LTC1096/LTC1096L LTC1098/LTC1098L Micropower Sampling 8-Bit Serial I/O A/D Converters FEATURES DESCRIPTION n 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. n n n n n n n n n 80μA Maximum Supply Current 1nA Typical Supply Current in Shutdown 5V Operation (LTC1096/LTC1098) 3V Operation (LTC1096L/LTC1098L)(2.65V Min) Sample-and-Hold 16μs Conversion Time 33kHz Sample Rate ±0.5LSB Total Unadjusted Error Over Temp Direct 3-Wire Interface to Most MPU Serial Ports and All MPU Parallel I/O Ports 8-Pin SO Plastic Package APPLICATIONS n n n n n n Battery-Operated Systems Remote Data Acquisition Battery Monitoring Battery Gas Gauges Temperature Measurement Isolated Data Acquisition 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. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION 10μW, S8 Package, 8-Bit A/D Samples at 200Hz and Runs Off a 5V Battery 1000 TA = 25°C VCC = VREF = 5V 5V MPU (e.g., 8051) ANALOG INPUT 0V TO 5V RANGE CS/ VCC SHUTDOWN CLK +IN LTC1096 –IN DOUT GND P1.4 P1.3 P1.2 VREF SUPPLY CURRENT, ICC (μA) 1μF Supply Current vs Sample Rate 100 10 10968 TA01 1 0.1 1 10 SAMPLE FREQUENCY, fSMPL (kHz) 100 10968 TA02 10968fc 1 LTC1096/LTC1096L LTC1098/LTC1098L ABSOLUTE MAXIMUM RATINGS (Notes 1 and 2) Supply Voltage (VCC) to GND ...................................12V Voltage Analog and Reference ................ –0.3V to VCC + 0.3V Digital Inputs ........................................ –0.3V to 12V Digital Outputs ........................... –0.3V to VCC + 0.3V Power Dissipation ...............................................500mW Storage Temperature Range................... –65°C to 150°C PIN CONFIGURATION 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 (Note 3) LTC1096 LTC1098 TOP VIEW CS/ 1 SHUTDOWN +IN 2 TOP VIEW 8 VCC 7 CLK –IN 3 6 DOUT GND 4 5 VREF CS/ 1 SHUTDOWN CH0 2 N8 PACKAGE S8 PACKAGE 8-LEAD PLASTIC DIP 8-LEAD PLASTIC SOIC TJMAX = 150°C, θJA = 130°C/W (N8) TJMAX = 150°C, θJA = 175°C/W (S8) 8 VCC(VREF) 7 CLK CH1 3 6 DOUT GND 4 5 DIN N8 PACKAGE S8 PACKAGE 8-LEAD PLASTIC DIP 8-LEAD PLASTIC SOIC TJMAX = 150°C, θJA = 130°C/W (N8) TJMAX = 150°C, θJA = 175°C/W (S8) ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC1096ACN8#PBF LTC1096ACN8#TRPBF LTC1096ACN8 8-Lead Plastic DIP 0°C to 70°C LTC1096ACS8#PBF LTC1096ACS8#TRPBF 1096A 8-Lead Plastic SOIC 0°C to 70°C LTC1096AIN8#PBF LTC1096AIN8#TRPBF LTC1096AIN8 8-Lead Plastic DIP –40°C to 85°C LTC1096AIS8#PBF LTC1096AIS8#TRPBF 1096AI 8-Lead Plastic SOIC –40°C to 85°C LTC1096CN8#PBF LTC1096CN8#TRPBF LTC1096CN8 8-Lead Plastic DIP 0°C to 70°C LTC1096CS8#PBF LTC1096CS8#TRPBF 1096 8-Lead Plastic SOIC 0°C to 70°C LTC1096IN8#PBF LTC1096IN8#TRPBF LTC1096IN8 8-Lead Plastic DIP –40°C to 85°C LTC1096IS8#PBF LTC1096IS8#TRPBF 1096I 8-Lead Plastic SOIC –40°C to 85°C LTC1096LCS8#PBF LTC1096LCS8#TRPBF 1096L 8-Lead Plastic SOIC 0°C to 70°C LTC1096LIS8#PBF LTC1096LIS8#TRPBF 1096LI 8-Lead Plastic SOIC –40°C to 85°C LTC1098ACN8#PBF LTC1098ACN8#TRPBF LTC1098ACN8 8-Lead Plastic DIP 0°C to 70°C LTC1098ACS8#PBF LTC1098ACS8#TRPBF 1098A 8-Lead Plastic SOIC 0°C to 70°C LTC1098CN8#PBF LTC1098CN8#TRPBF LTC1098CN8 8-Lead Plastic DIP 0°C to 70°C LTC1098CS8#PBF LTC1098CS8#TRPBF 1098 8-Lead Plastic SOIC 0°C to 70°C LTC1098IN8#PBF LTC1098IN8#TRPBF LTC1098IN8 8-Lead Plastic DIP –40°C to 85°C LTC1098IS8#PBF LTC1098IS8#TRPBF 1098I 8-Lead Plastic SOIC –40°C to 85°C LTC1098LCS8#PBF LTC1098LCS8#TRPBF 1098L 8-Lead Plastic SOIC 0°C to 70°C LTC1098LIS8#PBF LTC1098LIS8#TRPBF 1098LI 8-Lead Plastic SOIC –40°C to 85°C 10968fc 2 LTC1096/LTC1096L LTC1098/LTC1098L ORDER INFORMATION LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC1096ACN8 LTC1096ACN8#TR LTC1096ACN8 8-Lead Plastic DIP 0°C to 70°C LTC1096ACS8 LTC1096ACS8#TR 1096A 8-Lead Plastic SOIC 0°C to 70°C LTC1096AIN8 LTC1096AIN8#TR LTC1096AIN8 8-Lead Plastic DIP –40°C to 85°C LTC1096AIS8 LTC1096AIS8#TR 1096AI 8-Lead Plastic SOIC –40°C to 85°C LTC1096CN8 LTC1096CN8#TR LTC1096CN8 8-Lead Plastic DIP 0°C to 70°C LTC1096CS8 LTC1096CS8#TR 1096 8-Lead Plastic SOIC 0°C to 70°C LTC1096IN8 LTC1096IN8#TR LTC1096IN8 8-Lead Plastic DIP –40°C to 85°C LTC1096IS8 LTC1096IS8#TR 1096I 8-Lead Plastic SOIC –40°C to 85°C LTC1096LCS8 LTC1096LCS8#TR 1096L 8-Lead Plastic SOIC 0°C to 70°C LTC1096LIS8 LTC1096LIS8#TR 1096LI 8-Lead Plastic SOIC –40°C to 85°C LTC1098ACN8 LTC1098ACN8#TR LTC1098ACN8 8-Lead Plastic DIP 0°C to 70°C LTC1098ACS8 LTC1098ACS8#TR 1098A 8-Lead Plastic SOIC 0°C to 70°C LTC1098CN8 LTC1098CN8#TR LTC1098CN8 8-Lead Plastic DIP 0°C to 70°C LTC1098CS8 LTC1098CS8#TR 1098 8-Lead Plastic SOIC 0°C to 70°C LTC1098IN8 LTC1098IN8#TR LTC1098IN8 8-Lead Plastic DIP –40°C to 85°C LTC1098IS8 LTC1098IS8#TR 1098I 8-Lead Plastic SOIC –40°C to 85°C LTC1098LCS8 LTC1098LCS8#TR 1098L 8-Lead Plastic SOIC 0°C to 70°C LTC1098LIS8 LTC1098LIS8#TR 1098LI 8-Lead Plastic SOIC –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ This product is only offered in trays. For more information go to: http://www.linear.com/packaging/ RECOMMENDED OPERATING CONDITIONS LTC1096/LTC1098 SYMBOL PARAMETER CONDITIONS MIN TYP MAX VCC Supply Voltage LTC1096 LTC1098 3.0 3.0 9 6 500 UNITS V V VCC = 5V Operation fCLK Clock Frequency VCC = 5V 25 tCYC Total Cycle Time LTC1096, fCLK = 500kHz LTC1098, fCLK = 500kHz 29 29 kHz μs μs thDI Hold Time, DIN After CLK↑ VCC = 5V 150 ns tsuCS Setup Time CS↓ Before First CLK↑ (See Operating Sequence) VCC = 5V, LTC1096 VCC = 5V, LTC1098 500 500 ns ns tWAKEUP Wake-Up Time CS↓ Before First CLK↓ After First CLK↑ (See Figure 1 LTC1096 Operating Sequence) VCC = 5V, LTC1096 10 μs Wake-Up Time CS↓ Before MSBF Bit CLK↓ (See Figure 2 LTC1098 Operating Sequence) VCC = 5V, LTC1098 10 μs tsuDI Setup Time, DIN Stable Before CLK↑ VCC = 5V 400 ns tWHCLK CLK High Time VCC = 5V 0.8 μs tWLCLK CLK Low Time VCC = 5V 0.8 μs 10968fc 3 LTC1096/LTC1096L LTC1098/LTC1098L RECOMMENDED OPERATING CONDITIONS LTC1096/LTC1098 SYMBOL PARAMETER CONDITIONS tWHCS CS High Time Between Data Transfer Cycles VCC = 5V MIN 1 TYP MAX UNITS μs tWLCS CS Low Time During Data Transfer LTC1096, fCLK = 500kHz LTC1098, fCLK = 500kHz 28 28 μs μs VCC = 3V Operation fCLK Clock Frequency VCC = 3V 25 tCYC Total Cycle Time LTC1096, fCLK = 250kHz LTC1098, fCLK = 250kHz 58 58 250 kHz μs μs thDI Hold Time, DIN After CLK↑ VCC = 3V 450 ns tsuCS Setup Time CS↓ Before First CLK↑ (See Operating Sequence) VCC = 3V, LTC1096 VCC = 3V, LTC1098 1 1 μs μs tWAKEUP Wake-Up Time CS↓ Before First CLK↓ After First CLK↑ (See Figure 1 LTC1096 Operating Sequence) VCC = 3V, LTC1096 10 μs Wake-Up Time CS↓ Before MSBF Bit CLK↓ (See Figure 2 LTC1098 Operating Sequence) VCC = 3V, LTC1098 10 μs tsuDI Setup Time, DIN Stable Before CLK↑ VCC = 3V 1 μs tWHCLK CLK High Time VCC = 3V 1.6 μs tWLCLK CLK Low Time VCC = 3V 1.6 μs tWHCS CS High Time Between Data Transfer Cycles VCC = 3V 2 μs tWLCS CS Low Time During Data Transfer LTC1096, fCLK = 250kHz LTC1098, fCLK = 250kHz 56 56 μs μs LTC1096L/LTC1098L SYMBOL PARAMETER VCC Supply Voltage fCLK Clock Frequency tCYC CONDITIONS MIN TYP MAX UNITS 2.65 4.0 V VCC = 2.65V 25 250 kHz Total Cycle