LTC1428-50_15 Datasheet, PDF (1/8 Pages) Linear Technology – Micropower 8-Bit Current Sink Output D/A Converter

LTC1428-50
Micropower 8-Bit Current
Sink Output D/A Converter
FEATURES
s _{Precision Full-Scale DAC Output Current}
at 25°C: 50µA ±3%
s _{Wide Output Voltage DC Compliance: 2V to 10V}
s _{Wide Supply Range: 3V ≤ VCC ≤ 6.5V}
s _{Supply Current in Shutdown: 0.2µA}
s _{Low Supply Current: 130µA}
s _{Available in 8-Pin SO}
s _{Triple Mode}^TM _Interface
1. Standard 3-Wire Mode
2. 1-Wire Pulse Mode Interface: Increment-Only
3. 2-Wire Pulse Mode Interface: Increment/Decrement
s _{DAC Value Read Back Capability in 3-Wire Mode}
s _{DAC Powers Up at Midrange}
s _{DAC Contents Are Retained in Shutdown}
U
APPLICATIONS
s _{LCD Contrast Control}
s _{Backlight Brightness Control}
s _{Power Supply Voltage Adjustment}
s _{Battery Charger Voltage/Current Adjustment}
s _{GaAs FET Bias Adjustment}
s _{Trimmer Pot Elimination}
DESCRIPTION
The LTC^®1428-50 is a micropower 8-bit current sink
output D/A converter (DAC) with an output range of 0µA to
50µA. In 3.3V or 5V systems, the DAC I_OUT pin can be
biased from 2V to 10V. Supply current is only 130µA.
Shutdown mode drops the supply current to 0.2µA.
The LTC1428-50 communicates with external circuitry by
using one of three interface modes: standard 3-wire serial
mode or one of two pulse modes. Upon power-up, the
internal counter resets to 10000000B, the DAC output
assumes midrange and the chip configures to 3-wire or
pulse mode depending on the CS signal level.
In 3-wire mode, the system MPU can serially transfer
8-bit data to and from the LTC1428-50. In pulse mode, the
upper six bits of the DAC output program for increment-
only (1-wire interface) or increment/decrement (2-wire
interface) operation depending on the D_IN signal level. In
increment-only mode, the counter rolls over and sets the
DAC to zero if the counter increases beyond full scale. In
increment/decrement mode, the counter stops
incrementing at full scale, stops decrementing at zero
scale and does not roll over.
LTC1428-50 is available in an 8-pin SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Triple Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATION
Digitally Controlled LCD Bias Generator (Standard 3-Wire Mode)
L1
D1
2
CELLS
R1
240k
V_IN
SHDN
SHDN
SW
LT^®1307
R2
1µF
FB
22k
GND V_C
4700pF
R3
22k
100k
L1: 4.7µH MURATA-ERIE LQH3C
D1: MBR0530 OR 1N4148
V_OUT
15.75V TO 27.75V IN STEPS OF 47mV
15mA FROM 2 CELLS
C1
0.1µF
1
I_OUT
2
V_CC
8
D_OUT
7
D_IN
LTC1428-50
3
SHDN
6
GND
4
CLK
5
CS
5V
V_CC
MPU
(e.g., 8051)
1428-50 TA01
P1.3
P1.2
P1.1
P1.0
1