Linear Technology LTC1286IS8, LTC1286CN8, LTC1286, LTC1298IN8, LTC1298CS8 Datasheet

FEATURES

■12-Bit Resolution

■8-Pin SOIC Plastic Package

■Low Cost

■Low Supply Current: 250μA Typ.

■Auto Shutdown to 1nA Typ.

■Guaranteed ±3/4LSB Max DNL

■Single Supply 5V to 9V Operation

■On-Chip Sample-and-Hold

■60μs Conversion Time

■Sampling Rates:

12.5ksps (LTC1286)

11.1ksps (LTC1298)

■I/O Compatible with SPI, Microwire, etc.

■Differential Inputs (LTC1286)

■2-Channel MUX (LTC1298)

■3V Versions Available: LTC1285/LTC1288

APPLICATIOUS

■Battery-Operated Systems

■Remote Data Acquisition

■Battery Monitoring

■Handheld Terminal Interface

■Temperature Measurement

■Isolated Data Acquisition

LTC1286/LTC1298

Micropower Sampling

12-Bit A/D Converters In

S0-8 Packages

DESCRIPTIOU

The LTC1286/LTC1298 are micropower, 12-bit, successive approximation sampling A/D converters. They typically draw only 250μA of supply current when converting and automatically power down to a typical supply current of 1nA whenever they are not performing conversions. They are packaged in 8-pin SO packages and operate on 5V to 9V supplies. These 12-bit, switched-capacitor, successive approximation ADCs include sample-and-holds. The LTC1286 has a single differential analog input. The LTC1298 offers 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 (to 1.5V full scale) allow direct connection to sensors and transducers in many applications, eliminating the need for gain stages.

TYPICAL APPLICATIO

U

S

25μW, S0-8 Package, 12-Bit ADC

Supply Current vs Sample Rate

Samples at 200Hz and Runs Off a 5V Supply

1000

TA = 25°C

4.7μF

5V

VCC = VREF = 5V

(μA)

fCLK = 200kHz

100

CURRENT

MPU

1

8

(e.g., 8051)

ANALOG INPUT

+IN

LTC1286

CLK

P1.3

SUPPLY

10

2

7

VREF

VCC

P1.4

0V TO 5V RANGE

3

–IN

DOUT

6

P1.2

4

5

SERIAL DATA LINK

GND

CS/SHDN

LTC1286/98 • TA01

1

1k

10k

100k

0.1k

SAMPLE FREQUENCY (Hz)

LTC1286/98 • TA02

1

LTC1286/LTC1298

ABSOLUTE

WAXIWUW

RATINGS (Notes 1 and 2)

Supply Voltage (VCC) to GND	................................... 12V
Voltage
Analog and Reference ................	– 0.3V to V CC + 0.3V
Digital Inputs.........................................	–0.3V to 12V
Digital Output .............................	– 0.3V to V CC + 0.3V

Power Dissipation ..............................................	500mW
Operating Temperature Range	0°C to 70°C
LTC1286C/LTC1298C.............................
LTC1286I/LTC1298I ...........................	–40°C to 85°C
Storage Temperature Range .................	– 65°C to 150°C
Lead Temperature (Soldering, 10 sec.)................	300°C

PACKAGE/ORDER I

U

FORWATIOU

TOP VIEW

ORDER PART

TOP VIEW

ORDER PART

VCC

NUMBER

VREF

VCC

NUMBER

VREF

1

8

1

8

CLK

+IN

+IN

2

7

LTC1286CN8

2

7

CLK

LTC1286CS8

DOUT

–IN

3

6

–IN

3

6

DOUT

GND

LTC1286IN8

LTC1286IS8

4

5

CS/SHDN

GND

4

5

CS/SHDN

PART MARKING

N8 PACKAGE

S8 PACKAGE

8-LEAD PLASTIC DIP

8-LEAD PLASTIC SOIC

1286C

TJMAX = 150°C, θJA = 130°C/W

TJMAX = 150°C, θJA = 175°C/W

1286I

TOP VIEW

ORDER PART

TOP VIEW

ORDER PART

VCC (VREF)