Time LTC1096L, fCLK = 250kHz LTC1098L, fCLK = 250kHz 58 58 μs μs thDI Hold Time, DIN After CLK↑ VCC = 2.65V 450 ns tsuCS Setup Time CS↓ Before First CLK↑ (See Operating Sequence) VCC = 2.65V, LTC1096L VCC = 2.65V, LTC1098L 1 1 μs μs tWAKEUP Wake-Up Time CS↓ Before First CLK↓ After First CLK↑ (See Figure 1 LTC1096L Operating Sequence) VCC = 2.65V, LTC1096L 10 μs Wake-Up Time CS↓ Before MSBF Bit CLK↓ (See Figure 2 LTC1098L Operating Sequence) VCC = 2.65V, LTC1098L 10 μs tsuDI Setup Time, DIN Stable Before CLK↑ VCC = 2.65V 1 μs tWHCLK CLK High Time VCC = 2.65V 1.6 μs tWLCLK CLK Low Time VCC = 2.65V 1.6 μs tWHCS CS High Time Between Data Transfer Cycles VCC = 2.65V 2 μs tWLCS CS Low Time During Data Transfer LTC1096L, fCLK = 250kHz LTC1098L, fCLK = 250kHz 56 56 μs μs 10968fc 4 LTC1096/LTC1096L LTC1098/LTC1098L CONVERTER AND MULTIPLEXER CHARACTERISTICS LTC1096/LTC1098 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, VREF = 5V, fCLK = 500kHz, unless otherwise noted. LTC1096A/LTC1098A PARAMETER CONDITIONS MIN TYP LTC1096/LTC1098 MAX MIN TYP MAX UNITS Resolution (No Missing Code) l Offset Error l ±0.5 ±0.5 LSB l ±0.5 ±0.5 LSB l ±0.5 ±1.0 LSB l ±0.5 ±1.0 LSB Linearity Error (Note 4) Full Scale Error 8 8 Bits Total Unadjusted Error (Note 5) VREF = 5.000V Analog Input Range (Notes 6, 7) –0.05V to VCC + 0.05V V REF Input Range (Notes 6, 7) 4.5 ≤ VCC ≤ 6V 6V < VCC ≤ 9V, LTC1096 –0.05V to VCC + 0.05V –0.05V to 6V V V Analog Input Leakage Current (Note 8) l ±1.0 ±1.0 μA LTC1096/LTC1098 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted. LTC1096A/LTC1098A PARAMETER CONDITIONS l Resolution (No Missing Code) Offset Error Linearity Error MIN (Notes 4, 9) Full-Scale Error Total Unadjusted Error (Notes 5, 9) VREF = 2.500V Analog Input Range (Notes 6, 7) REF Input Range (Notes 6, 7, 9) 3V ≤ VCC ≤ 6V Analog Input Leakage Current (Notes 8, 9) TYP LTC1096/LTC1098 MAX MIN 8 TYP MAX UNITS 8 Bits l ±0.75 ±1.0 LSB l ±0.5 ±1.0 LSB l ±1.0 ±1.0 LSB l ±1.0 ±1.5 LSB –0.05V to VCC + 0.05V V –0.05V to VCC + 0.05V l V ±1.0 ±1.0 μA LTC1096L/LTC1098L The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 2.65V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted. LTC1096A/LTC1098A PARAMETER CONDITIONS MIN TYP MAX UNITS Resolution (No Missing Code) l Offset Error l ±1.0 LSB l ±1.0 LSB l ±1.0 LSB l ±1.5 LSB Linearity Error (Note 4) Full-Scale Error 8 Bits Total Unadjusted Error (Note 5) VREF = 2.5V Analog Input Range (Notes 6, 7) –0.05V to VCC + 0.05V V REF Input Range (Note 6) 2.65V ≤ VCC ≤ 4.0V –0.05V to VCC + 0.05V V Analog Input Leakage Current (Note 8) l ±1.0 μA 10968fc 5 LTC1096/LTC1096L LTC1098/LTC1098L DIGITAL AND DC ELECTRICAL CHARACTERISTICS LTC1096/LTC1098 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 MIN VIH High Level Input Voltage VCC = 5.25V l VIL Low Level Input Voltage VCC = 4.75V l 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 l l VOL Low Level Output Voltage VCC = 4.75V, IO = 1.6mA l l IOZ Hi-Z Output Leakage CS ≥ VIH ISOURCE Output Source Current VOUT = 0V ISINK Output Sink Current VOUT = VCC IREF Reference Current ICC Supply Current TYP MAX UNITS 2.0 V 0.8 V l 2.5 μA l –2.5 μA 4.5 2.4 4.74 4.72 V V 0.4 V ±3.0 μA –25 mA 45 mA CS = VCC tCYC ≥ 200μs, fCLK ≤ 50kHz tCYC = 29μs, fCLK = 500kHz l l l 0.001 3.500 35.000 2.5 7.5 50.0 μA μA μA CS = VCC l 0.001 3.0 μA LTC1096, tCYC ≥ 200μs, fCLK ≤ 50kHz LTC1096, tCYC = 29μs, fCLK = 500kHz l l 40 120 80 180 μA μA LTC1098, tCYC ≥ 200μs, fCLK ≤ 50kHz LTC1098, tCYC = 29μs, fCLK = 500kHz l l 44 155 88 230 μA μA LTC1096/LTC1098 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3V, VREF = 2.5V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS VIH High Level Input Voltage VCC = 3.6V l MIN VIL Low Level Input Voltage VCC = 3V l TYP MAX 1.9 UNITS V 0.45 V IIH High Level Input Current (Note 9) VIN = VCC l 2.5 μA IIL Low Level Input Current (Note 9) VIN = 0V l –2.5 μA VOH High Level Output Voltage VCC = 3V, IO = 10μA VCC = 3V, IO = 360μA l l VOL Low Level Output Voltage VCC = 3V, IO = 400μA l l 2.3 2.1 2.69 2.64 V V 0.3 V IOZ Hi-Z Output Leakage (Note 9) CS ≥ VIH ISOURCE Output Source Current (Note 9) VOUT = 0V ISINK Output Sink Current (Note 9) VOUT = VCC IREF Reference Current (Note 9) CS = VCC tCYC ≥ 200μs, fCLK ≤ 50kHz tCYC = 58μs, fCLK = 250kHz l l l 0.001 3.500 35.000 2.5 7.5 50.0 μA μA μA ICC Supply Current (Note 9) CS = VCC l 0.001 3.0 μA LTC1096, tCYC ≥ 200μs, fCLK ≤ 50kHz LTC1096, tCYC = 58μs, fCLK = 250kHz l l 40 120 80 180 μA μA LTC1098, tCYC ≥ 200μs, fCLK ≤ 50kHz LTC1098, tCYC = 58μs, fCLK = 250kHz l l 44 155 88 230 μA μA ±3.0 –10 μA mA 15 mA 10968fc 6 LTC1096/LTC1096L LTC1098/LTC1098L DIGITAL AND DC ELECTRICAL CHARACTERISTICS LTC1096L/LTC1098L The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 2.65V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN VIH High Level Input Voltage VCC = 3.6V l VIL Low Level Input Voltage VCC = 2.65V l TYP MAX UNITS 0.45 V 1.9 V IIH High Level Input Current VIN = VCC l 2.5 μA IIL Low Level Input Current VIN = 0V l –2.5 μA VOH High Level Output Voltage VCC = 2.65V, IO = 10μA VCC = 2.65V, IO = 360μA l l VOL Low Level Output Voltage VCC = 2.65V, IO = 400μA l l IOZ Hi-Z Output Leakage CS ≥ High ISOURCE Output Source Current VOUT = 0V ISINK Output Sink Current VOUT = VCC IREF Reference Current ICC Supply Current 2.3 2.1 2.64 2.50 V V 0.3 V ±3.0 μA –10 mA 15 mA CS = VCC tCYC ≥ 200μs, fCLK ≤ 50kHz tCYC = 58μs, fCLK = 250kHz l l l 0.001 3.500 35.000 2.5 7.5 50.0 μA μA μA CS = VCC l 0.001 3.0 μA LTC1096L, tCYC ≥ 200μs, fCLK ≤ 50kHz LTC1096L, tCYC = 58μs, fCLK = 250kHz l l 40 120 80 180 μA μA LTC1098L, tCYC ≥ 200μs, fCLK ≤ 50kHz LTC1098L, tCYC = 58μs, fCLK = 250kHz l l 44 155 88 230 μA μA AC CHARACTERISTICS LTC1096/LTC1098 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, VREF = 5V, fCLK = 500kHz, unless otherwise noted. SYMBOL PARAMETER CONDITIONS tSMPL Analog Input Sample Time See Operating Sequence MIN MAX 1.5 l fSMPL(MAX) Maximum Sampling Frequency TYP UNITS CLK Cycles 33 kHz tCONV Conversion Time See Operating Sequence tdDO Delay Time, CLK↓ to DOUT Data Valid See Test Circuits l 200 8 450 CLK Cycles ns tdis Delay Time, CS↑ to DOUT Hi-Z See Test Circuits l 170 450 ns ten Delay Time, CLK↓ to DOUT Enable See Test Circuits l 60 250 ns thDO Time Output Data Remains Valid After CLK↓ CLOAD = 100pF tf DOUT Fall Time See Test Circuits l 180 70 250 ns ns tr DOUT Rise Time See Test Circuits l 25 100 ns CIN Input Capacitance Analog Inputs On Channel Analog Inputs Off Channel 25 5 pF pF Digital Input 5 pF 10968fc 7 LTC1096/LTC1096L LTC1098/LTC1098L AC CHARACTERISTICS LTC1096/LTC1098 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN tSMPL Analog Input Sample Time See Operating Sequence MAX 1.5 l fSMPL(MAX) Maximum Sampling Frequency TYP UNITS CLK Cycles 16.5 kHz Conversion Time See Operating Sequence tdDO Delay Time, CLK↓ to DOUT Data Valid See Test Circuits (Note 9) l 500 1000 ns tdis Delay Time, CS↑ to DOUT Hi-Z See Test Circuits (Note 9) l 220 800 ns ten Delay Time, CLK↓ to DOUT Enable See Test Circuits (Note 9) l 