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LTC1196/LTC1198

119698fb

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

8-Bit, SO-8, 1Msps ADCs

with Auto-Shutdown Options

Single 5V Supply, 1Msps, 8-Bit Sampling ADC

High Speed Data Acquisition

Disk Drives

Portable or Compact Instrumentation

Low Power or Battery-Operated Systems

High Sampling Rates: 1MHz (LTC1196)

750kHz (LTC1198)

Low Cost

Single Supply 3V and 5V Speciﬁ cations

Low Power: 10mW at 3V Supply

50mW at 5V Supply

Auto-Shutdown: 1nA Typical (LTC1198)

±1/2LSB Total Unadjusted Error over Temperature

3-Wire Serial I/O

1V to 5V Input Span Range (LTC1196)

Converts 1MHz Inputs to 7 Effective Bits

Differential Inputs (LTC1196)

2-Channel MUX (LTC1198)

SO-8 Plastic Package

The LTC

1196/LTC1198 are 600ns, 8-bit A/D converters

with sampling rates up to 1MHz. They are offered in 8-pin

SO packages and operate on 3V to 6V supplies. Power

dissipation is only 10mW with a 3V supply or 50mW with

a 5V supply. The LTC1198 automatically powers down

to a typical supply current of 1nA whenever it is not

performing conversions. These 8-bit switched-capacitor

successive approximation ADCs include sample-and-

holds. The LTC1196 has a differential analog input; the

LTC1198 offers a software selectable 2-channel MUX.

The 3-wire serial I/O, SO-8 packages, 3V operation and

extremely high sample rate-to-power ratio make these

ADCs an ideal choice for compact, high speed systems.

These ADCs can be used in ratiometric applications or

with external references. The high impedance analog in-

puts and the ability to operate with reduced spans below

1V full scale (LTC1196) allow direct connection to signal

sources in many applications, eliminating the need for

gain stages.

The A-grade devices are speciﬁ ed with total unadjusted

error of ±1/2LSB maximum over temperature.

Effective Bits and S/(N + D) vs Input Frequency

INPUT FREQUENCY (Hz)

S/(N + D) (dB)

10k 100k 1M

11968 TA01b

EFFECTIVE NUMBER OF BITS (ENOBs)

REF

= 2.7V

SMPL

= 383kHz (LTC1196)

SMPL

= 287kHz (LTC1198)

REF

= 5V

SMPL

= 1MHz (LTC1196)

SMPL

= 750kHz (LTC1198)

= 25°C

5V1μF

ANALOG INPUT

0V TO 5V RANGE

1196/98 TA01

SERIAL DATA LINK TO

ASIC, PLD, MPU, DSP,

OR SHIFT REGISTERS

–IN

GND

CLK

OUT

+IN

LTC1196

REF

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

Summary of content (28 pages)

