Datasheet

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LTC1096/LTC1096L

LTC1098/LTC1098L

Micropower Sampling

8-Bit Serial I/O A/D Converters

ESCRIPTIO

■

80µA Maximum Supply Current

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1nA Typical Supply Current in Shutdown

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8-Pin SO Plastic Package

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5V Operation (LTC1096/LTC1098)

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3V Operation (LTC1096L/LTC1098L)(2.65V Min)

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Sample-and-Hold

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16µs Conversion Time

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33kHz Sample Rate

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±0.5LSB Total Unadjusted Error Over Temp

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Direct 3-Wire Interface to Most MPU Serial Ports and

All MPU Parallel I/O Ports

The LTC

1096/LTC1096L/LTC1098/LTC1098L are

micropower, 8-bit A/D converters that draw only 80µA of

supply current when converting. They automatically power

down to 1nA typical supply current whenever they are not

performing conversions. They are packaged in 8-pin SO

packages and have both 3V (L) and 5V versions. These

8-bit, switched-capacitor, successive approximation ADCs

include sample-and-hold. The LTC1096/LTC1096L have a

single differential analog input. The LTC1098/LTC1098L

offer a software selectable 2-channel MUX.

On-chip serial ports allow efficient data transfer to a wide

range of microprocessors and microcontrollers over three

wires. This, coupled with micropower consumption, makes

remote location possible and facilitates transmitting data

through isolation barriers.

These circuits can be used in ratiometric applications or

with an external reference. The high impedance analog

inputs and the ability to operate with reduced spans

(below 1V full scale) allow direct connection to sensors

and transducers in many applications, eliminating the

need for gain stages.

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Battery-Operated Systems

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Remote Data Acquisition

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Battery Monitoring

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Battery Gas Gauges

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Temperature Measurement

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Isolated Data Acquisition

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

Supply Current vs Sample Rate

SAMPLE FREQUENCY, f

SMPL

(kHz)

0.1

SUPPLY CURRENT, I

(µA)

100

1000

1 10 100

LTC1096/98 • TPC03



= 25°C

= V

REF

= 5V

10µW, S8 Package, 8-Bit A/D

Samples at 200Hz and Runs Off a 5V Battery

5V1µF

ANALOG INPUT

0V TO 5V RANGE



–IN

GND

CLK

OUT

REF

LTC1096

MPU

(e.g., 8051)

P1.4

P1.3

P1.2

+IN



LTC1096/8 • TA01

CS/

SHUTDOWN

ITY

Summary of content (28 pages)