160 480 ns thDO Time Output Data Remains Valid After CLK↓ CLOAD = 100pF tf DOUT Fall Time See Test Circuits (Note 9) l 70 250 ns tr DOUT Rise Time See Test Circuits (Note 9) l 50 150 ns CIN Input Capacitance Analog Inputs On Channel Analog Inputs Off Channel 25 5 pF pF Digital Input 5 pF tCONV 8 CLK Cycles 400 ns LTC1096L/LTC1098L The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 2.65V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN tSMPL Analog Input Sample Time See Operating Sequence tCONV Conversion Time MAX 1.5 l fSMPL(MAX) Maximum Sampling Frequency TYP See Operating Sequence UNITS CLK Cycles 16.5 kHz 8 CLK Cycles tdDO Delay Time, CLK↓ to DOUT Data Valid See Test Circuits l 500 1000 ns tdis Delay Time, CS↑ to DOUT Hi-Z See Test Circuits l 220 800 ns ten Delay Time, CLK↓ to DOUT Enable See Test Circuits l 160 480 ns thDO Time Output Data Remains Valid After CLK↓ CLOAD = 100pF 400 ns tf DOUT Fall Time See Test Circuits l tr DOUT Rise Time See Test Circuits l CIN Input Capacitance Analog Inputs On Channel Analog Inputs Off Channel 25 5 pF pF Digital Input 5 pF Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: All voltage values are with respect to GND. Note 3: For the 8-lead PDIP, consult the factory. Note 4: Linearity error is specified between the actual and points of the A/D transfer curve. Note 5: Total unadjusted error includes offset, full scale, linearity, multiplexer and hold step errors. Note 6: 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. This means that as long as the reference or 70 250 ns 50 200 ns 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 7: The supply voltage range for the LTC1096L/LTC1098L is from 2.65V to 4V. The supply voltage range for the LTC1096 is from 3V to 9V, but the supply voltage range for the LTC1098 is only from 3V to 6V. Note 8: Channel leakage current is measured after the channel selection. Note 9: These specifications are either correlated from 5V specifications or guaranteed by design. 10968fc 8 LTC1096/LTC1096L LTC1098/LTC1098L TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs Clock Rate for Active and Shutdown Modes VCC = 9V SUPPLY CURRENT, ICC (μA) 150 VCC = 5V 100 50 10 0.002 0 CS = VCC 80 60 “ACTIVE” MODE CS = 0 40 20 0 1 7 3 2 5 6 4 SUPPLY VOLTAGE,VCC (V) Change in Offset vs Reference Voltage LTC1096 0.25 0 1 0 0.50 0.3 0.2 0.1 0 –0.1 –0.2 –0.3 0 1 2 3 4 5 6 7 8 SUPPLY VOLTAGE, VCC (V) 10968 G04 Change in Linearity vs Supply Voltage 0.25 0 –0.25 9 10 –O.50 0 –0.1 –0.2 0.2 0.1 0 –0.1 –0.2 –0.3 –0.3 –0.4 –0.4 0 1 2 3 4 5 6 7 8 SUPPLY VOLTAGE, VCC (V) 9 10 10968 G07 CHANGE IN GAIN (LSB) 0.1 –0.5 5 0.50 0.3 CHANGE IN GAIN (LSB) 0.3 3 4 2 REFERENCE VOLTAGE (V) Change in Gain vs Reference Voltage LTC1096 TA = 25°C VREF = 2.5V FCLK = 100kHz 0.4 0.2 1 10968 G06 0.5 0.4 0 10968 G05 Change in Gain vs Supply Voltage TA = 25°C VREF = 2.5V FCLK = 100kHz TA = 25°C VCC = 5V FCLK = 500kHz –0.4 5 0.5 100 Change in Linearity vs Reference Voltage LTC1096 TA = 25°C VREF = 2.5V FCLK = 100kHz 0.4 –0.5 3 4 2 REFERENCE VOLTAGE (V) 1 10 SAMPLE FREQUENCY, fSMPL (kHz) 10968 G03 0.5 TA = 25°C VCC = 5V FCLK = 500kHz –0.25 CHANGE IN LINEARTY (LSB) 0.1 9 Change in Offset vs Supply Voltage 0.50 –0.5 8 10968 G02 MAGNITUDE OF OFFSET CHANGE (LSB) MAGNITUDE OF OFFSET CHANGE (LSB = 1/256 s VREF) 10968 G01 –0.50 10 1 0 1000 100 “SHUTDOWN” MODE CS = VCC 0.001 10 100 FREQUENCY (kHz) 1 TA = 25°C VCC = VREF = 5V TA = 25°C VREF = 2.5V CHANGE IN LINEARITY (LSB) SUPPLY CURRENT, ICC (μA) 200 1000 100 TA = 25°C CS = 0V Supply Current vs Sample Frequency LTC1096 SUPPLY CURRENT, ICC (μA) 250 Supply Current vs Supply Voltage Active and Shutdown Modes TA = 25°C VCC = 5V FCLK = 500kHz 0.25 0 –0.25 0 1 2 3 4 5 6 7 8 SUPPLY VOLTAGE, VCC (V) 9 10 10968 G08 –O.50 0 1 3 4 2 VOLTAGE REFERENCE (V) 5 10968 G09 10968fc 9 LTC1096/LTC1096L LTC1098/LTC1098L TYPICAL PERFORMANCE CHARACTERISTICS Maximum Clock Frequency vs Source Resistance Maximum Clock Frequency vs Supply Voltage 1.5 VIN + INPUT – INPUT 0.75 RSOURCE– 0.50 0.25 0 1.25 10 RSOURCE– (kΩ) 0.75 0.5 0 2 Minimum Wake-Up Time vs Source Resistance 1 7.5 5.0 RSOURCE+ VIN 2.5 100 + 10 ON CHANNEL 1 10 1 0.01 –60 –40 –20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) 100 RSOURCE (kΩ) 10968 G14 10968 G13 Minimum Clock Frequency for 0.1LSB Error† vs Temperature 10968 G15 ENOBs vs Frequency FFT Plot 0 9 –10 160 8 –20 140 7 120 6 ENOBs VREF = 5V VCC = 5V 100 80 AMPLITUDE (dB) 10 200 180 5 4 60 3 40 2 20 TA = 25°C VCC = VREF = 5V fSMPL = 31.25kHz 1 0 –60 –40 –20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) OFF CHANNEL 0.1 – 10 10968 G12 VREF = 5V VCC = 5V 0 6 8 4 SUPPLY VOLTAGE, VCC (V) 10 1000 LEAKAGE CURRENT (nA) MINIMUM WAKE-UP TIME (μs) 2 6 8 4 SUPPLY VOLTAGE, VCC (V) Input Channel Leakage Current vs Temperature TA = 25°C VREF = 5V 3 2 0 10968 G11 10 2 2 0 10 4 6 8 SUPPLY VOLTAGE (V) 10968 G10 TA = 25°C VREF = 2.5V 0 3 1 0.25 100 4 WAKE-UP TIME (μs) 4 1.0 Wake-Up Time vs Supply Voltage MINIMUM CLOCK FREQUENCY (kHz) TA = 25°C 0 1 0 5 TA = 25°C VREF = 2.5V LOGIC THRESH0LD (V) TA = 25°C VCC = VREF = 5V MAXIMUM CLOCK FREQUENCY (MHz) MAXIMUM CLOCK FREQUENCY* (MHz) 1 Digital Input Logic Threshold vs Supply Voltage 10 FREQUENCY (kHz) 10968 G16 * Maximum CLK frequency represents the clock frequency at which a 0.1LSB shift in the error at any code transition from its 0.75MHz value is first detected. † As the CLK frequency is decreased from 500kHz, minimum CLK frequency (Δerror ≤ 0.1LSB) represents the frequency at which a 0.1LSB shift in any code transition from its 500kHz value is first detected. –30 –40 –50 –60 –70 –80 –90 0 1 TA = 25°C VCC = VREF = 5V fSMPL = 31.25kHz fIN = 5.8kHz 100 10968 G17 –100 0 2 4 10 12 6 8 FREQUENCY (kHz) 14 16 10968 G18 10968fc 10 LTC1096/LTC1096L LTC1098/LTC1098L PIN FUNCTIONS 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. IN+ (Pin 2): Analog Input. This input must be free of noise with respect to GND. CH0 (Pin 2): Analog Input. This input must be free of noise with respect to GND. IN– (Pin 3): Analog Input. This input must be free of noise with respect to GND. CH1 (Pin 3): Analog Input. This input must be free of noise with respect to GND. GND (Pin 4): Analog Ground. GND should be tied directly to an analog ground plane. GND (Pin 4): Analog Ground. GND should be tied directly to an analog ground plane. VREF (Pin 5): Reference Input. The reference input defines the span of the A/D converter and must be kept free of noise with respect to GND. DIN (Pin 5): Digital Data Input. The multiplexer address is shifted into this pin. DOUT (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. VCC (Pin 8): Power Supply Voltage. This pin provides power to the A/D converter. It must be free of noise and ripple by bypassing directly to the analog ground plane. DOUT (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. VCC (VREF)(Pin 8): Power Supply Voltage. This pin provides power and defines the span of the A/D converter. It must be free of noise and ripple by bypassing directly to the analog ground plane. 