PAGE 1
LTC1196/LTC1198 8-Bit, SO-8, 1Msps ADCs with Auto-Shutdown Options FEATURES n n n n n n n n n n n n DESCRIPTION High Sampling Rates: 1MHz (LTC1196) 750kHz (LTC1198) Low Cost Single Supply 3V and 5V Speciﬁcations Low Power: 10mW at 3V Supply 50mW at 5V Supply Auto-Shutdown: 1nA Typical (LTC1198) ±1/2LSB Total Unadjusted Error over Temperature 3-Wire Serial I/O 1V to 5V Input Span Range (LTC1196) Converts 1MHz Inputs to 7 Effective Bits Differential Inputs (LTC1196) 2-Channel MUX (LTC1198) SO-8 Plastic Pack
PAGE 2
LTC1196/LTC1198 ABSOLUTE MAXIMUM RATINGS (Notes 1, 2) Supply Voltage (VCC) to GND .................................... 7V Voltage Analog Reference ....................... –0.3V to VCC + 0.3V Digital Inputs ......................................... –0.3V to 7V Digital Outputs ........................... –0.3V to VCC + 0.3V Power Dissipation ..............................................
PAGE 3
LTC1196/LTC1198 RECOMMENDED OPERATING CONDITIONS The l denotes the speciﬁcations which apply over SYMBOL PARAMETER LTC1196-1 LTC1198-1 TYP VCC Supply Voltage the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. CONDITIONS MIN LTC1196-2 LTC1198-2 TYP MAX MAX MIN 2.7 6 2.7 6 0.01 0.01 14.4 12.0 0.01 0.01 12.0 9.
PAGE 4
LTC1196/LTC1198 DIGITAL AND DC ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VCC = 5V, VREF = 5V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS VOL Low Level Output Voltage VCC = 4.75V, IO = 1.6mA l l IOZ Hi-Z Output Leakage CS = HIGH ISOURCE Output Source Current VOUT = 0V MIN TYP MAX UNITS 0.
PAGE 5
LTC1196/LTC1198 RECOMMENDED OPERATING CONDITIONS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VCC = 2.7V operation. SYMBOL PARAMETER fCLK Clock Frequency tCYC Total Cycle Time CONDITIONS MIN l LTC1196 LTC1198 LTC1196-1 LTC1198-1 TYP 0.01 0.01 MAX MIN 5.4 4.6 0.01 0.01 LTC1196-2 LTC1198-2 TYP MAX UNITS 4 3 MHz MHz 12 16 12 16 CLK CLK tSMPL Analog Input Sampling Time 2.5 2.
PAGE 6
LTC1196/LTC1198 DIGITAL AND DC ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VCC = 2.7V, VREF = 2.5V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS ISOURCE Output Source Current VOUT = 0V ISINK Output Sink Current VOUT = VCC MIN IREF Reference Current, LTC1196 CS = VCC fSMPL = fSMPL(MAX) l l ICC Supply Current CS = VCC = 3.3V, LTC1198 (Shutdown) CS = VCC = 3.
PAGE 7
LTC1196/LTC1198 ELECTRICAL CHARACTERISTICS Note 4: Total unadjusted error includes offset, full scale, linearity, multiplexer and hold step errors. Note 5: Channel leakage current is measured after the channel selection. Note 2: All voltage values are with respect to GND. Note 3: Integral nonlinearity is deﬁned as deviation of a code from a straight line passing through the actual endpoints of the transfer curve. The deviation is measured from the center of the quantization band.
PAGE 8
LTC1196/LTC1198 TYPICAL PERFORMANCE CHARACTERISTICS Linearity Error vs Reference Voltage 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 –0.1 –0.2 0.2 –0.3 0.1 –0.4 2.5 0.2 0.1 0 –0.1 –0.2 –0.3 –0.4 –0.5 5.5 17 6.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) 5.5 –0.2 –0.3 –0.5 6.0 18 7 14 12 70 60 50 40 30 20 10 5 25 45 65 85 105 125 TEMPERATURE (°C) 1196/98 G13 VIN +IN 10 –IN 8 RSOURCE– 6 4 2 5.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 3.0 5.5 0 6.
PAGE 9
LTC1196/LTC1198 TYPICAL PERFORMANCE CHARACTERISTICS Digital Input Logic Threshold vs Supply Voltage 1.9 DOUT Delay Time vs Supply Voltage TA = 25°C 1.5 1.3 1.1 0.9 100 80 60 40 0.5 2.5 5.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 3.0 5.5 3.0 5.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) Input Channel Leakage Current vs Temperature 40 ON CHANNEL 1 OFF CHANNEL 0.1 0 0 32 64 96 128 160 192 224 256 CODE 0.5 –0.
PAGE 10