NUMBER

VCC (VREF)

NUMBER

CS/SHDN

1

8

CS/SHDN

1

8

CLK

CH0

2

7

LTC1298CN8

CH0

2

7

CLK

LTC1298CS8

DOUT

CH1

3

6

LTC1298IN8

CH1

3

6

DOUT

LTC1298IS8

DIN

GND

4

5

GND

4

5

DIN

PART MARKING

N8 PACKAGE

S8 PACKAGE

8-LEAD PLASTIC DIP

8-LEAD PLASTIC SOIC

1298C

TJMAX = 150°C, θJA = 130°C/W

TJMAX = 150°C, θJA = 175°C/W

1298I

Consult factory for military grade parts.

RECOWWE

U

DED OPERATI

U

G CO

U

DITIO

U

S

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

VCC

Supply Voltage (Note 3)

LTC1286

4.5

9.0

V

LTC1298

4.5

5.5

V

fCLK

Clock Frequency

VCC = 5V

(Note 4)

200

kHz

tCYC

Total Cycle Time

LTC1286, fCLK = 200kHz

80

μs

LTC1298, fCLK = 200kHz

90

μs

thDI

Hold Time, DIN After CLK−

VCC = 5V

150

ns

tsuCS

Setup Time

↓ Before First CLK− (See Operating Sequence)

LTC1286, VCC = 5V

2

μs

CS

LTC1298, VCC = 5V

2

μs

tsuDI

Setup Time, DIN Stable Before CLK−

VCC = 5V

400

ns

tWHCLK

CLK High Time

VCC = 5V

2

μs

tWLCLK

CLK Low Time

VCC = 5V

2

μs

tWHCS

High Time Between Data Transfer Cycles

VCC = 5V

2

μs

CS

tWLCS

Low Time During Data Transfer

LTC1286, fCLK = 200kHz

75

μs

CS

LTC1298, fCLK = 200kHz

85

μs

2

LTC1286/LTC1298

CO

U

VERTER A

U

D

WULTIPLEXER CHARACTERISTICS (Note 5)

				LTC1286			LTC1298
PARAMETER	CONDITIONS		MIN	TYP	MAX	MIN	TYP	MAX	UNITS
Resolution (No Missing Codes)		●	12			12			Bits
Integral Linearity Error	(Note 6)	●		±3/4	±2		±3/4	±2	LSB
Differential Linearity Error		●		±1/4	±3/4		±1/4	±3/4	LSB
Offset Error		●		3/4	±3		3/4	±3	LSB
Gain Error		●		±2	±8		±2	±8	LSB
Analog Input Range	(Note 7 and 8)	●			–0.05V to V	CC + 0.05V			V
REF Input Range (LTC1286)	4.5 £ VCC £ 5.5V				1.5V to VCC + 0.05V				V
(Notes 7, 8, and 9)	5.5V < VCC £ 9V				1.5V to 5.55V				V
Analog Input Leakage Current (Note 10)		●			±1			±1	mA

DIGITAL A

U

D DC ELECTRICAL CHARACTERISTICS

(Note 5)

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

VIH

High Level Input Voltage

VCC = 5.25V

●

2

V

VIL

Low Level Input Voltage

VCC = 4.75V

●

0.8

V

IIH

High Level Input Current

VIN = VCC

●

2.5

mA

IIL

Low Level Input Current

VIN = 0V

●

– 2.5

mA

VOH

High Level Output Voltage

VCC = 4.75V, IO = 10mA

●

4.0

4.64

V

VCC = 4.75V, IO = 360mA

●

2.4

4.62

V

VOL

Low Level Output Voltage

VCC = 4.75V, IO = 1.6mA

●

0.4

V

IOZ

Hi-Z Output Leakage

±3

mA

CS

= High

●

ISOURCE

Output Source Current

VOUT = 0V

– 25

mA

ISINK

Output Sink Current

VOUT = VCC

45

mA

RREF

Reference Input Resistance

5000

MW

CS

= VCC

(LTC1286)

CS = GND

55

kW

IREF

Reference Current (LTC1286)