10968fc 11 LTC1096/LTC1096L LTC1098/LTC1098L BLOCK DIAGRAM LTC1096/LTC1096L CS (DIN) CLK VCC (VCC/VREF) BIAS AND SHUTDOWN CIRCUIT IN+ (CH0) CSAMPLE IN– (CH1) SERIAL PORT DOUT – SAR + MICROPOWER COMPARATOR CAPACITIVE DAC 10968 BD GND VREF PIN NAMES IN PARENTHESES REFER TO THE LTC1098/LTC1098L TEST CIRCUITS On and Off Channel Leakage Current Load Circuit for tdDO, tr and tf 5V ION 1.4V A ON CHANNEL IOFF 3kΩ A DOUT • • • • POLARITY OFF CHANNEL TEST POINT 100pF 10968 TC02 10968 TC01 10968fc 12 LTC1096/LTC1096L LTC1098/LTC1098L TEST CIRCUITS Voltage Waveforms for DOUT Delay Time, tdDO CLK Voltage Waveforms for DOUT Rise and Fall Times, tr, tf VIL VOH DOUT tdDO VOL VOH DOUT tr VOL tf 10968 TC04 10968 TC03 Load Circuit for tdis and ten Voltage Waveforms for tdis CS 2.0V TEST POINT 3k 5V tdis WAVEFORM 2, ten DOUT 100pF tdis WAVEFORM 1 10968 TC05 DOUT WAVEFORM 1 (SEE NOTE 1) 90% tdis 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. 10968 TC06 10968fc 13 LTC1096/LTC1096L LTC1098/LTC1098L TEST CIRCUITS Voltage Waveforms for ten LTC1096/LTC1096L CS tWAKEUP 1 CLK B7 DOUT VOL ten 10968 TC07 LTC1098/LTC1098L CS START DIN CLK 1 2 3 4 5 B7 DOUT VOL ten 10968 TC08 10968fc 14 LTC1096/LTC1096L LTC1098/LTC1098L APPLICATIONS INFORMATION 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. Supply current drops linearly as the sample rate is reduced (see Supply Current vs Sample Rate on the first page of this data sheet). The ADCs automatically power down when not performing conversion, drawing only leakage current. They are packaged in 8-pin SO packages. The LTC1096L/LTC1098L operate on a single supply ranging from 2.65V to 4V. The LTC1096 operates on a single supply ranging from 3V to 9V while the LTC1098 operates from 3V to 6V supplies. The LTC1096/LTC1096L/LTC1098/LTC1098L comprise an 8-bit, switched-capacitor ADC, a sample-and-hold and a serial port (see Block Diagram). Although they share the same basic design, the LTC1096(L) and LTC1098(L) differ in some respects. The LTC1096(L) has a differential input and has an external reference input pin. It can measure signals floating on a DC common mode voltage and can operate with reduced spans down to 250mV. Reducing the span allows it to achieve 1mV resolution. The LTC1098(L) has a 2-channel input multiplexer and can convert either channel with respect to ground or the difference between the two. 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). If the LTC1096(L)/LTC1098(L) are running with clock frequency less than or equal to 100kHz, the wake-up time is inherently provided. Example Two cases are shown at right to illustrate the relationship among wake-up time, setup time and CLK frequency for the LT1096(L). In Case 1 the clock frequency is 100kHz. One clock cycle is 10μs which can be the wake-up time, while half of that can be the setup time. In Case 2 the clock frequency is 50kHz, half of the clock cycle plus the setup time (=1μs) can be the wake-up time. If the CLK frequency is higher than 100kHz, Figure 1 shows the relationship between the wake-up time and setup time. tWAKEUP CS tsu CLK DOUT NULL BIT SERIAL INTERFACE The LTC1098(L) communicates with microprocessors and other external circuitry via a synchronous, half duplex, 4-wire serial interface while the LTC1096(L) uses a 3-wire interface (see Operating Sequence in Figures 1 and 2). Power Down and Wake-Up Time 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 B7 Case 1. Timing Diagram CS tWAKEUP tsu CLK 10μs DOUT 10968 AI Ex Case 2. Timing Diagram 10968fc 15 LTC1096/LTC1096L LTC1098/LTC1098L APPLICATIONS INFORMATION tCYC CS POWER DOWN CLK tsuCS tWAKEUP DOUT HI-Z NULL BIT B7 B6 (MSB) B5 B4 B3 B2 Hi-Z B0 B1 tCONV tCYC CS POWER DOWN CLK tsuCS tWAKEUP DOUT Hi-Z NULL BIT B7 (MSB) B6 B5 B4 B3 B2 B0 B1 B1 B2 B3 B4 B5 B6 B7* tCONV Hi-Z 10968 F01 *AFTER COMPLETING THE DATA TRANSFER, IF FURTHER CLOCKS ARE APPLIED WITH CS LOW, THE ADC WILL OUTPUT ZEROS INDEFINITELY. Figure 1. LTC1096(L) Operating Sequence The wake-up time is inherently provided for the LTC1098(L) with setup time = 1μs (see Figure 2). CS DIN 1 DOUT 1 Data Transfer The CLK synchronizes the data transfer with each bit being transmitted on the falling CLK edge and captured on the rising CLK edge in both transmitting and receiving systems. The LTC1098(L) first receives input data and then transmits back the A/D conversion result (half duplex). Because of the half duplex operation, DIN and DOUT may be tied together allowing transmission over just three wires: CS, CLK and DATA (DIN/DOUT). Data transfer is initiated by a falling chip select (CS) signal. After CS falls the LTC1098(L) looks for a start bit. After the start bit is received, the 3-bit input word is shifted into the DIN input which configures the LTC1098(L) and starts the conversion. After one null bit, the result of the conversion DIN 2 DOUT 2 SHIFT MUX ADDRESS IN 1 NULL BIT SHIFT A/D CONVERSION RESULT OUT 10968 AI01 is output on the DOUT line. At the end of the data exchange CS should be brought high. This resets the LTC1098(L) in preparation for the next data exchange. The LTC1096(L) does not require a configuration input word and has no DIN pin. A falling CS initiates data transferas shown in the LTC1096(L) operating sequence. After CS falls, the first CLK pulse enables DOUT. After one null bit, the A/D conversion result is output on the DOUT line. Bringing CS high resets the LTC1096(L) for the next data exchange. 10968fc 16 LTC1096/LTC1096L LTC1098/LTC1098L APPLICATIONS INFORMATION 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 B1 Hi-Z B0* 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 B1 B0 B1 B2 B3 B4 B5 B6 B7* tCONV Hi-Z 10968 F02 *AFTER COMPLETING THE DATA TRANSFER, IF FURTHER CLOCKS ARE APPLIED WITH CS LOW, THE ADC WILL OUTPUT ZEROS INDEFINITELY. Figure 2. LTC1098(L) Operating Sequence Example: Differential Inputs (CH+, CH–) Input Data Word Start Bit 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. The first “logical one” clocked into the DIN input after CS goes low is the start bit. The start bit initiates the data transfer. The LTC1098(L) will ignore all leading zeros which precede this logical one. After the start bit is received, the remaining bits of the input word will be clocked in. Further inputs on the DIN pin are then ignored until the next CS cycle. The LTC1098(L) clocks data into the DIN input on the rising edge of the clock. The input data words are defined as follows: START SGL/ DIFF ODD/ MSBF SIGN MUX MSB-FIRST/ ADDRESS LSB-FIRST 10968 AI02 10968fc 17 LTC1096/LTC1096L LTC1098/LTC1098L APPLICATIONS INFORMATION Multiplexer (MUX) Address Unipolar Transfer Curve The bits of the input word following the START bit assign the MUX configuration for the requested conversion. For a given channel selection, the converter will measure the voltage between the two channels indicated by the “+” and “–” signs in the selected row of the followintg tables. In single-ended mode, all input channels are measured with respect to GND. The LTC1096(L)/LTC1098(L) are permanently configured for unipolar only. The input span and code assignment for this conversion type are shown in the following figures for a 5V reference. 