Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsData collecting ICsData acquisition IC - DA converter (DAC) SOIC 8

LTC1427-50

Micropower, 10-Bit Current

Output DAC with SMBus

Serial Interface

1

2

3

8

7

6

1427 TA02

C1

1µF

4700pF



3.3V

OUT

= 12.7V TO 24V IN 11mV STEPS

 15mA (2 CELLS)

 35mA ( 3 CELLS)

L1 =10 µH SUMIDA CD43

 MURATA-ERIE LQH3C

 OR COILCRAFT DO1608

D1 =MBR0530

100k

2 TO 4

CELLS

LTC1427-50

R1

226k

R2

12.1k

SHDN

AD1

AD0

GND



OUT



SCL

SDA

P1.2

P1.1

P1.0

GND

LT1317



SHDN

µPU

(e.g., 8051)

TYPICAL APPLICATION

Digitally Controlled LCD Bias Generator

FEATURES

DESCRIPTION

■

LCD Contrast and Backlight Brightness Control

■

Power Supply Voltage Adjustment

■

Battery Charger Voltage/Current Adjustment

■

GaAs FET Bias Adjustment

■

Trimmer Pot Elimination

The LTC

1427-50 is a micropower, 10-Bit current output

DAC with an output range of 0µA to 50µA. The DAC output is

guaranteed monotonic and DNL is less than 0.9LSB under all

operating conditions. Full-scale accuracy is ±2.5% over

the commercial temperature range. The LTC1427-50 oper-

ates with power supply voltages from 2.7V to 5.5V and the

DAC current source output can be biased from (V

– 1.3V)

to –15V.

The LTC1427-50 communicates with external circuitry by

using the SMBus serial interface. It acts as an SMBus slave

device using one of four selectable SMBus addresses set by

the two address pins AD0 and AD1 .

On power-up, the DAC output assumes midrange or zero

scale, depending on the logic state of the two address pins.

The LTC1427-50 can be shut down through the SHDN pin or

by setting the SHDN bit = 1 in the SMBus command byte.

Digital data for the DAC output is retained internally and the

supply current drops to 10µA typically when in shutdown.

The LTC1427-50 is available in an 8-pin SO package.

APPLICATIONS

■

Precision 50

1.5% Initial Full-Scale Output

Current,

2.5% Over Temperature

■

Wide Output Voltage DC Compliance: –15V to

– 1.3V)

■

Wide Supply Range: 2.7V ≤ V

≤ 5.5V

■

Supply Current in Shutdown: 10µA Typ

■

Low Supply Current: 115µA Typ

■

Available in 8-Pin SO

■

SMBus Serial Interface

■

Four Selectable SMBus Addresses

■

DAC Powers Up at Zero or Midscale

■

DAC Contents Are Retained in Shutdown

, LTC and LT are registered trademarks of Linear Technology Corporation.

Summary of content (8 pages)