PAGE 1
LTC1096/LTC1096L LTC1098/LTC1098L Micropower Sampling 8-Bit Serial I/O A/D Converters U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 80µA Maximum Supply Current 1nA Typical Supply Current in Shutdown 8-Pin SO Plastic Package 5V Operation (LTC1096/LTC1098) 3V Operation (LTC1096L/LTC1098L)(2.65V Min) Sample-and-Hold 16µs Conversion Time 33kHz Sample Rate ±0.
PAGE 2
LTC1096/LTC1096L LTC1098/LTC1098L W W W AXI U U ABSOLUTE RATI GS (Notes 1 and 2) Operating Temperature LTC1096AC/LTC1096C/LTC1096LC/ LTC1098AC/LTC1098C/LTC1098LC ....... 0°C to 70°C LTC1096AI/LTC1096I/LTC1096LI/ LTC1098AI/LTC1098I/LTC1098LI ..... – 40°C to 85°C Lead Temperature (Soldering, 10 sec.)................ 300°C Supply Voltage (VCC) to GND ................................... 12V Voltage Analog and Reference ................ –0.3V to VCC + 0.3V Digital Inputs .................................
PAGE 3
LTC1096/LTC1096L LTC1098/LTC1098L U U U U WW RECO E DED OPERATI G CO DITIO S LTC1096/LTC1098 SYMBOL PARAMETER CONDITIONS MIN t WLCLK t WHCS t WLCS TYP MAX UNITS CLK Low Time VCC = 5V 0.
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LTC1096/LTC1096L LTC1098/LTC1098L U U W CO VERTER A D ULTIPLEXER CHARACTERISTICS LTC1096/LTC1098 VCC = 5V, VREF = 5V, fCLK = 500kHz, unless otherwise noted. PARAMETER LTC1096A/LTC1098A MIN TYP MAX CONDITIONS LTC1096/LTC1098 MIN TYP MAX Resolution (No Missing Code) ● Offset Error ● ±0.5 ±0.5 LSB ● ±0.5 ±0.5 LSB ● ±0.5 ±1.0 LSB ● ±0.5 ±1.0 LSB Linearity Error (Note 4) Full Scale Error Total Unadjusted Error (Note 5) VREF = 5.
PAGE 5
LTC1096/LTC1096L LTC1098/LTC1098L U DIGITAL AND DC ELECTRICAL CHARACTERISTICS LTC1096/LTC1098 VCC = 5V, VREF = 5V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS VIH High Level Input Voltage VCC = 5.25V ● MIN TYP MAX VIL Low Level Input Voltage VCC = 4.75V ● IIH High Level Input Current VIN = VCC IIL Low Level Input Current VIN = 0V VOH High Level Output Voltage VCC = 4.75V, IO = 10µA VCC = 4.75V, IO = 360µA ● ● VOL Low Level Output Voltage VCC = 4.75V, IO = 1.6mA ● 0.
PAGE 6
LTC1096/LTC1096L LTC1098/LTC1098L U DIGITAL AND DC ELECTRICAL CHARACTERISTICS LTC1096L/LTC1098L VCC = 2.65V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX VIH High Level Input Voltage VCC = 3.6V ● VIL Low Level Input Voltage VCC = 2.65V ● 0.45 V IIH High Level Input Current VIN = VCC ● 2.5 µA IIL Low Level Input Current VIN = 0V ● – 2.5 µA VOH High Level Output Voltage VCC = 2.65V, IO = 10µA VCC = 2.
PAGE 7
LTC1096/LTC1096L LTC1098/LTC1098L AC CHARACTERISTICS LTC1096/LTC1098 VCC = 3V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted. SYMBOL PARAMETER CONDITIONS tSMPL Analog Input Sample Time See Operating Sequence MIN fSMPL(MAX) Maximum Sampling Frequency TYP MAX 1.5 ● UNITS CLK Cycles 16.
PAGE 8
LTC1096/LTC1096L LTC1098/LTC1098L U W TYPICAL PERFOR A CE CHARACTERISTICS Supply Current vs Clock Rate for Active and Shutdown Modes VCC = 9V SUPPLY CURRENT, ICC (µA) SUPPLY CURRENT, ICC (µA) 200 150 VCC = 5V 100 50 10 0.002 0 CS = VCC TA = 25°C VREF = 2.5V TA = 25°C VCC = VREF = 5V 80 60 “ACTIVE” MODE CS = 0 40 20 10 1 0 1000 100 “SHUTDOWN” MODE CS = VCC 0.
PAGE 9
LTC1096/LTC1096L LTC1098/LTC1098L U W TYPICAL PERFOR A CE CHARACTERISTICS Maximum Clock Frequency vs Source Resistance 1.5 VIN + INPUT – INPUT 0.75 RSOURCE– 0.50 0.25 5 TA = 25°C VREF = 2.5V 1.25 TA = 25°C 4 LOGIC THRESH0LD (V) TA = 25°C VCC = VREF = 5V MAXIMUM CLOCK FREQUENCY (MHz) 1.0 0.75 0.5 10 1 1 0.25 0 100 2 RSOURCE – (kΩ) 4 1000 MINIMUM WAKE-UP TIME (µs) TA = 25°C VREF = 5V 1 0 2 6 8 4 SUPPLY VOLTAGE, VCC (V) VREF = 5V VCC = 5V 100 7.5 5.0 RSOURCE+ VIN 2.
PAGE 10
LTC1096/LTC1096L LTC1098/LTC1098L U U U PI FU CTIO S LTC1096/LTC1096L LTC1098/LTC1098L CS/SHDN (Pin 1): Chip Select Input. A logic low on this input enables the LTC1096/LTC1096L. A logic high on this input disables the LTC1096/LTC1096L and disconnects the power to the LTC1096/LTC1096L. CS/SHDN (Pin 1): Chip Select Input. A logic low on this input enables the LTC1098/LTC1098L. A logic high on this input disables the LTC1098/LTC1098L and disconnects the power to the LTC1098/LTC1098L.
