MCP4921/4922 12-Bit DAC with SPI™ Interface Features Description • • • • • • • • • • • • • The Microchip Technology Inc. MCP492X are 2.7 – 5.5V, low-power, low DNL, 12-Bit Digital-to-Analog Converters (DACs) with optional 2x buffered output and SPI interface. The MCP492X are DACs that provide high accuracy and low noise performance for industrial applications where calibration or compensation of signals (such as temperature, pressure and humidity) are required. The MCP492X are available in the extended temperature range and PDIP, SOIC, MSOP and TSSOP packages. The MCP492X devices utilize a resistive string architecture, with its inherent advantages of low DNL error, low ratio metric temperature coefficient and fast settling time. These devices are specified over the extended temperature range. The MCP492X include doublebuffered inputs, allowing simultaneous updates using the LDAC pin. These devices also incorporate a Power-On Reset (POR) circuit to ensure reliable power-up. 12-Bit Resolution ±0.2 LSB DNL (typ) ±2 LSB INL (typ) Single or Dual Channel Rail-to-Rail Output SPI™ Interface with 20 MHz Clock Support Simultaneous Latching of the Dual DACs w/LDAC Fast Settling Time of 4.5 µs Selectable Unity or 2x Gain Output 450 kHz Multiplier Mode External VREF Input 2.7V to 5.5V Single-Supply Operation Extended Temperature Range: -40°C to +125°C Applications • • • • • Set Point or Offset Trimming Sensor Calibration Digitally-Controlled Multiplier/Divider Portable Instrumentation (Battery-Powered) Motor Feedback Loop Control Package Types 8-Pin PDIP, SOIC, MSOP Block Diagram SDI SCK LDAC CS 2 Power-on Reset Interface Logic VDD SCK 3 SDI 4 MCP4921 VDD 1 CS 8 VOUTA 7 AVSS 6 VREFA 5 LDAC AVSS 14-Pin PDIP, SOIC, TSSOP Input Input Register A Register B DACB Register VREF String DACA Gain Logic B String DACB Gain Logic Output Op Amps 13 VREFA SCK 4 SDI 5 Buffer Buffer NC 2 CS 3 VREF A 14 VOUTA MCP4922 DACA Register VDD 1 12 AVSS 11 VREFB 10 VOUTB NC 6 9 SHDN NC 7 8 LDAC Output Logic VOUTA SHDN © 2007 Microchip Technology Inc. VOUTB DS21897B-page 1 MCP4921/4922 1.0 ELECTRICAL CHARACTERISTICS Absolute Maximum Ratings † VDD ............................................................................................................. 6.5V † Notice: Stresses above those listed under “Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability. All inputs and outputs w.r.t ............. AVSS –0.3V to VDD+0.3V Current at Input Pins ....................................................±2 mA Current at Supply Pins ...............................................±50 mA Current at Output Pins ...............................................±25 mA Storage temperature .....................................-65°C to +150°C Ambient temp. with power applied ................-55°C to +125°C ESD protection on all pins ........... ≥ 4 kV (HBM), ≥ 400V (MM) Maximum Junction Temperature (TJ) . .........................+150°C 5V AC/DC CHARACTERISTICS Electrical Specifications: Unless otherwise indicated, VDD = 5V, AVSS = 0V, VREF = 2.048V, output buffer gain (G) = 2x, RL = 5 kΩ to GND, CL = 100 pF TA = -40 to +85°C. Typical values at +25°C. Parameters Sym Min Typ Max Units Input Voltage VDD 2.7 — 5.5 Input Current - MCP4921 Input Current - MCP4922 IDD — — 175 350 350 700 µA Conditions Power Requirements Hardware Shutdown Current ISHDN — 0.3 2 µA Software Shutdown Current ISHDN_SW — 3.3 6 µA Power-on-Reset Threshold VPOR — 2.0 — V Input unbuffered, digital inputs grounded, output unloaded, code at 0x000 DC Accuracy Resolution n 12 — — Bits INL Error INL -12 2 12 LSB DNL DNL -0.75 ±0.2 +0.75 Offset Error VOS — ±0.02 1 Device is Monotonic — 0.16 — ppm/°C -45°C to 25°C — -0.44 — ppm/°C +25°C to 85°C gE — -0.10 1 ΔG/°C — -3 — ppm/°C Input Range - Buffered Mode VREF 0.040 — VDD – 0.040 V Input Range - Unbuffered Mode VREF 0 — VDD V Input Impedance RVREF — 165 — kΩ Input Capacitance Unbuffered Mode CVREF — 7 — pF Multiplier Mode -3 dB Bandwidth fVREF — 450 — kHz VREF = 2.5V ±0.2Vp-p, Unbuffered, G=1 fVREF — 400 — kHz VREF = 2.5V ±0.2 Vp-p, Unbuffered, G=2 THDVREF — -73 — dB VREF = 2.5V ±0.2Vp-p, Frequency = 1 kHz Offset Error Temperature Coefficient Gain Error Gain Error Temperature Coefficient VOS/°C LSB % of FSR Code 0x000h % of FSR Code 0xFFFh, not including offset error. Input Amplifier (VREF Input) Multiplier Mode Total Harmonic Distortion Note 1: 2: Note 1 Code = 2048 VREF = 0.2v p-p, f = 100 Hz and 1 kHz Unbuffered Mode By design, not production tested. Too small to quantify. DS21897B-page 2 © 2007 Microchip Technology Inc. MCP4921/4922 5V AC/DC CHARACTERISTICS (CONTINUED) Electrical Specifications: Unless otherwise indicated, VDD = 5V, AVSS = 0V, VREF = 2.048V, output buffer gain (G) = 2x, RL = 5 kΩ to GND, CL = 100 pF TA = -40 to +85°C. Typical values at +25°C. Parameters Sym Min Typ Max Units Conditions Output Swing VOUT — 0.010 to VDD – 0.040 — Phase Margin θm — 66 — degrees Slew Rate SR — 0.55 — V/µs Short Circuit Current ISC — 15 24 mA tsettling — 4.5 — µs DAC-to-DAC Crosstalk — 10 — nV-s Note 2 Major Code Transition Glitch — 45 — nV-s 1 LSB change around major carry (0111...1111 to 1000...0000) Digital Feedthrough — 10 — nV-s Note 2 Analog Crosstalk — 10 — nV-s Note 2 Output Amplifier Settling Time Accuracy is better than 1 LSB for VOUT = 10 mV to (VDD – 40 mV) Within 1/2 LSB of final value from 1/4 to 3/4 full-scale range Dynamic Performance Note 1: 2: By design, not production tested. Too small to quantify. 