LTC1426 Datasheet, PDF (1/8 Pages) Linear Technology – Micropower Dual 6-Bit PWM DAC

FEATURES
s _{Wide Supply Range: 2.7V ≤ VCC ≤ 5.5V}
s _{Wide Reference Voltage Range: 0V to 5.5V}
s _{Two Interface Modes:}
Pulse Mode (Increment Only)
Pushbutton Mode (Increment/Decrement)
s _{Low Supply Current: 50µA}
s _{0.2µA Supply Current in Shutdown}
s _{Available in 8-Pin MSOP and SO Packages}
s _{DAC Contents Are Retained in Shutdown}
s _{DACs Power-Up at Midrange}
s _{Low Output Impedance: < 100Ω}
s _{Output Frequency: 5kHz Typ}
U
APPLICATIONS
s _{LCD Contrast and Backlight Brightness Control}
s _{Power Supply Voltage Adjustment}
s _{Battery Charger Voltage and Current Adjustment}
s _{GaAs FET Bias Adjustment}
s _{Trimmer Pot Elimination}
LTC1426
Micropower
Dual 6-Bit PWM DAC
DESCRIPTION
The LTC^®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 50µA and drops to 0.2µA 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.
TYPICAL APPLICATION
Pushbutton Adjustable CCFL/LCD Contrast Generator
UP TO 6mA
LAMP
R_P1
47k
UP
DOWN
R_P2
47k
R_SHDN
1M
SHDN
UP CONTRAST
LTC1426
UP/DOWN 1
8
CLK1 SHDN
CCFL UP/DOWN 2
7
CLK2 V_CC
3
6
DOWN
GND V_REF
4
5
PWM1 PWM2
R3
R4
5.1k
4.99k
1%
1%
C3
10µF
R1
5V
44.2k
1%
C1
0.1µF
R5
20k
1%
C4
0.1µF
R6
40k
1%
R2
44.2k
1%
C2
1µF
I_CCFL = 0µA TO 50µA
HIGH VOLTAGE
ROYER
1
16
CCFL PGND CCFL V_SW
2
15
I_CCFL
BULB
3
14
DIO LT1182 BAT
C7 1µF
4
CCFL V_C
5
AGND
6
SHDN
13
ROYER
12
V_IN
11
FBP
7
LCD V_C
R7 8
C8 _10k LCD PGND
0.68µF
10
FBN
9
LCD V_SW
5V
C9
2.2µF
8V TO
28V
+ C10
2.2µF
35V
+ C11
2.2µF
35V
CONSULT THE LT1182 DATA SHEET FOR
DETAILS ON THE HIGH VOLTAGE ROYER
AND LCD CONTRAST CONVERTER SECTIONS
LCD
CONTRAST
CONVERTER
V_OUT
NEGATIVE
1426 TA01
LCD CONTRAST
V_OUT = –10V TO –30V
1