PAGE 1
LTC1427-50 Micropower, 10-Bit Current Output DAC with SMBus Serial Interface U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Precision 50µA, ± 1.5% Initial Full-Scale Output Current, ±2.5% Over Temperature Wide Output Voltage DC Compliance: – 15V to (VCC – 1.3V) Wide Supply Range: 2.7V ≤ VCC ≤ 5.
PAGE 2
LTC1427-50 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) ORDER PART NUMBER TOP VIEW Total Supply Voltage (VCC) ........................................ 7V Input Voltage (All Inputs)............. – 0.3V to (VCC + 0.3V) DAC Output Voltage ...................... – 15V to (VCC + 0.3V) DAC Output Short-Circuit Duration .................. Indefinite Operating Ambient Temperature Range ....... 0°C to 70°C Junction Temperature ..........................................
PAGE 3
LTC1427-50 U U U U WW RECO E DED OPERATI G CO DITIO S VCC = 3.3V, TA = operating temperature range unless otherwise specified. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 100 kHz SMBus Timing (Notes 2, 3) fSMB SMB Operating Frequency ● 10 tBUF Bus Free Time Between Stop and Start Condition ● 4.7 µs tHD:STA Hold Time After (Repeated) Start Condition ● 4.0 µs tSU:STA Repeated Start Condition Setup Time ● 4.7 µs tSU:STO Stop Condition Setup Time ● 4.
PAGE 4
LTC1427-50 U W TYPICAL PERFORMANCE CHARACTERISTICS Full-Scale Current vs Temperature Zero-Scale Current vs Temperature 52 0.02 V(IOUT) = 0V 0 51 OUTPUT CURRENT (µA) OUTPUT CURRENT (µA) –0.02 –0.04 –0.06 –0.08 –0.10 –0.12 50 49 –0.14 –0.16 V (IOUT) = 0V –0.18 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) 48 –50 –25 150 0 25 50 75 100 125 1427 G04 1427 G03 Bias Voltage Rejection (Zero-Scale Current) Bias Voltage Rejection (Full-Scale Current) 1.0 TA = 25°C VCC = 3.
PAGE 5
LTC1427-50 U U U PIN FUNCTIONS SHDN (Pin 1): Shutdown. A logic low puts the chip into shutdown mode. In shutdown, the digital settings for the DAC are retained. On release from shutdown, the previously programmed value for IOUT is reinstated. AD1, AD0 (Pins 2, 3): Address Selection Pins. Tie these two pins to either VCC or GND to select one of four SMBus addresses to which the LTC1427-50 will respond. GND (Pin 4): Ground. Ground should be tied directly to a ground plane.
PAGE 6
LTC1427-50 WU W TI I G DIAGRA S Timing for SMBus Interface t BUF SDA t HD:STA t HD:STA tf tr SCL t LOW STOP t HIGH START t SU:STO t SU:STA t HD:DAT t SU:DAT 1427 TD01 START STOP Operating Sequence SMBus Write Byte Protocol, with SMBus Address = 0101111B, Command Byte = 0XXXXX11B and Data Byte = 11111111B VCC AD1 GND VCC AD0 GND SCL S 1 2 3 1 1 4 5 1 6 1 7 X X X X 1 1 1 1 1 1 1 1 1 1 * P 9 8 X ACK 0 DATA BYTE ACK 1 ACK 0 WR SDA COMMAND BYTE SHDN SMBUS ADDR
PAGE 7
LTC1427-50 U U W U APPLICATIONS INFORMATION mand code and data byte are defined with the following format: Command Byte 7 Data Byte 6 5 4 3 2 1 0 SHDN X X X X X D9 D8 7 6 5 4 3 2 1 0 D7 D6 D5 D4 D3 D2 D1 D0 SHDN: 0 for Normal Operation, 1 for Shutdown D9 to D0: DAC Data Bits, D9 is the Most Significant Bit The Slave Address The LTC1427-50 can respond to one of four 7-bit addresses. The first five bits have been factory programmed to 01011.
PAGE 8
LTC1427-50 U TYPICAL APPLICATIONS SMBus-Controlled Floating CCFL Power Supply UP TO 6mA LAMP ALUMINUM ELECTROLYTIC IS RECOMMENDED FOR C3B WITH AN ESR ≥ 0.5Ω TO PREVENT DAMAGE TO THE LT1184F HIGH-SIDE SENSE RESISTOR DUE TO SURGE CURRENTS AT TURN-ON. 10 L1 C1 MUST BE A LOW LOSS CAPACITOR, C1 = WIMA MKP-20 Q1, Q2 = ZETEX ZTX849 OR ROHM 2SC5001 L1 = COILTRONICS CTX210605 L2 = COILTRONICS CTX100-4 *DO NOT SUBSTITUTE COMPONENTS COILTRONICS (407) 241-7876 3 C5 1000pF VCC 3.3V C6 0.