11111111 LTC1098(L) Channel Selection SINGLE-ENDED MUX MODE GND – – • • • 00000001 00000000 VIN VREF MSB-First/LSB-First (MSBF) The output data of the LTC1098(L) is programmed for MSB-first or LSB-first sequence using the MSBF bit. When the MSBF bit is a logical one, data will appear on the DOUT line in MSB-first format. Logical zeros will be filled in indefinitely following the last data bit. When the MSBF bit is a logical zero, LSB-first data will follow the normal MSB-first data on the DOUT line. (see Operating Sequence) VREF–1LSB VREF–2LSB 10968 AI03 1LSB CHANNEL # 1 0 + + – + + – 11111110 0V DIFFERENTIAL MUX MODE MUX ADDRESS SGL/DIFF ODD/SIGN 1 0 1 1 0 0 0 1 Unipolar Transfer Curve 10968 AI04 Unipolar Output Code OUTPUT CODE INPUT VOLTAGE INPUT VOLTAGE (VREF = 5.000V) 11111111 11111110 • • • 00000001 00000000 VREF – 1LSB VREF – 2LSB • • • 1LSB 0V 4.9805V 4.9609V • • • 0.0195V 0V 10968 AI05 Operation with DIN and DOUT Tied Together The LTC1098(L) can be operated with DIN and DOUT tied together. This eliminates one of the lines required to communicate to the microprocessor (MPU). Data is transmitted in both directions on a single wire. The processor pin connected to this data line should be configurable as either an input or an output. The LTC1098(L) will take control of 10968fc 18 LTC1096/LTC1096L LTC1098/LTC1098L APPLICATIONS INFORMATION 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 10968 F03 Figure 3. LTC1098(L) Operation with DIN and DOUT Tied Together In the Typical Applications section, there is an example of interfacing the LTC1098(L) with DIN and DOUT tied together to the Intel 8051 MPU. ACHIEVING MICROPOWER PERFORMANCE With typical operating currents of 40μA and automatic shutdown between conversions, the LTC1096/LTC1098 achieves extremely low power consumption over a wide range of sample rates (see Figure 4). In systems that convert continuously, the LTC1096/LTC1098 will draw its normal operating power continuously. Figure 5 shows that the typical current varies from 40μA at clock rates below 50kHz to 100μA at 500kHz. Several things must be taken into account to achieve such a low power consumption. SUPPLY CURRENT vs CLOCK RATE FOR ACTIVE AND SHUTDOWN MODES 140 120 SUPPLY CURRENT, ICC (μA) the data line and drive it low on the 4th falling CLK edge after the start bit is received (see Figure 3). Therefore the processor port line must be switched to an input before this happens, to avoid a conflict. TA = 25°C VCC = 5V 100 80 60 40 20 0.002 1000 0 100 SUPPLY CURRENT, ICC (μA) TA = 25°C VCC = 5V ACTIVE (CS LOW) SHUTDOWN (CS HIGH) 10k 100k 1k CLOCK FREQUENCY (Hz) 1M 10968 F05 Figure 5. After a Conversion, When the Microprocessor Drives CS High, the ADC Automatically Shuts Down Until the Next Conversion. The Supply Current, Which Is Very Low During cConversions, Drops to Zero in Shutdown 100 10 Shutdown 1 0.1 1 10 Sample Rate, fSAMPLE (kHz) 100 10968 F04 Figure 4. Automatic Power Shutdown Between Conversions Allows Power Consumption to Drop with Sample Rate Figures 1 and 2 show the operating sequence of the LTC1096/LTC1098. The converter draws power when the CS pin is low and powers itself down when that pin is high. If the CS pin is not taken to ground when it is low and not taken to supply voltage when it is high, the input buffers 10968fc 19 LTC1096/LTC1096L LTC1098/LTC1098L APPLICATIONS INFORMATION of 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. The status of the DIN and CLK input have no effect on supply current during this time. There is no need to stop DIN and CLK with CS = high, except the MPU may benefit. Minimize CS Low Time In systems that have significant time between conversions, lowest power drain will occur with the minimum CS low time. Bringing CS low, waiting 10μs for the wake-up time, transferring data as quickly as possible, and then bringing it back high will result in the lowest current drain. This minimizes the amount of time the device draws power. Even though the device draws more power at high clock rates, the net power is less because the device is on for a shorter time. Wake-Up Time A 10μs wake-up time must be provided for the ADCs to convert correctly on a 5V supply. The wake-up time is typically less than 3μs over the supply voltage range (see typical curve of Wake-Up Time vs Supply Voltage). With 10μs wake-up time provided over the supply range, the ADCs will have adequate time to wake up and acquire input signals. Input Logic Levels The input logic levels of CS, CLK and DIN are made to meet TTL on 5V supply. When the supply voltage varies, the input logic levels also change. For the LTC1096/LTC1098 to sample and convert correctly, the digital inputs have to meet logic low and high levels relative to the operating supply voltage (see typical curve of Digital Input Logic Threshold vs Supply Voltage). If achieving micropower consumption is desirable, the digital inputs must go railto-rail between supply voltage and ground (see ACHIEVING MICROPOWER PERFORMANCE section). Clock Frequency DOUT Loading Capacitive loading on the digital output can increase power consumption. A 100pF capacitor on the DOUT pin can more than double the 100μA supply current drain at a 500kHz clock frequency. An extra 100μA or so of current goes into charging and discharging the load capacitor. The same goes for digital lines driven at a high frequency by any logic. The CxVxf currents must be evaluated and the troublesome ones minimized. Lower Supply Voltage For lower supply voltages, LTC offers the LTC1096L/ LTC1098L. These pin compatible devices offer specified performance to 2.65VMIN supply. OPERATING ON OTHER THAN 5V SUPPLIES The LTC1096 operates from 3V to 9V supplies and the LTC1098 operates from 3V to 6V supplies. To operate the LTC1096/LTC1098 on other than 5V supplies, a few things must be kept in mind. The maximum recommended clock frequency is 500kHz for the LTC1096/LTC1098 running off a 5V supply. With the supply voltage changing, the maximum clock frequency for the devices also changes (see the typical curve of Maximum Clock Rate vs Supply Voltage). If the maximum clock frequency is used, care must be taken to ensure that the device converts correctly. Mixed Supplies It is possible to have a microprocessor running off a 5V supply and communicate with the LTC1096/LTC1098 operating on 3V or 9V supplies. The requirement to achieve this is that the outputs of CS, CLK and DIN from the MPU have to be able to trip the equivalent inputs of the ADCs and the output of DOUT from the ADCs must be able to toggle the equivalent input of the MPU (see typical curve of Digital Input Logic Threshold vs Supply Voltage). With the LTC1096 operating on a 9V supply, the output of DOUT may go between 0V and 9V. The 9V output may damage the MPU running off a 5V supply. The way to get around this possibility is to have a resistor divider on DOUT 10968fc 20 LTC1096/LTC1096L LTC1098/LTC1098L APPLICATIONS INFORMATION (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 9V 4.7μF SAMPLE-AND-HOLD MPU (e.g. 8051) DIFFERENTIAL INPUTS COMMON MODE RANGE 0V TO 6V CS VCC +IN CLK –IN DOUT GND VREF 5V P1.4 P1.3 50k P1.2 6V The VCC pin should be bypassed to the ground plane with a 1μF tantalum with leads as short as possible. If power supply is clean, the LTC1096(L)/LTC1098(L) can also operate with smaller 0.1μF surface mount or ceramic bypass capacitors. All analog inputs should be referenced directly to the single point ground. Digital inputs and outputs should be shielded from and/or routed away from the reference and analog circuitry. 