3V AC/DC CHARACTERISTICS Electrical Specifications: Unless otherwise indicated, VDD = 3V, AVSS = 0V, VREF = 2.048V external, output buffer gain (G) = 1x, RL = 5 kΩ to GND, CL = 100 pF TA = -40 to +85°C. Typical values at 25°C Parameters Sym Min Typ Max Units Input Voltage VDD 2.7 — 5.5 Input Current - MCP4921 Input Current - MCP4922 IDD — — 125 250 250 500 µA Conditions Power Requirements Hardware Shutdown Current ISHDN — 0.25 2 µA Software Shutdown Current ISHDN_SW — 2 6 µA Power-On Reset threshold VPOR — 2.0 — V Input unbuffered, digital inputs grounded, output unloaded, code at 0x000 DC Accuracy Resolution n 12 — — Bits INL Error INL -12 ±3 +12 LSB DNL DNL -0.75 ±0.3 +0.75 LSB VOS — ±0.02 1 % of FSR Code 0x000h VOS/°C — 0.5 — ppm/°C -45°C to 25°C — -0.77 — ppm/°C gE — -0.15 1 % of FSR ΔG/°C — -3 — ppm/°C Input Range - Buffered Mode VREF 0.040 — VDD-0.040 V Input Range - Unbuffered Mode VREF 0 — VDD V Input Impedance RVREF — 165 — kΩ Offset Error Offset Error Temperature Coefficient Gain Error Gain Error Temperature Coefficient Device is Monotonic +25°C to 85°C Code 0xFFFh, not including offset error. Input Amplifier (VREF Input) Note 1: 2: Note 1 Code = 2048, VREF = 0.2v p-p, f = 100 Hz and 1 kHz Unbuffered Mode By design, not production tested. Too small to quantify. © 2007 Microchip Technology Inc. DS21897B-page 3 MCP4921/4922 3V AC/DC CHARACTERISTICS (CONTINUED) Electrical Specifications: Unless otherwise indicated, VDD = 3V, AVSS = 0V, VREF = 2.048V external, output buffer gain (G) = 1x, RL = 5 kΩ to GND, CL = 100 pF TA = -40 to +85°C. Typical values at 25°C Parameters Sym Min Typ Max Units Input Capacitance – Unbuffered Mode CVREF — 7 — pF Multiplier Mode -3 dB Bandwidth fVREF — 440 — kHz VREF = 2.048V ±0.1 Vp-p, unbuffered, G=1 fVREF — 390 — kHz VREF = 2.048V ±0.1 Vp-p, unbuffered, G=2 THDVREF — -73 — dB VREF = 2.5V ±0.1 Vp-p, Frequency = 1 kHz Output Swing VOUT — 0.010 to VDD – 0.040 — Multiplier Mode – Total Harmonic Distortion Conditions Output Amplifier Accuracy is better than 1 LSB for VOUT = 10 mV to (VDD – 40 mV) Phase Margin θm — 66 — degrees Slew Rate SR — 0.55 — V/µs Short Circuit Current ISC — 14 24 mA tsettling — 4.5 — µs DAC-to-DAC Crosstalk — 10 — nV-s Note 2 Major Code Transition Glitch — 45 — nV-s 1 LSB change around major carry (0111...1111 to 1000...0000) Digital Feedthrough — 10 — nV-s Note 2 Analog Crosstalk — 10 — nV-s Note 2 Settling Time Within 1/2 LSB of final value from 1/4 to 3/4 full-scale range Dynamic Performance Note 1: 2: By design, not production tested. Too small to quantify. 5V EXTENDED TEMPERATURE SPECIFICATIONS Electrical Specifications: Unless otherwise indicated, VDD = 5V, AVSS = 0V, VREF = 2.048V, output buffer gain (G) = 2x, RL = 5 kΩ to GND, CL = 100 pF. Typical values at +125°C by characterization or simulation. Parameters Sym Min Typ Max Units Input Voltage VDD 2.7 — 5.5 Input Current - MCP4921 Input Current - MCP4922 IDD — — 200 400 — — µA Hardware Shutdown Current ISHDN — 1.5 — µA Software Shutdown Current ISHDN_SW — 5 — µA Power-On Reset threshold VPOR — 1.85 — V Conditions Power Requirements Input unbuffered, digital inputs grounded, output unloaded, code at 0x000 DC Accuracy Resolution n 12 — — Bits INL Error INL — ±4 — LSB DNL DNL — ±0.25 — LSB VOS — ±0.02 — % of FSR VOS/°C — -5 — ppm/°C Offset Error Offset Error Temperature Coefficient Note 1: 2: Device is Monotonic Code 0x000h +25°C to +125°C By design, not production tested. Too small to quantify. DS21897B-page 4 © 2007 Microchip Technology Inc. MCP4921/4922 5V EXTENDED TEMPERATURE SPECIFICATIONS (CONTINUED) Electrical Specifications: Unless otherwise indicated, VDD = 5V, AVSS = 0V, VREF = 2.048V, output buffer gain (G) = 2x, RL = 5 kΩ to GND, CL = 100 pF. Typical values at +125°C by characterization or simulation. Parameters Sym Min Typ Max Units gE — -0.10 — % of FSR ΔG/°C — -3 — ppm/°C Input Range - Buffered Mode VREF — 0.040 to VDD0.040 — V Input Range - Unbuffered Mode VREF 0 — VDD V Input Impedance RVREF — 174 — kΩ Input Capacitance Unbuffered Mode CVREF — 7 — pF Multiplying Mode -3 dB Bandwidth fVREF — 450 — kHz VREF = 2.5V ±0.1 Vp-p, Unbuffered, G=1 fVREF — 400 — kHz VREF = 2.5V ±0.1 Vp-p, Unbuffered, G=2 THDVREF — — — dB VREF = 2.5V ±0.1Vp-p, Frequency = 1 kHz Output Swing VOUT — — Phase Margin θm 0.010 to VDD – 0.040 — 66 — degrees Slew Rate