ICM7722 ICm ic TM IC M ICROSYSTEM S 12-Bit 1.2V Low Power Rail-to-Rail Voltage Output Dual DAC FEATURES OVERVIEW • 12-Bit 1.2v Dual DAC in 8 Lead TSSOP Package • Rail-to-Rail Voltage Output • Ultra-Low Power Consumption • Guaranteed Monotonic • Wide Voltage Output Swing Buffer • Three-wire SPI/QSPI and Micro-wire Interface Compatible • Schmitt-Triggered Inputs for Direct Interfacing to opto-couplers The ICM7722 is a 12-Bit Voltage Output, Ultra Low Power, Dual DAC, with guaranteed monotonic behavior. This DAC is available in 8- Lead TSSOP package. The input interface is an easy to use three-wire SPI, QSPI and Micro-wire compatible interface. The DAC has schmitt-triggered inputs for direct interfacing to opto-couplers easily. BLOCK DIAGRAM REFIN APPLICATION • • • • Battery-Powered Applications Audio Applications Industrial Process Control Digital Gain and Offset Adjustment ICM7722 VOA INPUT REGISTER A DAC REGISTER A DAC A AMPLIFIER VOB INPUT REGISTER B DAC REGISTER B DAC B AMPLIFIER INPUT CONTROL LOGIC, REGISTERS AND LATCHES CS Rev A0.1 SDI ICmic reserves the right to change specifications without prior notice SCK 1 ICM7722 PACKAGE 08 Lead TSSOP SCK 1 8 VOA SDI 2 7 VDD CS 3 6 REFIN GND 4 5 VOB TOP VIEW PIN DESCRIPTION (8 Lead TSSOP) Pin Name I/O Description 1 2 SCK SDI I I Serial Clock Input (CMOS) Serial Data Input (CMOS) 3 CS I Active Low Chip Select (CMOS) 4 GND I Ground 5 VOB O DAC B Output Voltage 6 REFIN I Reference Voltage Input 7 VDD I Supply voltage 8 VOA O DAC A Output Voltage ABSOLUTE MAXIMUM RATINGS Symbol Parameter VDD Supply Voltage IIN Input Current VIN Digital Input Voltage (SCK, SDI, CS ) Value Unit 0.9 to 1.32 V +/- 25.0 mA -0.3 to 1.32 V VIN_REF Reference Input Voltage -0.3 to 1.32 V TSTG Storage Temperature -65 to +150 oC TSOL Soldering Temperature 300 oC Stress greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability. Rev A0.1 ICmic reserves the right to change specifications without prior notice 2 ICM7722 ORDERING INFORMATION Part Operating Temperature Range Package -40 oC to 85 oC 08-Lead TSSOP ICM7722 DC ELECTRICAL CHARACTERISTICS (Specification: VDD=1.2V, VREFIN=1.15v, Temp=25°C, unless otherwise specified) Symbol Parameter Test Conditions Min Typ Max Unit DC PERFORMANCE 12 N Resolution Bits DNL Differential Nonlinearity (Notes 1 & 3) 0.4 +1.0 LSB INL Integral Nonlinearity (Notes 1 & 3) 1 +12 LSB STATIC ACCURACY GE Gain Error +0.5 % of FS OE Offset Error 25 mV POWER REQUIREMENTS Supply Voltage 0.9 VREFIN Reference Voltage 0 IDD Supply Current VDD 400 Full Scale at VDD=1.2 Output Voltage Range VOSC Short Circuit Current 1.32 V VDD V 900 µA 17k REFIN Reference Input Resistance OUTPUT CHARACTERISTICS Vout 1.2 (Note 3) 0 4 Ω VDD V 13 mA AC ELECTRICAL CHARACTERISTICS (Specification: VDD=1.2V, REFIN=1.15v,Temp=25°C, unless otherwise specified) Symbol Parameter SR Slew Rate Ts Settling Time Fs Conversion Speed Td Analog output Delay Note 1: Note 2: Note 3: Note 4: Note 5: Rev A0.2 Test Conditions Min Typ 4 (Note 5) (Note 4) Max Unit 2 V/µ sµs 500 ksps 150 ns Linearity is defined from code 127 to 3970 (ICM7722) Guaranteed by design; not tested in production See Applications Information Output delay measured from the 50% point of the rising edge of input data to the full scale transition Settling time measured from the 50% point of full scale transition to the output remaining within 1/2LSB. ICmic reserves the right to change specifications without prior notice 3 ICM7722 TIMING CHARACTERISTICS (VDD = 0.9V to 1.32v, all specifications TMIN to TMAX unless otherwise