50k LTC1096 10968 F06 Figure 6. Interfacing a 9V Powered LTC1096 to a 5V System Both the LTC1096(L) and the LTC1098(L) provide a built-in sample-and-hold (S&H) function to acquire signals. The S&H of the LTC1096(L) acquires input signals from “+” input relative to “–” input during the tWAKEUP time (see Figure 1). However, the S&H of the LTC1098(L) can sample input signals in the single-ended mode or in the differential inputs during the tSMPL time (see Figure 7). Single-Ended Inputs BOARD LAYOUT CONSIDERATIONS Grounding and Bypassing The LTC1096(L)/LTC1098(L) should be used with an analog ground plane and single point grounding techniques. The GND pin should be tied directly to the ground plane. The sample-and-hold of the LTC1098(L) 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 MSBF bit is shifted SAMPLE HOLD "+" INPUT MUST SETTLE DURING THIS TIME CS tSMPL tCONV CLK DIN START SGL/DIFF MSBF DOUT DON'T CARE B7 1ST BIT TEST "–" INPUT MUST SETTLE DURING THIS TIME "+" INPUT "–" INPUT 10968 F07 Figure 7. LTC1098(L) “+” and “–” Input Settling Windows 10968fc 21 LTC1096/LTC1096L LTC1098/LTC1098L APPLICATIONS INFORMATION 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. In this case, the voltage on the selected “+” input is still sampled and held and therefore may be rapidly time varying just as in single-ended mode. However, the voltage on the selected “–” input must remain constant and be free of noise and ripple throughout the conversion time. Otherwise, the differencing operation may not be performed accurately. The conversion time is 8 CLK cycles. Therefore, a change in the “–” input voltage during this interval can cause conversion errors. For a sinusoidal voltage on the “–” input this error would be: VERROR (MAX) = VPEAK • 2 • π • f(“–”) • 8/fCLK Where f(“–”) is the frequency of the “–” input voltage, VPEAK is its peak amplitude and fCLK is the frequency of the CLK. In most cases VERROR will not be significant. For a 60Hz signal on the “–” input to generate a 1/4LSB error (5mV) with the converter running at CLK = 500kHz, its peak value would have to be 750mV. ANALOG INPUTS Because of the capacitive redistribution A/D conversion techniques used, the analog inputs of the LTC1096(L)/ LTC1098(L )have capacitive switching input current spikes. These current spikes settle quickly and do not cause a problem. However, if large source resistances are used or if slow settling op amps drive the inputs, care must be taken to ensure that the transients caused by the current spikes settle completely before the conversion begins. “+” Input Settling The input capacitor of the LTC1096(L) is switched onto “+” input during the wake-up time (see Figure 1) and samples the input signal within that time. However, the input capacitor of the LTC1098(L) is switched onto “+” input during the sample phase (tSMPL, see Figure 7). The sample phase is 1.5 CLK cycles before conversion starts. The voltage on the “+” input must settle completely within t WAKEUP or tSMPL for the LTC1096(L) or the LTC1098(L) respectively. Minimizing RSOURCE+ and C1 will improve the input settling time. If a large “+” input source resistance must be used, the sample time can be increased by using a slower CLK frequency. “–” Input Settling At the end of the tWAKEUP or tSMPL, the input capacitor switches to the “–” input and conversion starts (see Figures 1 and 7). During the conversion the “+” input voltage is effectively “held” by the sample-and-hold and will not affect the conversion result. However, it is critical that the “–” input voltage settles completely during the first CLK cycle of the conversion time and be free of noise. Minimizing RSOURCE– and C2 will improve settling time. If a large “–” input source resistance must be used, the time allowed for settling can be extended by using a slower CLK frequency. Input Op Amps When driving the analog inputs with an op amp it is important that the op amp settle within the allowed time (see Figure 7). Again, the “+” and “–” input sampling times can be extended as described above to accommodate slower op amps. Most op amps, including the LT1006 and LT1413 single supply op amps, can be made to settle well even with the minimum settling windows of 3μs (“+” input) which occur at the maximum clock rate of 500kHz. Source Resistance The analog inputs of the LTC1096/LTC1098 look like a 25pF capacitor (CIN) in series with a 500Ω resistor (RON) as shown in Figure 8. CIN gets switched between the selected “+” and “–” inputs once during each conversion cycle. RSOURCE + “+” INPUT LTC1096 LTC1098 VIN + C1 RSOURCE – “–” INPUT RON = 500Ω CIN = 25pF VIN – C2 10968 F08 Figure 8. Analog Input Equivalent Circuit 10968fc 22 LTC1096/LTC1096L LTC1098/LTC1098L APPLICATIONS INFORMATION 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., 1μF), the capacitive input switching currents are averaged into a net DC current. Therefore, a filter should be chosen with a small resistor and large capacitor to prevent DC drops across the resistor. The magnitude of the DC current is approximately IDC = 25pF(VIN /tCYC) and is roughly proportional to VIN. When running at the minimum cycle time of 29μs, the input current equals 4.3μA at VIN = 5V. In this case, a filter resistor of 390Ω will cause 0.1LSB of fullscale error. If a larger filter resistor must be used, errors can be eliminated by increasing the cycle time. RFILTER IDC “+” VIN CFILTER LTC1098 capacitive current spike will be generated on the reference pin by the ADC. These current spikes settle quickly and do not cause a problem. Using a slower CLK will allow more time for the reference to settle. Even at the maximum CLK rate of 500kHz most references and op amps can be made to settle within the REF+ 5 ROUT VREF LTC1096 EVERY CLK CYCLE RON GND 4 5pF TO 30pF 10968 F10 Figure 10. Reference Input Equivalent Circuit 2μs bit time. Reduced Reference Operation The minimum reference voltage of the LTC1098 is limited to 3V because the VCC supply and reference are internally tied together. However, the LTC1096 can operate with reference voltages below 1V. “–” 10968 F09 Figure 9. RC Input Filtering Input Leakage Current The effective resolution of the LTC1096 can be increased by reducing the input span of the converter. The LTC1096 exhibits good linearity and gain over a wide range of reference voltages (see typical curves of Linearity and Full Scale Error vs Reference Voltage). However, care must be taken when operating at low values of VREF because of the reduced LSB step size and the resulting higher accuracy requirement placed on the converter. The following factors must be considered when operating at low VREF values. Input leakage currents can also create errors if the source resistance gets too large. For instance, the maximum input leakage specification of 1μA (at 125°C) flowing through a source resistance of 3.9k will cause a voltage drop of 3.9mV or 0.2LSB. This error will be much reduced at lower temperatures because leakage drops rapidly (see typical curve of Input Channel Leakage Current vs Temperature). 