SR — 0.55 — V/µs Short Circuit Current ISC — 17 — mA tsettling — 4.5 — µs DAC to DAC Crosstalk — 10 — nV-s Note 2 Major Code Transition Glitch — 45 — nV-s 1 LSB change around major carry (0111...1111 to 1000...0000) Digital Feedthrough — 10 — nV-s Note 2 Analog Crosstalk — 10 — nV-s Note 2 Gain Error Gain Error Temperature Coefficient Conditions Code 0xFFFh, not including offset error Input Amplifier (VREF Input) Multiplying Mode - Total Harmonic Distortion Note 1 Code = 2048, VREF = 0.2v p-p, f = 100 Hz and 1 kHz Unbuffered Mode Output Amplifier Settling Time Accuracy is better than 1 LSB for VOUT = 10 mV to (VDD – 40 mV) Within 1/2 LSB of final value from 1/4 to 3/4 full-scale range Dynamic Performance Note 1: 2: By design, not production tested. Too small to quantify. © 2007 Microchip Technology Inc. DS21897B-page 5 MCP4921/4922 AC CHARACTERISTICS (SPI TIMING SPECIFICATIONS) Electrical Specifications: Unless otherwise indicated, VDD= 2.7V – 5.5V, TA= -40 to +125°C. Typical values are at +25°C. Parameters Sym Min Typ Max Units Schmitt Trigger High-Level Input Voltage (All digital input pins) VIH 0.7 VDD — — V Schmitt Trigger Low-Level Input Voltage (All digital input pins) VIL — — 0.2 VD V Conditions D VHYS — 0.05 VDD — Input Leakage Current ILEAKAGE -1 — 1 μA SHDN = LDAC = CS = SDI = SCK + VREF = VDD or AVSS Digital Pin Capacitance (All inputs/outputs) CIN, COUT — 10 — pF VDD = 5.0V, TA = +25°C, fcLK = 1 MHz (Note 1) Clock Frequency FCLK — — 20 MHz Clock High Time tHI 15 — — ns Note 1 tLO 15 — — ns Note 1 tCSSR 40 — — ns Applies only when CS falls with CLK high. (Note 1) tSU 15 — — ns Note 1 Data Input Hold Time tHD 10 — — ns Note 1 SCK Rise to CS Rise Hold Time tCHS 15 — — ns Note 1 CS High Time tCSH 15 — — ns Note 1 LDAC Pulse Width tLD 100 — — ns Note 1 LDAC Setup Time tLS 40 — — ns Note 1 tIDLE 40 — — ns Note 1 Hysteresis of Schmitt Trigger Inputs Clock Low Time CS Fall to First Rising CLK Edge Data Input Setup Time SCK Idle Time before CS Fall Note 1: TA = +25°C (Note 1) By design and characterization, not production tested. tCSH CS tIDLE tCSSR Mode 1,1 tHI tLO tCHS SCK Mode 0,0 tSU tHD SI MSB in LSB in LDAC tLS FIGURE 1-1: DS21897B-page 6 tLD SPI™ Input Timing. © 2007 Microchip Technology Inc. MCP4921/4922 TEMPERATURE CHARACTERISTICS Electrical Specifications: Unless otherwise indicated, VDD = +2.7V to +5.5V, AVSS = GND. Parameters Sym Min Typ Max Units Specified Temperature Range TA -40 — +125 °C Operating Temperature Range TA -40 — +125 °C Storage Temperature Range TA -65 — +150 °C Thermal Resistance, 8L-PDIP θJA — 85 — °C/W Thermal Resistance, 8L-SOIC θJA — 163 — °C/W Thermal Resistance, 8L-MSOP θJA — 206 — °C/W Thermal Resistance, 14L-PDIP θJA — 70 — °C/W Thermal Resistance, 14L-SOIC θJA — 120 — °C/W Thermal Resistance, 14L-TSSOP θJA — 100 — °C/W Conditions Temperature Ranges Note 1 Thermal Package Resistances Note 1: The MCP492X family of DACs operate over this extended temperature range, but with reduced performance. Operation in this range must not cause TJ to exceed the Maximum Junction Temperature of 150°C. © 2007 Microchip Technology Inc. DS21897B-page 7 MCP4921/4922 2.0 TYPICAL PERFORMANCE CURVES Note: The graphs and tables provided following this note are a statistical summary based on a limited number of samples and are provided for informational purposes only. The performance characteristics listed herein are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified operating range (e.g., outside specified power supply range) and therefore outside the warranted range. Note: Unless otherwise indicated, TA = +25°C, VDD = 5V , AVSS = 0V, VREF = 2.048V, Gain = 2, RL = 5 kΩ, CL = 100 pF. 0.3 0.0766 Absolute DNL (LSB) DNL (LSB) 0.2 0.1 0 -0.1 -0.2 0.0764 0.0762 0.076 0.0758 0.0756 0.0754 0.0752 0.075 -0.3 0 1024 2048 3072 -40 4096 FIGURE 2-4: Temperature. DNL vs. Code. 20 40 60 80 100 120 Absolute DNL vs. Ambient 0.35 Absolute DNL (LSB) 0.2 0.1 DNL (LSB) 0 Ambient Temperature (ºC) Code (Decimal) FIGURE 2-1: -20 0 -0.1 0.3 0.25 0.2 0.15 0.1 0.05 0 -0.2 0 1024 2048 3072 Code (Decimal) FIGURE 2-2: Temperature. 125C 4096 85C 1 3 4 5 Voltage Reference (V) 25C DNL vs. Code and Ambient 2 FIGURE 2-5: Reference. Absolute DNL vs. Voltage 0.4 0.3 DNL (LSB) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 0 1024 2048 Code (Decimal) FIGURE 2-3: Gain=1. DS21897B-page 8 3072 1 2 4096 3 4 5.5 DNL vs. Code and VREF. © 2007 Microchip Technology Inc. MCP4921/4922 5 4 3 2 1 0 -1 -2 -3 -4 -5 3 Ambient Temperature 125C 85 VREF 2 25 1 3 4 5.5 0 -1 -2 -3 -4 0 1024 2048 3072 4096 0 1024 Code (Decimal) FIGURE 2-6: Temperature. INL vs. Code and Ambient FIGURE 2-9: 2048 3072 Code (Decimal) 4096 INL vs. Code and VREF. 2 2.5 2 0 INL (LSB) Absolute INL (LSB) 2 1 INL (LSB) INL (LSB) Note: Unless otherwise indicated, TA = +25°C, VDD = 5V , AVSS = 0V, VREF = 2.048V, Gain = 2, RL = 5 kΩ, CL = 100 pF. 1.5 1 -2 -4 0.5 -6 0 -40 -20 0 20 40 60 80 100 0 120 1024 FIGURE 2-7: Temperature. 