noted) Symbol Parameter Test Conditions Min Typ Max Unit SCK Cycle Time Data Setup Time (Note 2) 30 ns t2 (Note 2) 10 ns t3 Data Hold Time (Note 2) 10 ns t4 SCK Falling edge to CS Rising Edge (Note 2) 0 ns t5 CS Falling Edge to SCK Rising Edge (Note 2) 10 ns t6 CS Pulse Width (Note 2) 20 ns t1 TIMING DIAGRAM Clk 50% Td Vout 50% 0000..0000 1111..1111 Data 0.5LSB Vout Ts Rev A0.2 ICmic reserves the right to change specifications without prior notice 4 ICM7722 SERIAL INTERFACE TIMING AND OPERATION DIAGRAM t5 t1 t4 t6 CS SCK SDI C3 t2 C2 C1 D0 t3 MSB LSB Figure 1. Serial Interface Timing Diagram CS (UPDATE OUTPUT) (ENABLE SCK) SCK 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 SDI C3 C2 C1 C0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 MSB D0 LSB Figure 2. Serial Interface Operation Diagram CONTENTS OF INPUT SHIFT REGISTER DEVICE CONTROL WORD DATA WORD MSB ICM7722 C3 LSB C2 C1 C0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 Figure 3. Contents of Input Shift Register Rev A0.2 ICmic reserves the right to change specifications without prior notice 5 ICM7722 FUNCTION 0 DATA (D11-D0) Data A 0 1 Data B Input Register transparent, data shifted to DAC register directly, VOB updated 0 0 Data A Data Shifted to Input Register, VOA unchanged 1 0 0 0 1 0 Data Data B A Data Shifted to Input Register, VOB unchanged Data Shifted from Input Register to DAC register, VOA updated 1 1 0 1 0 0 1 0 Data Data B All Data Shifted from Input Register to DAC register, VOB updated Input Registers transparent, data shifted to DAC register directly, All VOUT updated 1 1 1 1 0 1 1 0 Data Data All All Data Shifted to Input Registers, All VOUT unchanged Data Shifted from Input Registers to DAC registers, All VOUT updated C3 C2 C1 C0 0 0 0 0 0 0 1 0 1 DAC FUNCTION Input Register transparent, data shifted to DAC register directly, VOA updated Table 1. Serial Interface Input Word C3 C2 C1 C0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D11~ D5 X X X X D4 D3 D2 D1 D0 DAC FUNCTION 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 1 0 1 A A B B DAC O/P, wakeup Floating Output DAC O/P, wakeup Floating Output Table 2 Shutdown Mode Logic DETAILED DESCRIPTION capacitance. The ICM7722 is a 12-bit rail-to-rail voltage output Dual DAC. This device has a 16-bit input shift register and the DAC has a double-buffered digital input. This DAC has a guaranteed monotonic behavior and the operating supply range is from 0.9v to 1.32v. The output amplifier has a full-scale typical settling time of 2 µs and it dissipates about 400 µA with a 1.2V supply voltage. Serial Interface and Input Logic Reference Input REFIN of ICM7722 has a typical resistance value of 17 kΩ. The reference input accepts positive DC and AC signals that swing from GND to VDD. The voltage at REFIN sets the full-scale output voltage of both the DACs. To determine the output voltage for any code, use the following equation. VOUT = VREF x (D / (2n)) Where D is the numeric value of DAC’s decimal input code, VREF is the reference voltage and n is number of bits, i.e. 12 for ICM7722. This Dual DAC uses a standard 3-wire connection compatible with SPI/QSP and Micro wire interfaces. Data is always loaded in a 16bit word format which consists of 4 control bits (MSBs) followed by 12 bits of data (see Figure 3). Serial Data Input SDI (Serial Data Input) pin is the data input pin for both the DACs. Data is clocked in on the falling edge of SCK that has a Schmitt trigger internally to allow for noise immunity on the SCK pin. This specially eases the use