= VCC

0.001

2.5

mA

CS

●

tCYC ³ 640ms, fCLK £ 25kHz

●

90

140

mA

tCYC = 80ms, fCLK = 200kHz

●

90

140

mA

ICC

Supply Current

= VCC

0.001

±3.0

mA

CS

●

LTC1286, tCYC ³ 640ms, fCLK £ 25kHz

●

200

400

mA

LTC1286, tCYC = 80ms, fCLK = 200kHz

●

250

500

mA

LTC1298, tCYC ³ 720ms, fCLK £ 25kHz

●

290

490

mA

LTC1298, tCYC = 90ms, fCLK = 200kHz

●

340

640

mA

DY

U

AWIC ACCURACY

fSMPL = 12.5kHz (LTC1286), fSMPL = 11.1kHz (LTC1298) (Note 5)

SYMBOL	PARAMETER	CONDITIONS	MIN	TYP	MAX	UNITS
S/(N +D)	Signal-to-Noise Plus Distortion Ratio	1kHz/7kHz Input Signal		71/68		dB
THD	Total Harmonic Distortion (Up to 5th Harmonic)	1kHz/7kHz Input Signal		– 84/–80		dB
SFDR	Spurious-Free Dynamic Range	1kHz/7kHz Input Signal		90/86		dB
	Peak Harmonic or Spurious Noise	1kHz/7kHz Input Signal		– 90/–86		dB

3

LTC1286/LTC1298

AC CHARACTERISTICS (Note 5)

SYMBOL	PARAMETER			CONDITIONS		MIN	TYP	MAX	UNITS
tSMPL	Analog Input Sample Time			See Operating Sequence			1.5		CLK Cycles
fSMPL (MAX)	Maximum Sampling Frequency			LTC1286	●	12.5			kHz
				LTC1298	●	11.1			kHz
tCONV	Conversion Time			See Operating Sequence			12		CLK Cycles
tdDO	Delay Time, CLK¯ to DOUT Data Valid			See Test Circuits	●		250	600	ns
tdis	Delay Time,		- to DOUT Hi-Z	See Test Circuits			135	300	ns
		CS			●
ten	Delay Time, CLK¯ to DOUT Enable			See Test Circuits	●		75	200	ns
thDO	Time Output Data Remains Valid After CLK¯			CLOAD = 100pF			230		ns
tf	DOUT Fall Time			See Test Circuits	●		20	75	ns
tr	DOUT Rise Time			See Test Circuits	●		20	75	ns
CIN	Input Capacitance			Analog Inputs, On Channel			20		pF
				Analog Inputs, Off Channel			5		pF
				Digital Input			5		pF

The ● denotes specifications which apply over the full operating temperature range.

Note 1: Absolute maximum ratings are those values beyond which the life of a device may be impaired.

Note 2: All voltage values are with respect to GND.

Note 3: These devices are specified at 5V. For 3V specified devices, see LTC1285 and LTC1288.

Note 4: Increased leakage currents at elevated temperatures cause the S/H to droop, therefore it is recommended that fCLK ³ 120kHz at 85°C, fCLK ³ 75kHz at 70° and fCLK ³ 1kHz at 25°C.

Note 5: VCC = 5V, VREF = 5V and CLK = 200kHz unless otherwise specified.

Note 6: Linearity error is specified between the actual end points of the A/D transfer curve.

Note 7: Two on-chip diodes are tied to each reference and analog input which will conduct for reference or analog input voltages one diode drop below GND or one diode drop above VCC. This spec allows 50mV forward bias of either diode for 4.5V £ VCC £ 5.5V. This means that as long as the reference or analog input does not exceed the supply voltage by more than 50mV the output code will be correct. To achieve an absolute 0V to 5V input voltage range will therefore require a minimum supply voltage of 4.950V over initial tolerance, temperature variations and loading. For 5.5V < VCC £ 9V, reference and analog input range cannot exceed 5.55V. If reference and analog input range are greater than 5.55V, the output code will not be guaranteed to be correct.

Note 8: The supply voltage range for the LTC1286 is from 4.5V to 9V, but the supply voltage range for the LTC1298 is only from 4.5V to 5.5V.