2048 3072 4096 Code (Decimal) Ambient Temperature (ºC) Absolute INL vs. Ambient FIGURE 2-10: Note: INL vs. Code. Single device graph (Figure 2-10) for illustration of 64 code effect. Absolute INL (LSB) 3 2.5 2 1.5 1 0.5 0 1 2 3 4 5 Voltage Reference (V) FIGURE 2-8: Absolute INL vs. VREF. © 2007 Microchip Technology Inc. DS21897B-page 9 MCP4921/4922 Note: Unless otherwise indicated, TA = +25°C, VDD = 5V, AVSS = 0V, VREF = 2.048V, Gain = 2. 210 400 5.5V 5.5V 5.0V 4.0V 3.0V 2.7V 5.0V 4.0V 3.0V 2.7V 170 VDD 150 350 IDD (µA) 250 130 110 200 0 20 40 60 80 100 120 Ambient Temperature (°C) IDD (μA) MCP4921 IDD Histogram IDD (μA) 9 16 8 14 7 12 6 5 4 3 MCP4922 IDD Histogram FIGURE 2-15: (VDD = 2.7V). Occurrence 10 8 6 4 2 2 1 DS21897B-page 10 MCP4921 IDD Histogram 415 400 385 370 355 340 325 310 295 IDD (μA) IDD (μA) FIGURE 2-13: (VDD = 5.0V). 280 151 156 161 166 171 176 181 186 191 196 201 265 0 0 250 Occurrence FIGURE 2-12: (VDD = 2.7V). 325 215 167 165 163 161 159 157 155 153 151 149 147 145 143 0 315 2 305 4 295 6 285 8 275 Occurrence 14 20 18 16 14 12 10 8 6 4 2 0 265 16 10 0 20 40 60 80 100 120 Ambient Temperature (ºC) FIGURE 2-14: MCP4922 IDD vs. Ambient Temperature and VDD. 18 12 -20 255 FIGURE 2-11: MCP4921 IDD vs. Ambient Temperature and VDD. -40 245 -20 235 -40 Occurrence VDD 300 225 IDD (µA) 190 FIGURE 2-16: (VDD = 5.0V). MCP4922 IDD Histogram © 2007 Microchip Technology Inc. MCP4921/4922 Note: Unless otherwise indicated, TA = +25°C, VDD = 5V , AVSS = 0V, VREF = 2.048V, Gain = 2, RL = 5 kΩ, CL = 100 pF. 2 -0.08 VDD 5.5V 5.0V 4.0V 1 3.0V 2.7V 0.5 5.5V Gain Error (%) ISHDN (μA) 1.5 VDD -0.1 5.0V -0.12 4.0V 3.0V 2.7V -0.14 -0.16 0 -40 -20 -40 0 20 40 60 80 100 120 Ambient Temperature (ºC) FIGURE 2-17: Hardware Shutdown Current vs. Ambient Temperature and VDD. -20 0 20 40 60 80 100 120 Ambient Temperature (ºC) FIGURE 2-20: Gain Error vs. Ambient Temperature and VDD. 6 VDD 4 5.5V 5.0V 4 4.0V 3 3.0V 2.7V 2 VDD 1 VIN Hi Threshold (V) ISHDN_SW (μA) 5 0 5.0V 3 2.5 4.0V 2 3.0V 2.7V 1.5 1 -40 -20 0 20 40 60 80 100 120 Ambient Temperature (ºC) -40 FIGURE 2-18: Software Shutdown Current vs. Ambient Temperature and VDD. -20 0 20 40 60 80 100 120 Ambient Temperature (ºC) FIGURE 2-21: VIN High Threshold vs Ambient Temperature and VDD. 0.12 0.08 VDD 0.06 0.04 5.5V 0.02 0 5.0V 4.0V 3.0V 2.7V -0.02 -40 -20 0 20 40 60 80 100 120 Ambient Temperature (ºC) FIGURE 2-19: Offset Error vs. Ambient Temperature and VDD. © 2007 Microchip Technology Inc. VIN Low Threshold (V) 1.6 0.1 Offset Error (%) 5.5V 3.5 VDD 1.5 5.5V 1.4 5.0V 1.3 1.2 4.0V 1.1 1 3.0V 2.7V 0.9 0.8 -40 -20 0 20 40 60 80 100 120 Ambient Temperature (ºC) FIGURE 2-22: VIN Low Threshold vs Ambient Temperature and VDD. DS21897B-page 11 MCP4921/4922 VDD 5.5V 5.0V 4.0V 3.0V 2.7V 0.0045 VOUT_LOW Limit (Y-AVSS)(V) 2.5 2.25 2 1.75 1.5 1.25 1 0.75 0.5 0.25 0 0.004 5.5V 0.0035 0.003 5.0V 0.0025 4.0V 3.0V 2.7V 0.002 -40 -20 0 20 40 60 80 100 120 Ambient Temperature (ºC) 0 20 40 60 80 100 120 Ambient Temperature (ºC) FIGURE 2-23: Input Hysteresis vs. Ambient Temperature and VDD. FIGURE 2-26: VOUT Low Limit vs. Ambient Temperature and VDD. 18 175 VREF_UNBUFFERED Impedance (kOhm) 5.5V 2.7V VDD 170 165 160 VDD 17 5.5V 5.0V 4.0V 3.0V 2.7V 16 15 14 13 12 11 10 155 -40 -20 -40 0 20 40 60 80 100 120 Ambient Temperature (ºC) FIGURE 2-24: VREF Input Impedance vs. Ambient Temperature and VDD. 0.045 5.0 0.035 VREF=4.0 4.0V 0.03 0.025 3.0V 2.7V 0.02 VDD 0.015 0.01 0 20 40 60 80 100 120 Ambient Temperature (ºC) 6.0 5.5V 5.0V 0.04 -20 FIGURE 2-27: IOUT High Short vs. Ambient Temperature and VDD. VOUT (V) VOUT_HI Limit (VDD-Y)(V) VDD 0.0015 -40 -20 IOUT_HI_SHORTED (mA) VIN_SPI Hysteresis (V) Note: Unless otherwise indicated, TA = +25°C, VDD = 5V , AVSS = 0V, VREF = 2.048V, Gain = 2, RL = 5 kΩ, CL = 100 pF. 4.0 Output Shorted to VDD 3.0 2.0 1.0 Output Shorted to VSS 0.005 0.0 0 -40 -20 0 20 40 60 80 100 120 Ambient Temperature (ºC) FIGURE 2-25: VOUT High Limit vs. Ambient Temperature and VDD. DS21897B-page 12 0 2 FIGURE 2-28: 4 6 8 10 IOUT (mA) 12 14 16 IOUT vs VOUT. Gain = 1. © 2007 Microchip Technology Inc. MCP4921/4922 Note: Unless otherwise indicated, TA = +25°C, VDD = 5V , AVSS = 0V, VREF = 2.048V, Gain = 2, RL = 5 kΩ, CL = 100 pF. VOUT VOUT SCK LDAC LDAC Time (1 µs/div) FIGURE 2-29: VOUT Rise Time 100%. Time (1 µs/div) FIGURE 2-32: VOUT Rise Time 25% - 75% VOUT VOUT SCK SCK LDAC LDAC Time (1 µs/div) VOUT Fall Time. FIGURE 2-33: Shutdown. VOUT SCK LDAC Time (1 µs/div) FIGURE 2-31: VOUT Rise Time Exit Ripple Rejection (dB) FIGURE 2-30: Time (1 µs/div) VOUT Rise Time 50%. © 2007 Microchip Technology Inc. Frequency (Hz) FIGURE 2-34: PSRR vs. Frequency. DS21897B-page 13 MCP4921/4922 Note: Unless otherwise indicated, TA = +25°C, VDD = 5V , AVSS = 0V, VREF = 2.50V, Gain = 2, RL = 5 kΩ, CL = 100 pF. 0 Attenuation (dB) -2 -4 -6 -8 -10 -12 100 Frequency (kHz) FIGURE 2-35: 160 416 672 928 1184 1440 1696 1952 2208 2464 2720 2976 3232 3488 3744 1,000 Multiplier Mode Bandwidth. D= D= D= D= D= D= D= D= D= D= D= D= D= D= D= -45 qVREF – qVOUT D= D= D= D= D= D= D= D= D= D= D= D= D= D= D= 0 -90 -135 -180 100 FIGURE 2-37: Frequency (kHz) 160 416 672 928 1184 1440 1696 1952 2208 2464 2720 2976 3232 3488 3744 1,000 Phase Shift. Bandwidth (kHz) Figure 2-35 calculation: Attenuation (dB) = 20 log (VOUT/VREF) – 20 log (G(D/4096)) 600 580 560 540 520 500 480 460 440 420 400 G=1 G=2 44 37 88 34 32 32 76 29 20 27 64 24 08 22 52 19 96 16 40 14 84 11 8 92 2 67 6 41 0 16 Worst Case Codes (decimal) FIGURE 2-36: Codes. DS21897B-page 14 -3 db Bandwidth vs. Worst © 2007 Microchip Technology Inc. MCP4921/4922 3.0 PIN DESCRIPTIONS The descriptions of the pins are listed in Table 3-1. TABLE 3-1: PIN FUNCTION TABLE MCP4921 Pin No. MCP4922 Pin No. Symbol 1 1 VDD — 2 NC No Connection 2 3 CS Chip Select Input 3 4 SCK Serial Clock Input 4 5 SDI Serial Data Input — 6 NC No Connection — 7 NC No Connection 5 8 LDAC Syncronization input used to transfer DAC settings from serial latches to the output latches. 3.1 Function Positive Power Supply Input (2.7V to 5.5V) — 9 SHDN Hardware Shutdown Input — 10 VOUTB DACB Output — 11 VREFB DACB Voltage Input (AVSS to VDD) 7 12 AVSS Analog ground 6 13 VREFA DACA Voltage Input (AVSS to VDD) 8 14 VOUTA DACA Output Positive Power Supply Input (VDD) VDD is the positive power supply input. The input power supply is relative to AVSS and can range from 2.7V to 5.5V. A decoupling capacitor on VDD is recommended to achieve maximum performance. 3.6 SHDN is the hardware shutdown input that requires an active-low input signal to configure the DACs in their low-power Standby mode. 3.7 3.2 Chip Select (CS) CS is the chip select input, which requires an active-low signal to enable serial clock and data functions. Serial Clock Input (SCK) SCK is the SPI compatible serial clock input. 3.4 Serial Data Input (SDI) SDI is the SPI compatible serial data input. 3.5 Latch DAC Input (LDAC) LDAC (the latch DAC syncronization input) transfers the input latch registers to the DAC registers (output latches) when low. Can also be tied low if transfer on the rising edge of CS is desired. © 2007 Microchip Technology Inc. DACx Outputs (VOUTA, VOUTB) VOUTA and VOUTB are DAC outputs. The DAC output amplifier drives these pins with a range of AVSS to VDD. 3.8 3.3 Hardware Shutdown Input (SHDN) DACX Voltage Reference Inputs (VREFA, VREFB) VREFA and VREFB are DAC voltage reference inputs. The analog signal on these pins is utilized to set the reference voltage on the string DAC. The input signal can range from AVSS to VDD. 3.9 Analog Ground (AVSS) AVSS is the analog ground pin. DS21897B-page 15 MCP4921/4922 4.0 GENERAL OVERVIEW The MCP492X devices are voltage output string DACs. These devices include input amplifiers, rail-to-rail output amplifiers, reference buffers, shutdown and resetmanagement circuitry. Serial communication conforms to the SPI protocol. The MCP492X operates from 2.7V to 5.5V supplies. The coding of these devices is straight binary and the ideal output voltage is given by Equation 4-1, where G is the selected gain (1x or 2x), DN represents the digital input value and n represents the number of bits of resolution (n = 12). EQUATION 4-1: INL < 0 111 110 101 Digital Input Code VREF, GAIN MCP492X MCP492X 4.0.1 External VREF, 1x External VREF, 2x Ideal transfer function 000 INL < 0 1 LSB is the ideal voltage difference between two successive codes. Table 4-1 illustrates how to calculate LSB. Device 011 001 V REF GD N VOUT = ------------------------n 2 LSB SIZES 100 010 LSB SIZE TABLE 4-1: Actual transfer function LSB SIZE VREF/4096 2 VREF/4096 DAC Output FIGURE 4-1: 4.0.2 INL Accuracy. DNL ACCURACY DNL error is the measure of variations in code widths from the ideal code width. A DNL error of zero would imply that every code is exactly 1 LSB wide. INL ACCURACY INL error for these devices is the maximum deviation between an actual code transition point and its corresponding ideal transition point once offset and gain errors have been removed. These endpoints are from 0x000 to 0xFFF. Refer to Figure 4-1. Positive INL means transition(s) later than ideal. Negative INL means transition(s) earlier than ideal. 