LTC1196/LTC1198 TYPICAL PERFORMANCE CHARACTERISTICS 4096 Point FFT Plot at 5V –20 –40 –50 –60 –70 –20 –30 –40 –50 –60 –70 –30 –40 –50 –60 –70 –80 –90 –90 –90 300 200 FREQUENCY (kHz) 400 –100 500 0 50 150 100 FREQUENCY (kHz) –20 –30 –40 –50 –60 –60 –70 –70 10k 100k RIPPLE FREQUENCY (Hz) 1k 1M 10k 100k RIPPLE FREQUENCY (Hz) Intermodulation Distortion at 2.
PAGE 11
LTC1196/LTC1198 TYPICAL PERFORMANCE CHARACTERISTICS Output Amplitude vs Input Frequency Spurious-Free Dynamic Range vs Frequency 70 SPURIOUS-FREE DYNAMIC RANGE (dB) PEAK-TO-PEAK OUTPUT (%) 100 80 VREF = VCC = 5V 60 VREF = VCC = 2.7V 40 20 0 50 100k 10k 1M INPUT FREQUENCY (Hz) VCC = 3V fCLK = 5MHz 40 30 20 10 0 1k VCC = 5V fCLK = 12MHz 60 TA = 25°C 1k 10M 10k 100k 1M 10M FREQUENCY (Hz) 1196/98 G35 1196/98 G34 PIN FUNCTIONS LTC1196 LTC1198 CS (Pin 1): Chip Select Input.
PAGE 12
LTC1196/LTC1198 BLOCK DIAGRAM CS (CS/SHUTDOWN) CLK VCC (VCC/VREF) BIAS AND SHUTDOWN CIRCUIT IN+ (CH0) CSMPL SERIAL PORT DOUT – IN– (CH1) + SAR HIGH SPEED COMPARATOR CAPACITIVE DAC 1196/98 BD PIN NAMES IN PARENTHESES REFER TO THE LTC1198 GND VREF (DIN) TEST CIRCUITS On and Off Channel Leakage Current Load Circuit for tdDO, tr and tf 5V 1.
PAGE 13
LTC1196/LTC1198 TEST CIRCUITS Load Circuit for tdis and ten Voltage Waveforms for tdis TEST POINT VIH CS VCC tdis WAVEFORM 2, ten 3k DOUT DOUT WAVEFORM 1 (SEE NOTE 1) tdis WAVEFORM 1 20pF 90% tdis 1196/98 TC05 DOUT WAVEFORM 2 (SEE NOTE 2) 10% NOTE 1: WAVEFORM 1 IS FOR AN OUTPUT WITH INTERNAL CONDITIONS SUCH THAT THE OUTPUT IS HIGH UNLESS DISABLED BY THE OUTPUT CONTROL. NOTE 2: WAVEFORM 2 IS FOR AN OUTPUT WITH INTERNAL CONDITIONS SUCH THAT THE OUTPUT IS LOW UNLESS DISABLED BY THE OUTPUT CONTROL.
PAGE 14
LTC1196/LTC1198 APPLICATIONS INFORMATION OVERVIEW can convert either channel with respect to ground or the difference between the two. It also automatically powers down when not performing conversion, drawing only leakage current. The LTC1196/LTC1198 are 600ns sampling 8-bit A/D converters packaged in tiny 8-pin SO packages and operating on 3V to 6V supplies. The ADCs draw only 10mW from a 3V supply or 50mW from a 5V supply.
PAGE 15
LTC1196/LTC1198 APPLICATIONS INFORMATION Connection to a microprocessor or a DSP serial port is quite simple (see the Data Transfer section). It requires no additional hardware, but the speed will be limited by the clock rate of the microprocessor or the DSP which limits the conversion time of the LTC1196/LTC1198. two null bits and the conversion result are output on the DOUT line. At the end of the data exchange CS should be brought HIGH. This resets the LTC1198 in preparation for the next data exchange.
PAGE 16
LTC1196/LTC1198 APPLICATIONS INFORMATION Dummy Bits Unipolar Transfer Curve The last two bits of the input word following the MUX address are dummy bits. Either bit can be a logical one or a logical zero. These two bits allow the ADC 2.5 clocks to acquire the input signal after the channel selection. The LTC1196/LTC1198 are permanently conﬁgured for unipolar only. The input span and code assignment for this conversion type are shown in the following ﬁgures.
PAGE 17
LTC1196/LTC1198 APPLICATIONS INFORMATION REDUCING POWER CONSUMPTION The LTC1196/LTC1198 can sample at up to a 1MHz rate, drawing only 50mW from a 5V supply. Power consumption can be reduced in two ways. Using a 3V supply lowers the power consumption on both devices by a factor of ﬁve, to 10mW. The LTC1198 can reduce power even further because it shuts down whenever it is not converting. Figure 5 shows the supply current versus sample rate for the LTC1196 and LTC1198 on 3V and 5V.
PAGE 18
LTC1196/LTC1198 APPLICATIONS INFORMATION Mixed Supplies BOARD LAYOUT CONSIDERATIONS It is possible to have a digital system running off a 5V supply and communicate with the LTC1196/LTC1198 operating on a 3V supply. Achieving this reduces the outputs of DOUT from the ADCs to toggle the equivalent input of the digital system.
PAGE 19