1. Offset 2. Noise 3. Conversion speed (CLK frequency) REFERENCE INPUTS Offset with Reduced VREF The voltage on the reference input of the LTC1096 defines the voltage span of the A/D converter. The reference input transient capacitive switching currents due to the switched-capacitor conversion technique (see Figure 10). During each bit test of the conversion (every CLK cycle), a The offset of the LTC1096 has a larger effect on the output code when the ADC is operated with reduced reference voltage. The offset (which is typically a fixed voltage) becomes a larger fraction of an LSB as the size of the LSB is reduced. The typical curve of Unadjusted Offset Error vs Reference Voltage shows how offset in LSBs is 10968fc 23 LTC1096/LTC1096L LTC1098/LTC1098L APPLICATIONS INFORMATION Noise with Reduced VREF The total input referred noise of the LTC1096 can be reduced to approximately 1mV peak-to-peak 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. For operation with a 5V reference, the 1mV noise is only 0.05LSB peak-to-peak. In this case, the LTC1096 noise will contribute virtually no uncertainty to the output code. However, for reduced references, the noise may become a significant fraction of an LSB and cause undesirable jitter in the output code. For example, with a 1V reference, this same 1mV noise is 0.25LSB peak-to-peak. This will reduce the range of input voltages over which a stable output code can be achieved by 1LSB. If the reference is further reduced to 200mV, the 1mV noise becomes equal to 1.25LSBs and a stable code may be difficult to achieve. In this case averaging readings may be necessary. This noise data was taken in a very clean setup. Any setupinduced noise (noise or ripple on VCC, VREF or VIN) will add to the internal noise. The lower the reference voltage to be used, the more critical it becomes to have a clean, noise free setup. Conversion Speed with Reduced VREF With reduced reference voltages the LSB step size is reduced and the LTC1096 internal comparator overdrive is reduced. Therefore, it may be necessary to reduce the maximum CLK frequency when low values of VREF are used. Input Divider It is OK to use an input divider on the reference input of the LTC1096 as long as the reference input can be made to settle within the bit time at which the clock is running. When using a larger value resistor divider on the reference input the “–” input should be matched with an equivalent resistance. Bypassing Reference Input with Divider Bypassing the reference input with a divider is also possible. However, care must be taken to make sure that the DC voltage on the reference input will not drop too much below the intended reference voltage. AC PERFORMANCE Two commonly used figures of merit for specifying the dynamic performance of the ADCs in digital signal processing applications are the signal-to-noise ratio (SNR) and the effective number of bits (ENOBs). Signal-to-Noise Ratio The signal-to-noise ratio (SNR) is the ratio between the RMS amplitude of the fundamental input frequency to the RMS amplitude of all other frequency components at the A/D output. This includes distortion as well as noise products and for this reason it is sometimes referred to as signal-to-noise + distortion [S/(N + D)]. The output is band limited to frequencies from DC to one half the sampling frequency. Figure 11 shows spectral content from DC to 15.625kHz which is 1/2 the 31.25kHz sampling rate. 0 –10 fSAMPLE = 31.25kHz fIN = 11.8kHz –20 AMPLITUDE (dB) related to 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. –30 –40 –50 –60 –70 –80 –90 –100 –110 –120 0 2 4 10 12 8 6 FREQUENCY (kHz) 14 16 10968 F11 Figure 11. This Clean FFT of an 11.8kHz Input Shows Remarkable Performance for an ADC That Draws Only 100μA When Sampling at the 31.25kHz Rate 10968fc 24 LTC1096/LTC1096L LTC1098/LTC1098L APPLICATIONS INFORMATION Effective Number of Bits EFFECTIVE NUMBER OF BITS (ENOBs) 8 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. Above 40kHz the ENOBs gradually decline, as shown in Figure 12, due to increasing second harmonic distortion. The noise floor remains approximately 70dB. fSAMPLE = 31.25kHz 7 6 5 4 3 2 1 0 20 0 40 INPUT FREQUENCY (kHz) 10968 F12 Figure 12. Dynamic Accuracy Is Maintained Up to an Input Frequency of 40kHz TYPICAL APPLICATIONS MICROPROCESSOR INTERFACES The LTC1096(L)/LTC1098(L) can interface directly (without external hardware to most popular microprocessor (MPU) synchronous serial formats (see Table 1). If an MPU without a dedicated serial port is used, then three or four of the MPU’s parallel port lines can be programmed to form the serial link to the LTC1096(L)/LTC1098(L). Included here is one serial interface example and one example showing a parallel port programmed to form the serial interface. Motorola SPI (MC68HC05C4,CM68HC11) The MC68HC05C4 has been chosen as an example of an MPU with a dedicated serial port. This MPU transfer data MSB-first and in 8-bit increments. With two 8-bit transfers, the A/D result is read into the MPU. The first 8-bit transfer sends the DIN word to the LTC1098(L) and clocks into the processor. The second 8-bit transfer clocks the A/D conversion result, B7 through B0, into the MPU. ANDing the first MUP received byte with 00Hex clears the first byte. Notice how the position of the start bit in the first MPU transmit word is used to position the A/D result right-justified in two memory locations. Table 1. Microprocessor with Hardware Serial Interfaces Compatible with the LTC1096(L)/LTC1098(L) PART NUMBER TYPE OF INTERFACE Motorola MC6805S2,S3 MC68HC11 MC68HC05 SPI SPI SPI RCA CDP68HC05 SPI Hitachi HD6305 HD63705 HD6301 HD63701 HD6303 HD64180 SCI Synchronous SCI Synchronous SCI Synchronous SCI Synchronous SCI Synchronous CSI/O National Semiconductor COP400 Family COP800 Family NS8050U HPC16000 Family MICROWIRE™ MICROWIRE/PLUS™ MICROWIRE/PLUS MICROWIRE/PLUS Texas Instruments TMS7002 TMS7042 TMS70C02 TMS70C42 TMS32011* TMS32020 Serial Port Serial Port Serial Port Serial Port Serial Port Serial Port * Requires external hardware MICROWIRE and MICROWIRE/PLUS are trademarks of National Semiconductor Corp. 10968fc 25 LTC1096/LTC1096L LTC1098/LTC1098L TYPICAL APPLICATIONS Data Exchange Between LTC1098(L) and MC68HC05C4 START BIT MPU TRANSMIT