111 110 101 Digital Input Code Actual transfer function 100 Ideal transfer function 011 010 Wide code, > 1 LSB 001 000 Narrow code < 1 LSB DAC Output FIGURE 4-2: 4.0.3 DNL Accuracy. OFFSET ERROR Offset error is the deviation from zero voltage output when the digital input code is zero. 4.0.4 GAIN ERROR Gain error is the deviation from the ideal output, VREF– 1 LSB, excluding the effects of offset error. DS21897B-page 16 © 2007 Microchip Technology Inc. MCP4921/4922 4.1 4.1.1 Circuit Descriptions OUTPUT AMPLIFIERS The DACs’ outputs are buffered with a low-power, precision CMOS amplifier. This amplifier provides low offset voltage and low noise. The output stage enables the device to operate with output voltages close to the power supply rails. Refer to Section 1.0 “Electrical Characteristics” for range and load conditions. In addition to resistive load driving capability, the amplifier will also drive high capacitive loads without oscillation. The amplifiers’ strong outputs allow VOUT to be used as a programmable voltage reference in a system. If the power supply voltage is less than the POR threshold (VPOR = 2.0V, typical), the DACs will be held in their reset state. They will remain in that state until VDD > VPOR and a subsequent write command is received. Figure 4-3 shows a typical power supply transient pulse and the duration required to cause a reset to occur, as well as the relationship between the duration and trip voltage. A 0.1 µF decoupling capacitor mounted as close as possible to the VDD pin provides additional transient immunity. 5V 4.1.1.1 Supply Voltages Selecting a gain of 2 reduces the bandwidth of the amplifier in Multiplying mode. Refer to Section 1.0 “Electrical Characteristics” for the Multiplying mode bandwidth for given load conditions. Programmable Gain Block The rail-to-rail output amplifier has configurable gain allowing optimal full-scale outputs for differing voltage reference inputs. The output amplifier gain has two selections, a gain of 1 V/V (GA = 1) or a gain of 2 V/V (GA = 0). VOLTAGE REFERENCE AMPLIFIERS The input buffer amplifiers for the MCP492X devices provide low offset voltage and low noise. A configuration bit for each DAC allows the VREF input to bypass the input buffer amplifiers, achieving a Buffered or Unbuffered mode. The default value for this bit is unbuffered. Buffered mode provides a very high input impedance, with only minor limitations on the input range and frequency response. Unbuffered mode provides a wide input range (0V to VDD), with a typical input impedance of 165 kΩ w/7 pF. 4.1.3 POWER-ON RESET CIRCUIT The Power-On Reset (POR) circuit ensures that the DACs power-up with SHDN = 0 (high-impedance). The devices will continue to have a high-impedance output until a valid write command is performed to either of the DAC registers and the LDAC pin meets the input low threshold. © 2007 Microchip Technology Inc. Transient Duration Time Transient Duration (µs) 10 The output range is ideally 0.000V to 4095/4096 * VREF when G = 1, and 0.000 to 4095/4096 * VREF when G = 2. The default value for this bit is a gain of 2, yielding an ideal full-scale output of 0.000V to 4.096V when utilizing a 2.048V VREF. Note that the near rail-to-rail CMOS output buffer’s ability to approach AVSS and VDD establish practical range limitations. The output swing specification in Section 1.0 “Electrical Characteristics” defines the range for a given load condition. 4.1.2 VPOR VDD - VPOR 8 6 4 Transients above the curve will cause a reset 2 0 FIGURE 4-3: 4.1.4 TA = +25°C Transients below the curve will NOT cause a reset 1 2 3 4 VDD – VPOR (V) 5 Typical Transient Response. SHUTDOWN MODE Shutdown mode can be entered by using either hardware or software commands. The hardware pin (SHDN) is only available on the MCP4922. During Shutdown mode, the supply current is isolated from most of the internal circuitry. The serial interface remains active, thus allowing a write command to bring the device out of Shutdown mode. When the output amplifiers are shut down, the feedback resistance (typically 500 kΩ) produces a high-impedance path to AVSS. The device will remain in Shutdown mode until the SHDN pin is brought high and a write command with SD = 1 is latched into the device. When a DAC is changed from Shutdown to Active mode, the output settling time takes < 10 µs, but greater than the standard Active mode settling time (4.5 µs). DS21897B-page 17 MCP4921/4922 5.0 SERIAL INTERFACE 5.1 Overview 5.2 The write command is initiated by driving the CS pin low, followed by clocking the four configuration bits and the 12 data bits into the SDI pin on the rising edge of SCK. The CS pin is then raised, causing the data to be latched into the selected DAC’s input registers. The MCP492X utilizes a double-buffered latch structure to allow both DACA’s and DACB’s outputs to be syncronized with the LDAC pin, if desired. Upon the LDAC pin achieving a low state, the values held in the DAC’s input registers are transferred into the DACs’ output registers. The outputs will transition to the value and held in the DACX register. The MCP492X family is designed to interface directly with the Serial Peripheral Interface (SPI) port, available on many microcontrollers, and supports Mode 0,0 and Mode 1,1. Commands and data are sent to the device via the SDI pin, with data being clocked-in on the rising edge of SCK. The communications are unidirectional and, thus, data cannot be read out of the MCP492X. The CS pin must