN 1
CCFL UP/DOWN 2
3
R
SHDN
1M
SHDN
LTC1426
CLK1
CLK2
GND
SHDN
V
CC
V
REF
8
7
6
5
R5
20k
1%
DOWN
DOWN
4
PWM1 PWM2
R3
5.1k
1%
R4
4.99k
1%
C3
10碌F
R7 8
C8 10k
LCD PGND
0.68碌F
C4
0.1碌F
R6
40k
1%
CONSULT THE LT1182 DATA SHEET FOR
DETAILS ON THE HIGH VOLTAGE ROYER
AND LCD CONTRAST CONVERTER SECTIONS
U
U
U
+
C10
2.2碌F
35V
+
C11
2.2碌F
35V
LCD
CONTRAST
CONVERTER
V
OUT
NEGATIVE
LCD CONTRAST
V
OUT
= 鈥?0V TO 鈥?0V
1426 TA01
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