Note 9: Recommended operating conditions

Note 10: Channel leakage current is measured after the channel selection.

TYPICAL PERFORWAUCE CHARACTERISTICS

Supply Current vs Sample Rate

1000		TA = 25°C
		VCC = VREF = 5V
(µA)		fCLK = 200kHz
CURRENT	100
		LTC1298
SUPPLY		LTC1286
	10
	1

0.1k 1k 10k 100k SAMPLE RATE (kHz)

LT1286/98 G03

Supply Current vs Temperature

450

TA = 25°C

400

VCC = VREF = 5V

(µA)

fCLK = 200kHz

CURRENT

350

LTC1298 fSMPL =11.1kHz

SUPPLY

300

250

LTC1286 fSMPL =12.5kHz

200 –55 –35 –15 5 25 45 65 85 105 125

TEMPERATURE (°C)

LT1286/98 G04

Shutdown Supply Current vs Clock Rate with CS High and CS Low

	35
		TA = 25°C
	30
(µA)		VCC = VREF			= 5V
	25
CURRENT
	20
	15
										= 0
SUPPLY								CS
	5
	10						(AFTER CONVERSION)
	1
0.002
						= VCC
				CS

0 1 20 40 60 80 100 120 140 160 180 200

FREQUENCY (kHz)

LT1286/98 G01

4

LTC1286/LTC1298

TYPICAL PERFORWA

U

CE CHARACTERISTICS

Reference Current vs

Sample Rate (LTC1286)

	100	TA = 25°C
	90
		VCC = 5V
μA)	80	VREF = 5V
	70	fCLK = 200kHz
(
CURRENT
	60
	50
REFERENCE	40
	30
	20
	10
	0		4	6	8	10		14
	0	2					12

FREQUENCY (kHz)

LT1286/98 G06

Change in Offset vs Temperature

	0
(LSB)	-0.5
	-1
OFFSET
	1.5
IN
CHANGE	-2
	-2.5				VCC = VREF = 5V
					fCLK = 200kHz
					fSMPL = fSMPL (MAX)
	-3
					-35 -15			5		25			45			65 85
	-55
							TEMPERATURE (°C)
																LT1286/98 G09
		Peak-to-Peak ADC Noise vs
		Reference Voltage
	2
					TA = 25°C
					VCC = 5V
	1.5				fCLK = 200kHz
IN LBSs
NOISEADC	1
	0.5
	0
					2					3			4			5
	1

REFERENCE VOLTAGE (V)

LT1286/98 G15

	Change in Offset vs
Reference Current vs Temperature	Reference Voltage

	95	VCC = VREF = 5V										3					TA = 25°C
											)
	94.5	fSMPL = 12.5kHz									REF	2.5					VCC = 5V
		fCLK	= 200kHz								V						fCLK = 200kHz
(µA)CURRENTREFERENCE											1/4096=(LSBOFFSETINCHANGE
		TA = 25°C															fSMPL = 12.5kHz
	94											2
	93.5											1.5
	93											1
	92.5											0.5
	92		–15			45		85		125		0	1.5	2	2.5	3	3.5	4	4.5	5
	–55 –35			5	25		65		105			1

								TEMPERATURE (°C)																						REFERENCE VOLTAGE (V)
																		LT1286/98 G07																												LT1286/98 G08
	Change In Linearity vs																									Change In Gain vs
	Reference Voltage																									Reference Voltage
	–0.5																								–10
	–0.45												TA = 25°C												–9															TA = 25°C
													VCC = 5V																											VCC = 5V
(LSB)LINEARITY	–0.4												fCLK = 200kHz												–8															fCLK = 200kHz
	–0.35												fSMPL = 12.5kHz											(LSB)GAININ	–7															fSMPL = 12.5kHz
	–0.3																								–6
INCHANGE	–.25																							CHANGE	–5
	–0.2																								–4
	–0.15																								–3
	–0.1																								–2
	–0.05																								–1
	0 1																								0 1
			1.5			2		2.5		3			3.5			4		4.5			5						1.5			2		2.5				3			3.5				4			4.5		5
						REFERENCE VOLTAGE (V)																								REFERENCE VOLTAGE (V)
																		LT1286/98 G10																												LT1286/98 G11
			Differential Nonlinearity vs Code																							Effective Bits and S/(N + D)
																										vs Input Frequency
NONLINEARITYDIFFERENTIALERROR (LBS)	1.0																								12																										74
	0.80																							NUMBEREFFECTIVEOF BITS (ENOBs)	11																										68
																											fSMPL =				12.5kHz
																									1																										62
	0.60																								10
	0.40																								9																										56
	0.20																								8																										50
	0.00																								7																										44
																									6																										38
	–0.20																								5
	–0.40																								4
	–0.60																								3		TA = 25°C
																									2		VCC = 5V
	–0.80																										fCLK = 200kHz
	–1.0																								0
			0							2048											4096
																																10							100									1000
																									1