be held low for the duration of a write command. The write command consists of 16 bits and is used to configure the DAC’s control and data latches. Register 5-1 details the input registers used to configure and load the DACA and DACB registers. Refer to Figure 1-1 and Section 1.0 “Electrical Characteristics” AC Electrical Characteristics table for detailed input and output timing specifications for both Mode 0,0 and Mode 1,1 operation. REGISTER 5-1: Write Command All writes to the MCP492X are 16-bit words. Any clocks past 16 will be ignored. The most significant four bits are configuration bits. The remaining 12 bits are data bits. No data can be transferred into the device with CS high. This transfer will only occur if 16 clocks have been transferred into the device. If the rising edge of CS occurs prior, shifting of data into the input registers will be aborted. WRITE COMMAND REGISTER Upper Half: W-x W-x W-x W-0 W-x W-x W-x W-x A/B BUF GA SHDN D11 D10 D9 D8 bit 15 bit 8 Lower Half: W-x D7 bit 7 bit 15 W-x D6 W-x D5 W-x D4 W-x D3 W-x D2 W-x D1 W-x D0 bit 0 A/B: DACA or DACB Select bit Write to DACB Write to DACA 1= 0= bit 14 BUF: VREF Input Buffer Control bit Buffered Unbuffered 1= 0= bit 13 GA: Output Gain Select bit 1x (VOUT = VREF * D/4096) 2x (VOUT = 2 * VREF * D/4096) 1= 0= bit 12 SHDN: Output Power Down Control bit 1 = Output Power Down Control bit 0 = Output buffer disabled, Output is high impedance bit 11-0 D11:D0: DAC Data bits 12 bit number “D” which sets the output value. Contains a value between 0 and 4095. Legend R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR 1 = bit is set 0 = bit is cleared DS21897B-page 18 x = bit is unknown © 2007 Microchip Technology Inc. MCP4921/4922 CS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 SCK (mode 0,0) config bits SDI (mode 1,1) 12 data bits A/B BUF GA SHDN D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 LDAC VOUT FIGURE 5-1: Write Command. © 2007 Microchip Technology Inc. DS21897B-page 19 MCP4921/4922 At the time of this data sheet’s release, circuit examples had not completed testing. Your results may vary. VDD • • • • • Set Point or Offset Trimming Sensor Calibration Digitally-Controlled Multiplier/Divider Portable Instrumentation (Battery Powered) Motor Feedback Loop Control 6.1 Digital Interface The MCP492X utilizes a 3-wire syncronous serial protocol to transfer the DACs’ setup and output values from the digital source. The serial protocol can be interfaced to SPI™ or Microwire peripherals common on many microcontrollers, including Microchip’s PIC® MCUs & dsPICTM DSC family of microcontrollers. In addition to the three serial connections (CS, SCK and SDI), the LDAC signal syncronizes when the serial settings are latched into the DAC’s output from the serial input latch. Figure 6-1 illustrates the required connections. Note that LDAC is active-low. If desired, this input can be tied low to reduce the required connections from 4 to 3. Write commands will be latched directly into the output latch when a valid 16 clock transmission has been received and CS has been raised. 6.2 Power Supply Considerations The typical application will require a by-pass capacitor in order to filter high-frequency noise. The noise can be induced onto the power supply's traces or as a result of changes on the DAC's output. The bypass capacitor helps to minimize the effect of these noise sources on signal integrity. Figure 6-1 illustrates an appropriate bypass strategy. VDD VREFA VOUTA 0.1 µF VREFB VOUTB CS1 SDI VREFA VOUTA VREFB VOUTB SDI AVSS SDO SCK LDAC CS0 AVSS FIGURE 6-1: Diagram. 6.3 PIC® Microcontroller Applications generally suited for the MCP492X devices include: VDD 0.1 µF 0.1 µF The MCP492X devices are general purpose DACs intended to be used in applications where a precision, low-power DAC with moderate bandwidth is required. MCP492X Note: TYPICAL APPLICATIONS MCP492X 6.0 AVSS Typical Connection Layout Considerations Inductively-coupled AC transients and digital switching noise can degrade the input and output signal integrity, potentially masking the MCP492X’s performance. Careful board layout will minimize these effects and increase the signal-to-noise ratio (SNR). Bench testing has shown that a multi-layer board utilizing a low-inductance ground plane, isolated inputs, isolated outputs and proper decoupling are critical to achieving the performance that the silicon is capable of providing. Particularly harsh environments may require shielding of critical signals. Breadboards and wire-wrapped boards are not recommended if low noise is desired. In this example, the recommended bypass capacitor value is 0.1 µF. This capacitor should be placed as close to the device power pin (VDD) as possible (within 4 mm). The power source supplying these devices should be as clean as possible. If the application circuit has separate digital and analog power supplies, AVDD