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LTC1096/LTC1096L LTC1098/LTC1098L TEST CIRCUITS On and Off Channel Leakage Current Load Circuit for tdDO, tr and tf 5V 1.
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LTC1096/LTC1096L LTC1098/LTC1098L TEST CIRCUITS Voltage Waveforms for ten LTC1096/LTC1096L CS t WAKEUP 1 CLK B7 DOUT VOL ten LTC1098/LTC1098L LTC1096/98 • TC07 CS START DIN 1 CLK 2 3 4 5 B7 DOUT VOL ten U W U UO APPLICATI S I FOR ATIO OVERVIEW The LTC1096/LTC1096L/LTC1098/LTC1098L are 8-bit micropower, switched-capacitor A/D converters. These sampling ADCs typically draw 120µA of supply current when sampling up to 33kHz.
PAGE 13
LTC1096/LTC1096L LTC1098/LTC1098L W U U UO APPLICATI S I FOR ATIO Power Down and Wake-Up Time tWAKEUP CS The LTC1096(L)/LTC1098(L) draw power when the CS pin is low and shut themselves down when that pin is high. In order to have a correct conversion result, a 10µs wake-up time must be provided from CS falling to the first falling clock (CLK) after the first rising CLK for the LTC1096(L) and from CS falling to the MSBF bit CLK falling for the LTC1098(L) (see Operating Sequence).
PAGE 14
LTC1096/LTC1096L LTC1098/LTC1098L U W U UO APPLICATI S I FOR ATIO MSB-FIRST DATA (MSBF = 1) tCYC CS POWER DOWN tWAKEUP CLK tsuCS ODD/ SIGN START DIN DON'T CARE MSBF SGL/ DIFF DOUT NULL BIT B7 B6 (MSB) HI-Z tSMPL B5 B4 B3 B2 Hi-Z B0* B1 tCONV MSB-FIRST DATA (MSBF = 0) tCYC CS POWER DOWN tWAKEUP CLK tsuCS ODD/ SIGN START DIN DON'T CARE SGL/ DIFF DOUT HI-Z tSMPL MSBF NULL B6 BIT B7 (MSB) B5 B4 B3 B2 B0 B1 B1 B2 B3 B4 B5 B6 B7* tCONV Hi-Z LTC1096/98 F02 *AFTER C
PAGE 15
LTC1096/LTC1096L LTC1098/LTC1098L W U U UO APPLICATI S I FOR ATIO the A/D conversion result is output on the DOUT line. Bringing CS high resets the LTC1096(L) for the next data exchange. Input Data Word The LTC1096(L) requires no DIN word. It is permanently configured to have a single differential input. The conversion result, in which output on the DOUT line is MSB-first sequence, followed by LSB sequence providing easy interface to MSB- or LSB-first serial ports.
PAGE 16
LTC1096/LTC1096L LTC1098/LTC1098L W U U UO APPLICATI S I FOR ATIO MSBF BIT LATCHED BY LTC1098(L) CS 1 2 3 4 START SGL/DIFF ODD/SIGN MSBF CLK DATA (DIN/DOUT) B7 MPU CONTROLS DATA LINE AND SENDS MUX ADDRESS TO LTC1098(L) • • • B6 LTC1098(L) CONTROLS DATA LINE AND SENDS A/D RESULT BACK TO MPU PROCESSOR MUST RELEASE DATA LINE AFTER 4TH RISING CLK AND BEFORE THE 4TH FALLING CLK LTC1098(L) TAKES CONTROL OF DATA LINE ON 4TH FALLING CLK LTC1-96/8 • F03 Figure 3.
PAGE 17
LTC1096/LTC1096L LTC1098/LTC1098L U W U UO APPLICATI S I FOR ATIO the converter will draw current. This current may be larger than the typical supply current. It is worthwhile to bring the CS pin all the way to ground when it is low and all the way to supply voltage when it is high to obtain the lowest supply current. When the CS pin is high (= supply voltage), the converter is in shutdown mode and draws only leakage current.
PAGE 18
LTC1096/LTC1096L LTC1098/LTC1098L W U U UO APPLICATI S I FOR ATIO (Figure 6) and connect the center point to the MPU input. It should be noted that to get full shutdown, the CS input of the LTC1096/LTC1098 must be driven to the VCC voltage. This would require adding a level shift circuit to the CS signal in Figure 6. 9V OPTIONAL LEVEL SHIFT The VCC pin should be bypassed to the ground plane with a 1µF tantalum with leads as short as possible.
PAGE 19
LTC1096/LTC1096L LTC1098/LTC1098L U W U UO APPLICATI S I FOR ATIO in and continues until the falling CLK edge after the MSBF bit is received. On this falling edge, the S&H goes into hold mode and the conversion begins. Differential Inputs With differential inputs, the ADC no longer converts just a single voltage but rather the difference between two voltages.
PAGE 20