CODE

INPUT FREQUENCY (kHz)

LTC 1286/98 G20

5

LTC1286/LTC1298

TYPICAL PERFORWAUCE CHARACTERISTICS

		Spurious Free Dynamic Range
		vs Frequency																												S/(N+D) vs Input Level
	100																												80
RANGEDYNAMIC(dB)	90																											DISTORTIONPLUS(dB)	70			TA = 25°C
																																VCC = VREF = 5V
	80																															fIN = 1kHz
	70																												60			fSMPL = 12.5kHz
																													50
	60
FREESPURIOUS	50																												40
	40																											NOISE-TO-SIGNAL
																													30
	30
																													20
	20
			TA = 25°C
	10		VCC = VREF = 5V																										10
			fSMPL = 12.5kHz
	0																												0
									10k								100k								1M
	1k																																–30		–20		–10		0
																													–40
							INPUT FREQUENCY (Hz)
																																		INPUT LEVEL			(dB)

LTC 1286/98 G27

LT1286/98 G25

4096 Point FFT Plot

	0
			TA = 25°C
	–20		VCC = VREF = 5V
			fIN = 5kHz
	–40		fCLK = 200kHz
(dB)			fSMPL = 12.5kHz
MAGNITUDE	–60
	–80

–100

–120

–140

0 1 2 3 4 5 6 7 FREQUENCY (kHz)

LTC 1286/98 G21

	Maximum Clock Frequency vs
	Source Resistance
	300
(kHz)	250
	200
FREQUENCY
														–INPUT
CLOCK	150												VIN	+INPUT
	100
														RSOURCE–
	50
			TA = 25°C
	0		VCC = VREF = 5V
												1		10
	0.1
				SOURCE RESISTANCE (kΩ)

LT1286/98 G12

	Intermodulation Distortion
	0	TA = 25°C
	–20	VCC = VREF = 5V
		f1 = 5kHz
	–40	f2 = 6kHz
(dB)		fSMPL = 12.5kHz
	–60
MAGNITUDE
	–80
	–100
	–120
	–140				4		6	7
	0	1	2	3		5
			FREQUENCY (kHz)
							LTC 1286/98 G24
	Sample and Hold Aquisition
	Time vs Source Resistance
10000
		TA = 25°C
TIME (ns)		VCC = VREF = 5V
ACQUISITION	1000					RSOURCE+
S&H					VIN		+INPUT
							–INPUT

100

0.1 1 10 100 1000 10000 SOURCE RESISTANCE (Ω)

LT1286/98 G16

Attenuation vs

Input Frequency

	0
	10
	20
(%)	30
	40
ATTENUATION
	50
	60
	70
	80		TA =		25°C

90VCC = VREF = 5V fSMPL = 12.5kHz

100

1 10k 100k 1M 10M INPUT FREQUENCY (Hz)

LTC 1286/98 G26

Power Supply Feedthrough vs Ripple Frequency

	0	TA = 25°C
		VCC = 5V (VRIPPLE = 20mV)
		VREF = 5V
(dB)		fCLK = 200kHz
FEEDTHROUGH	–50
–100		10
	1		100	1000	10000

RIPPLE FREQUENCY (kHz)