WORD 0 0 0 BYTE 1 SGL/ ODD/ MSBF X DIFF SIGN 1 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 Hardware and Software Interface to Motorola MC68HC05C4 CS C0 SCK MC68HC05C4 MISO CLK ANALOG INPUTS LTC1098 DIN DOUT MOSI 2ND TRANSFER LABEL MNEMONIC START BCLRn LDA STA TST BPL LDA 10968 TA04 STA AND STA TST BPL DOUT from LTC1098(L) Stored in MC68HC05C4 LOCATION A 0 0 0 0 0 0 0 0 BYTE 1 BSETn LDA LSB LOCATION A + 1 B7 B6 B5 B4 B3 B2 B1 B0 10968 TA05 BYTE 2 STA 10968 TA03 COMMENTS Bit 0 Port C goes low (CS goes low) Load LTC1098(L) DIN word into Acc. Load LTC1098(L) DIN word into SPI from Acc. Transfer begins. Test status of SPIF Loop to previous instruction if not done with transfer Load contents of SPI data register into Acc. (DOUT MSBs) Start next SPI cycle Clear the first DOUT word Store in memory location A (MSBs) Test status of SPIF Loop to previous instruction if not done with transfer Set B0 of Port C (CS goes high) Load contents of SPI data register into Acc. (DOUT LSBs) Store in memory location A + 1 (LSBs) 10968fc 26 LTC1096/LTC1096L LTC1098/LTC1098L TYPICAL APPLICATIONS 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. However, we will demonstrate here an interface with the DIN and DOUT of the LTC1098(L) tied together as described in the SERIAL INTERFACE section. This saves one wire. LOOP 1 LOOP The 8051 first sends the start bit and MUX address to the LTC1098(L) over the data line connected to P1.2. Then P1.2 is reconfigured as an input (by writing to it a one) and the 8051 reads back the 8-bit A/D result over the same data line. ANALOG INPUTS CS LTC1098(L) CLK DOUT DIN P1.4 P1.3 P1.2 MNEMONIC OPERAND COMMENTS MOV SETB CLR MOV RLC CLR MOV SETB DJNZ MOV CLR MOV MOV RLC SETB CLR DJNZ MOV SETB A, #FFH P1.4 P1.4 R4, #04 A P1.3 P1.2, C P1.3 R4, LOOP 1 P1, #04 P1.3 R4, #09 C, P1.2 A P1.3 P1.3 R4, LOOP R2, A P1.4 DIN word for LTC1098(L) Make sure CS is high CS goes low Load counter Rotate DIN bit into Carry CLK goes low Output DIN bit to LTC1098(L) CLK goes high Next bit Bit 2 becomes an input CLK goes low Load counter Read data bit into Carry Rotate data bit into Acc. CLK goes high CLK goes low Next bit Store MSBs in R2 CS goes high DOUT from LTC1098(L) Stored in 8051 RAM 8051 MSB MUX ADDRESS R2 A/D RESULT B7 LSB B6 B5 B4 B3 B2 B1 10968 TA06 B0 10968 TA07 MSBF BIT LATCHED BY LTC1098(L) CS 1 2 START SGL/ DIFF 3 4 CLK DATA (DIN/DOUT) ODD/ SIGN MSBF 8051 P1.2 OUTPUTS DATA TO LTC1098(L) 8051 P1.2 RECONFIGURED AS AN INPUT AFTER THE 4TH RISING CLK AND BEFORE THE 4TH FALLING CLK B7 B6 B5 B4 B3 B2 LTC1098(L) SENDS A/D RESULT BACK TO 8051 P1.2 B1 B0 10968 TA08 LTC1098(L) TAKES CONTROL OF DATA LINE ON 4TH FALLING CLK 10968fc 27 LTC1096/LTC1096L LTC1098/LTC1098L A “Quick Look” Circuit for the LTC1096 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. The output data from the DOUT pin can be viewed on an oscilloscope that is set up to trigger on the falling edge of CS (Figure 14). Note the LSB data is partially clocked out before CS goes high. CS CLK DOUT 10968 F14 4.7μF MSB (B7) NULL BIT 5V VIN CLR VCC RC CLK QA A QB B 74C161 QC C QD D T P LOAD GND VCC CH0 CLK LTC1096 CH1 DOUT GND LSB DATA (B1) VERTICAL: 5V/DIV HORIZONTAL: 10μs/DIV + CS LSB (B0) VREF 5V Figure 14. Scope Trace the LTC1096 “Quick Look” Circuit Showing A/D Output 10101010 (AAHEX) 3V 0.1μF LM134 75k 678Ω VCC CLOCK IN 150kHz MAX TO OSCILLOSCOPE CS +IN 10968 F13 13.5k Figure 13. “Quick Look” Circuit for the LTC1096 Figure 15 shows a temperature measurement system. The LTC1096 is connected directly to the low cost silicon temperature sensor. The voltage applied to the VREF pin adjusts the full scale of the A/D to the output range of the sensor. The zero point of the converter is matched to the zero output voltage of the sensor by the voltage on the LTC1096’s negative input. –IN LTC1096 CLK TO μP 182k VREF LT1004-1.2 0.01μF DOUT GND 0.01μF 63.4k 10968 F15 Figure 15. The LTC1096’s High Impedance Input Connects Directly to This Temperature Sensor, Eliminating Signal Conditioning Circuitry in This 0°C to 70°C Thermometer 10968fc 28 LTC1096/LTC1096L LTC1098/LTC1098L 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. The system consumes only 50μA at a sample rate of 10Hz (1ms on-time and 99ms off-time). This is easily within the current supplied by the charge pump running at 5MHz. If a truly isolated system is required, the system’s low power simplifies generating an isolated supply or powering the system from a battery. FLOATING SYSTEM 1N5817 + 0.001μF 2kV 2N3904 47μF 0.1μF 75k 1N5817 0.022μF VCC 100k CS 5MHz LT1004-2.5 LTC1096 1N5817 300Ω CLK 100k CLK VREF 20k +IN –IN ANALOG INPUT DOUT GND 1k 10k DATA 500k 10968 F16 Figure 16. Power for This Floating A/D System Is Provided by a Simple Capacitor Diode Charge Pump. The Two Optoisolators Draw No Current Between Samples, Turning On Only to Send the Clock and Receive Data 10968fc 29 LTC1096/LTC1096L LTC1098/LTC1098L PACKAGE DESCRIPTION N8 Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .400* (10.160) MAX 8 7 6 5 1 2 3 4 .255 ± .015* (6.477 ± 0.381) .300 – .325 (7.620 – 8.255) .008 – .015 (0.203 – 0.381) ( +.035 .325 –.015 8.255 +0.889 –0.381 ) .045 – .065 (1.143 – 1.651) .130 ± .005 (3.302 ± 0.127) .065 (1.651) TYP .100 (2.54) BSC .120 (3.048) .020 MIN (0.508) MIN .018 ± .003 (0.457 ± 0.076) N8 1002 NOTE: 1. DIMENSIONS ARE INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm) 10968fc 30 LTC1096/LTC1096L LTC1098/LTC1098L 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. DIMENSIONS IN 2 .014 – .019 (0.355 – 0.483) TYP INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) .050 (1.270) BSC SO8 0303 10968fc Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 31 LTC1096/LTC1096L LTC1098/LTC1098L TYPICAL APPLICATION 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. The other half of the LTC1178 is used to provide low battery detection. The circuit’s 70μA supply current is dominated by the op amps and the reference. The circuit can be located near the battery and data transmitted serially to the microprocessor. 0.1μF 0.1μF 3V TO 6V 73.2k 470k 750k L O A D 24.9k 0.02Ω FOR 2A FULL SCALE 0.2Ω FOR 0.2A FULL SCALE + CS 1/2 LT1178 – VCC CLK LTC1096 D OUT GND VREF + – TO μP 20M + LO BATTERY 1/2 LT1178 LT1004-1.2 470k – 10968 F17 Figure 17. This 0A to 2A Battery Current Monitor Draws Only 70μA from a 3V Battery RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1196/LTC1198 8-Pin SO, 1Msps, 8-Bit ADCs Low Power, Small Size, Low Cost LTC1286/LTC1298 8-Pin SO, 5V Micropower, 12-Bit ADCs 1- or 2-Channel, Auto Shutdown LTC1285/LTC1298 8-Pin SO, 3V Micropower, 12-Bit ADCs 1- or 2-Channel, Auto Shutdown LTC1400 5V High Speed,Serial 12-Bit ADC 400ksps, Complete with VREF, CLK, Sample-and-Hold LTC1594/LTC1598 4- and 8-Channel, 5V Micropower, 12-Bit ADCs Low Power, Small Size, Low Cost LTC1594L/LTC1598L 4- and 8-Channel, 3V Micropower, 12-Bit ADCs Low Power, Small Size, Low Cost 10968fc 32 Linear Technology Corporation LT 0708 REV C • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 1994