LTC1096/LTC1096L LTC1098/LTC1098L U W U UO APPLICATI S I FOR ATIO cycle. Large external source resistors and capacitances will slow the settling of the inputs. It is important that the overall RC time constants be short enough to allow the analog inputs to completely settle within the allowed time. RC Input Filtering It is possible to filter the inputs with an RC network as shown in Figure 9. For large values of CF (e.g.
PAGE 21
LTC1096/LTC1096L LTC1098/LTC1098L U W U UO S I FOR ATIO reference voltage for a typical value of VOS. For example, a VOS of 2mV which is 0.1LSB with a 5V reference becomes 0.5LSB with a 1V reference and 2.5LSBs with a 0.2V reference. If this offset is unacceptable, it can be corrected digitally by the receiving system or by offsetting the “–” input of the LTC1096.
PAGE 22
LTC1096/LTC1096L LTC1098/LTC1098L U W U UO APPLICATI S I FOR ATIO 8 EFFECTIVE NUMBER OF BITS (ENOBs) Effective Number of Bits The effective number of bits (ENOBs) is a measurement of the resolution of an A/D and is directly related to the S/(N + D) by the equation: ENOB = [S/(N + D) –1.76]/6.02 where S/(N + D) is expressed in dB. At the maximum sampling rate of 33kHz the LTC1096 maintains 7.5 ENOBs or better to 40kHz.
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LTC1096/LTC1096L LTC1098/LTC1098L UO TYPICAL APPLICATI S Data Exchange Between LTC1098(L) and MC68HC05C4 START BIT MPU TRANSMIT WORD 0 0 0 1 BYTE 1 SGL/ ODD/ MSBF X DIFF SIGN BYTE 2 (DUMMY) X X X X X X X X X = DON'T CARE CS START SGL/ ODD/ DIFF SIGN MSBF DIN DON'T CARE CLK DOUT MPU RECEIVED WORD ? ? ? ? ? ? ? 0 B7 B6 B5 B4 B3 B2 B1 B0 B7 B6 B5 B4 B3 B2 B1 B0 1ST TRANSFER 2ND TRANSFER Hardware and Software Interface to Motorola MC68HC05C4 C0 CS ANALOG INPUT
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LTC1096/LTC1096L LTC1098/LTC1098L UO TYPICAL APPLICATI S Interfacing to the Parallel Port of the Intel 8051 Family LABEL The Intel 8051 has been chosen to demonstrate the interface between the LTC1098(L) and parallel port microprocessors. Normally the CS, CLK and DIN signals would be generated on three port lines and the DOUT signal read on a fourth port line. This works very well.
PAGE 25
LTC1096/LTC1096L LTC1098/LTC1098L UO TYPICAL APPLICATI S A “Quick Look” Circuit for the LTC1096 CS Users can get a quick look at the function and timing of the LT1096 by using the following simple circuit (Figure 13). VREF is tied to VCC. VIN is applied to the +IN input and the – IN input is tied to the ground. CS is driven at 1/16 the clock rate by the 74C161 and DOUT outputs the data.
PAGE 26
LTC1096/LTC1096L LTC1098/LTC1098L UO TYPICAL APPLICATI S Remote or Isolated Systems Figure 16 shows a floating system that sends data to a grounded host system. The floating circuitry is isolated by two optoisolators and powered by a simple capacitor diode charge pump. The system has very low power requirements because the LTC1096 shuts down between conversions and the optoisolators draw power only when data is being transferred.
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LTC1096/LTC1096L LTC1098/LTC1098L U PACKAGE DESCRIPTIO Dimensions in inches (millimeters), unless otherwise noted. N8 Package 8-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.400* (10.160) MAX 8 7 6 5 1 2 3 4 0.255 ± 0.015* *THESE DIMENSIONS DO NOT INCLUDE (6.477 ± 0.381) MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm) 0.300 – 0.325 (7.620 – 8.255) 0.065 (1.651) TYP 0.009 – 0.015 (0.229 – 0.381) ( +0.635 –0.381 0.125 (3.175) MIN 0.005 (0.
PAGE 28
LTC1096/LTC1096L LTC1098/LTC1098L UO TYPICAL APPLICATI A/D Conversion for 3V Systems The LTC1096/LTC1098 are ideal for 3V systems. Figure 17 shows a 3V to 6V battery current monitor that draws only 70µA from the battery it monitors. The battery current is sensed with the 0.02Ω resistor and amplified by the LT1178. The LTC1096 digitizes the amplifier output and sends it to the microprocessor in serial format. The LT1004 provides the full-scale reference for the ADC.