LTC 1286/98 G22

Maximum Clock Frequency vs

Supply Voltage

	300	TA = 25°C
	290	VCC = VREF = 5V
(kHz)
FREQUENCY	280
	270
CLOCK
	260
	250	6	7	8
	5				9

SUPPLY VOLTAGE (V)

LT1286/98 G13

6

DOUT

DOUT

TYPICAL PERFORWAUCE CHARACTERISTICS

Minimum Clock Frequency

Digital Input Logic Threshold

for 0.1 LSB Error vs Temperature

vs Supply Voltage

200

(V)

3

VCC = VREF = 5V

TA = 25°C

(kHz)

150

VOLTAGE

FREQUENCY

THRESHOLD

2

100

CLOCK

LOGICDIGITAL

50

1

0

–55 –35 –15	5	25	45	65 85	3	4	5	6	7	8	9
TEMPERATURE (°C)							SUPPLY VOLTAGE (V)
				LT1286/98 • G14						LTC 1286/98 G17

LTC1286/LTC1298

Input Channel Leakage Current vs Temperature

	1000
			VCC = 5V
	100		VREF = 5V
(nA)
CURRENT	10							ON	CHANNEL
LEAKAGE	1											OFF			CHANNEL
	0.1
	0.01
						0										100 120 140
	– 60 –40 –20							20		40		60		80

TEMPERATURE (°C)

1196/98 G19

PIU FUUCTIOUS

LTC1286

VREF (Pin 1): Reference Input. The reference input defines the span of the A/D converter.

IN+ (Pin 2): Positive Analog Input.

IN– (Pin 3): Negative Analog Input.

GND (Pin 4): Analog Ground. GND should be tied directly to an analog ground plane.

CS/SHDN (Pin 5): Chip Select Input. A logic low on this input enables the LTC1286. A logic high on this input disables and powers down the LTC1286.

(Pin 6): Digital Data Output. The A/D conversion result is shifted out of this output.

CLK (Pin 7): Shift Clock. This clock synchronizes the serial data transfer and determines conversion speed.

VCC (Pin 8): Power Supply Voltage. This pin provides power to the A/D converter. It must be kept free of noise and ripple by bypassing directly to the analog ground plane.

LTC1298

CS/SHDN (Pin 1): Chip Select Input. A logic low on this input enables the LTC1298. A logic high on this input disables and powers down the LTC1298.

CH0 (Pin 2): Analog Input.

CH1 (Pin 3): Analog Input.

GND (Pin 4): Analog Ground. GND should be tied directly to an analog ground plane.

DIN (Pin 5): Digital Data Input. The multiplexer address is shifted into this input.

(Pin 6): Digital Data Output. The A/D conversion result is shifted out of this output.

CLK (Pin 7): Shift Clock. This clock synchronizes the serial data transfer and determines conversion speed.

VCC/VREF (Pin 8): Power Supply and Reference Voltage. This pin provides power and defines the span of the A/D converter. It must be kept free of noise and ripple by bypassing directly to the analog ground plane.

7

LTC1286/LTC1298

BLOCK DIAGRAW

					CS/SHDN
VCC (VCC/VREF)				(DIN)				CLK

IN+ (CH0)

IN– (CH1)

BIAS AND		SERIAL PORT	DOUT
SHUTDOWN CIRCUIT
CSAMPLE
–
		SAR
+	MICROPOWER
	COMPARATOR
	CAPACITIVE DAC

GND	VREF	PIN NAMES IN PARENTHESES
		REFER TO THE LTC1298

TEST CIRCUITS

Load Circuit for tdDO, tr and tf

1.4V

3k

DOUT

100pF

TEST POINT

LTC1286/98 • TC01

Voltage Waveforms for DOUT Rise and Fall Times, tr, tf

VOH

DOUT

VOL

tr								tf	LTC1286/98 • TC02

Voltage Waveforms for DOUT Delay Times, tdDO

Load Circuit for tdis and ten

CLK

TEST POINT

VIL

VCC tdis WAVEFORM 2, ten

tdDO

VOH

DOUT

3k

tdis WAVEFORM 1

DOUT

100pF

VOL

LTC1286/98 • TC03

LTC1286/98 • TC04

8