LTC1196/LTC1198 APPLICATIONS INFORMATION Single-Ended Inputs “+” Input Settling The sample-and-hold of the LTC1198 allows conversion of rapidly varying signals. The input voltage is sampled during the tSMPL time as shown in Figure 7. The sampling interval begins as the bit preceding the ﬁrst dummy bit is shifted in and continues until the falling CLK edge after the second dummy bit is received. On this falling edge, the S&H goes into hold mode and the conversion begins.
PAGE 20
LTC1196/LTC1198 APPLICATIONS INFORMATION Source Resistance Reduced Reference Operation The analog inputs of the LTC1196/LTC1198 look like a 25pF capacitor (CIN) in series with a 120Ω resistor (RON) as shown in Figure 8. CIN gets switched between the selected “+” and “–” inputs once during each conversion cycle. Large external source resistors will slow the settling of the inputs.
PAGE 21
LTC1196/LTC1198 APPLICATIONS INFORMATION Noise with Reduced VREF DYNAMIC PERFORMANCE The total input referred noise of the LTC1196 can be reduced to approximately 2mVP-P using a ground plane, good bypassing, good layout techniques and minimizing noise on the reference inputs. This noise is insigniﬁcant with a 5V reference but will become a larger fraction of an LSB as the size of the LSB is reduced. The LTC1196/LTC1198 have exceptionally high speed sampling capability.
PAGE 22
LTC1196/LTC1198 APPLICATIONS INFORMATION where N is the effective number of bits of resolution and S/(N + D) is expressed in dB. At the maximum sampling rate of 1.2MHz with a 5V supply the LTC1196 maintains above 7.5 ENOBs at 400kHz input frequency. Above 500kHz the ENOBs gradually decline, as shown in Figure 11, due to increasing second harmonic distortion. The noise ﬂoor remains low. 50 VREF = VCC = 2.
PAGE 23
LTC1196/LTC1198 APPLICATIONS INFORMATION 3V VERSUS 5V PERFORMANCE COMPARISON Table 1. 5V/3V Performance Comparison Table 1 shows the performance comparison between 3V and 5V supplies. The power dissipation drops by a factor of ﬁve when the supply is reduced to 3V. The converter slows down somewhat but still gives excellent performance on a 3V rail. With a 3V supply, the LTC1196 converts in 1.6μs, samples at 450kHz, and provides a 500kHz linearinput bandwidth.
PAGE 24
LTC1196/LTC1198 TYPICAL APPLICATIONS DATA CLK CS B7 B6 B5 B4 B3 B2 B1 B0 70 140 210 280 350 420 490 560 630 700 770 840 910 980 1050 1120 TIME (ns) 1196/98 F14 Figure 14. The Timing Diagram Interfacing the LTC1198 to the TMS320C25 DSP Figure 15 illustrates the interface between the LTC1198 8-bit data acquisition system and the TMS320C25 digital signal processor (DSP).
PAGE 25
LTC1196/LTC1198 TYPICAL APPLICATIONS The timing diagram of Figure 16 was obtained from the circuit of Figure 15. The CLK was 5MHz for the timing diagram and the TMS320C25 clock rate was 40MHz. Figure 17 shows the timing diagram with the LTC1198 running off a 2.7V supply and 5MHz CLK. VERTICAL: 5V/DIV CS CLK DIN DOUT 1196/98 F16 NULL BITS MSB (B7) LSB (B0) HORIZONTAL: 1500ns/DIV Figure 16.
PAGE 26
LTC1196/LTC1198 TYPICAL APPLICATIONS Once RINT is generated the code begins execution at the label RINT. This code stores the DOUT word from the LTC1198 in the ACC and then stores it in location 200 hex. The data appears in location 200 hex right-justiﬁed as shown in Figure 19. The code is set up to continually loop, so at this point the code jumps to label TXRX and repeats from here.
PAGE 27
LTC1196/LTC1198 PACKAGE DESCRIPTION S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 8 .245 MIN 7 6 5 .160 ±.005 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) .030 ±.005 TYP 1 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) 3 4 .053 – .069 (1.346 – 1.752) .004 – .010 (0.101 – 0.254) 0°– 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1.
PAGE 28
LTC1196/LTC1198 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1402 12-Bit, 2.2Msps Serial ADC 5V or ±5V Supply, 4.096V or ±2.5V Span LTC1403/LTC1403A 12-/14-Bit, 2.8Msps Serial ADCs 3V, 15mW, Unipolar Inputs, MSOP Package LTC1403-1/LTC1403A-1 12-/14-Bit, 2.