for optocoupled interfaces. Output Buffer Amplifier Dual DAC has two amplifiers with a wide output voltage swing. The actual swing of the output amplifier will be limited by offset error and gain error. See the Applications Information Section for a more detailed discussion. The output amplifier can drive a load of 2.0 KΩ to VDD or GND in parallel with a 500 pF load Rev A0.2 The Chip Select pin, which is the 3rd pin of 8 Lead TSSOP package, is active low. This pin frames the input data for synchronous loading and must be low when data is being clocked into the part. There is an onboard counter on the clock input and after the 16th clock pulse the data is automatically transferred to a 16-bit input latch and the 4 bit control word (C3~C0) is then decoded and the ICmic reserves the right to change specifications without prior notice 6 ICM7722 appropriate command is performed depending on the control word (see Table 1). Chip Select pin must be pulled high (leveltriggered) and back low for the next data word to be loaded in. This pin also disables the SCK pin internally when pulled high. Power-Down Mode The power down mode can be done with loading the control word 1111 (C0 to C3), while the data bits D4 to D0 are to select between the two DACs. See Table 1 and Table 2 for details of operation of this function. Power-On Reset There is a power-on reset on board that will clear the contents of all the latches to all 0s on power-up and the DAC voltage output will go to ground. Rev A0.2 ICmic reserves the right to change specifications without prior notice 7 ICM7722 APPLICATIONS INFORMATION Power Supply Bypassing and Layout Considerations As in any precision circuit, careful consideration has to be given to layout of the supply and ground. The return path from the GND to the supply ground should be short with low impedance. Using a ground plane would be ideal. The supply should have some bypassing on it. A 10 µF tantalum capacitor in parallel with a 0.1 µF ceramic with a low ESR can be used. Ideally these would be placed as close as possible to the device. Avoid crossing digital and analog signals, specially the reference, or running them close to each other. VDD DEADBAND NEGATIVE OFFSET Figure 4. Effect of Negative Offset Output Swing Limitations The ideal rail-to-rail DAC would swing from GND to VDD. However, offset and gain error limit this ability. Figure 4 illustrates how a negative offset error will affect the output. The output will limit close to ground since this is single supply part, resulting in a dead-band area. As a larger input is loaded into the DAC the output will eventually rise above ground. This is why the linearity is specified for a starting code greater than zero. Figure 5 illustrates how a gain error or positive offset error will affect the output when it is close to VDD. A positive gain error or positive offset will cause the output to be limited to the positive supply voltage resulting in a dead-band of codes close to full-scale. Rev A0.2 VDD OFFSET AND GAIN ERROR DEAD BAND POSITIVE OFFSET Figure 5. Effect of Gain Error and Positive Offset ICmic reserves the right to change specifications without prior notice 8 ICM7722 PACKAGE INFORMATION 8 Lead TSSOP Rev A0.2 ICmic reserves the right to change specifications without prior notice 9 ICM7722 PACKAGE INFORMATION ICM77x2 P G Device 2- ICM7722 G = RoHS Compliant Lead-Free package. Blank = Standard package. Non lead-free. Package T = 8-Lead TSSOP Rev A0.2 ICmic reserves the right to change specifications without prior notice 10