and AVSS should reside on the analog plane. DS21897B-page 20 © 2007 Microchip Technology Inc. MCP4921/4922 6.4 6.4.1.1 Single-Supply Operation If the output range is reduced relative to AVSS, simply reducing VREF will reduce the magnitude of each output step. If the application is calibrating the threshold of a diode, transistor or resistor tied to AVSS or VREF, a theshold range of 0.8V may be desired to provide 200 µV resolution. Two common methods to achieve a 0.8V range is to either reduce VREF to 0.82V or use a voltage divider on the DAC’s output. If a VREF is available with the desired output value, using that VREF is an option. Occasionally, when using a low-voltage VREF, the noise floor causes SNR error that is intolerable. The voltage divider method provides some advantages when VREF needs to be very low or when the desired output voltage is not available. In this case, a larger value VREF is used while two resistors scale the output range down to the precise desired level. Using a common VREF output has availability and cost advantages. Example 6-1 illustrates this concept. Note that the voltage divider can be connected to AVSS or VREF, depending on the application’s requirements. The MCP492X is a rail-to-rail (R-R) input and output DAC designed to operate with a VDD range of 2.7V to 5.5V. Its output amplifier is robust enough to drive common, small-signal loads directly, thus eliminating the cost and size of an external buffer for most applications. 6.4.1 Decreasing The Output Step Size DC SET POINT OR CALIBRATION A common application for a DAC with the MCP492X’s performance is digitally-controlled set points and/or calibration of variable parameters, such as sensor offset or slope. 12-bit resolution provides 4096 output steps. If a 4.096V VREF is provided, an LSB would represent 1 mV of resolution. If a smaller output step size is desired, the output range would need to be reduced. The MCP492X’s low, ±0.75 (max.) DNL performance is critical to meeting calibration accuracy in production. VDD VCC+ Rsense VREF VDD MCP492X VOUT Comparator R1 Vtrip R2 0.1 uF VCC– SPI™ 3 D V OUT = V REF G ------12 2 R2 V trip = V OUT ⎛ ------------------⎞ ⎝ R1 + R 2⎠ EXAMPLE 6-1: G = Gain select (1x or 2x) D = Digital value of DAC (0 – 4096) Set Point or Threshold Calibration. © 2007 Microchip Technology Inc. DS21897B-page 21 MCP4921/4922 6.4.1.2 Building a “Window” DAC If the threshold is not near VREF or AVSS, then creating a “window” around the threshold has several advantages. One simple method to create this “window” is to use a voltage divider network with a pull-up and pulldown resistor. Example 6-2 and Example 6-4 illustrates this concept. When calibrating a set point or threshold of a sensor, rarely does the sensor utilize the entire output range of the DAC. If the LSB size is adequate to meet the application’s accuracy needs, then the resolution is sacrificed without consequences. If greater accuracy is needed, then the output range will need to be reduced to increase the resolution around the desired threshold. VCC+ VREF The MCP492X’s low, ±0.75 (max.) DNL performance is critical to meet calibration accuracy in production. VCC+ Rsense VDD MCP492X VOUT R3 R1 Comparator Vtrip VCC- 0.1 µF R2 SPI™ 3 VCCD V OUT = V REF G ------12 2 Thevenin Equivalent R 2 R3 R 23 = -----------------R2 + R 3 DS21897B-page 22 R1 VOUT VO ( V CC+ R 2 ) + ( V CC- R 3 ) V 23 = -----------------------------------------------------R 2 + R3 V OUT R23 + V 23 R 1 V trip = -------------------------------------------R 2 + R 23 EXAMPLE 6-2: G = Gain select (1x or 2x) D = Digital value of DAC (0 – 4096) R23 V23 Single-Supply “Window” DAC. © 2007 Microchip Technology Inc. MCP4921/4922 6.5 Bipolar Operation Example 6-3 illustrates a simple bipolar voltage source configuration. R1 and R2 allow the gain to be selected, while R3 and R4 shift the DAC's output to a selected offset. Note that R4 can be tied to VREF, instead of AVSS, if a higher offset is desired. Note that a pull-up to VREF could be used, instead of R4, if a higher offset is desired. Bipolar operation is achievable using the MCP492X by using an external operational amplifier (op amp). This configuration is desirable due to the wide variety and availability of op amps. This allows a general purpose DAC, with its cost and availability advantages, to meet almost any desired output voltage range, power and noise performance. R2 VREF VREF VDD VCC+ R1 VOUT R3 VO VIN+ MCP492X VCC– 0.1 µF R4 SPI™ 3 D VOUT = VREF G ------12 2 V OUT R 4 VIN+ = -------------------R3 + R4 R2 R2 VO = VIN+ ⎛⎝ 1 + ------⎞⎠ – V REF ⎛⎝ ------⎞⎠ R1 R1 EXAMPLE 6-3: 6.5.1 Digitally-Controlled Bipolar Voltage Source. DESIGN A BIPOLAR DAC USING EXAMPLE 6-3 An output step magnitude of 1 mV with an output range of ±2.05V is desired for a particular application. 1. 2. G = Gain select (1x or 2x) D = Digital value of DAC (0 – 4096) Calculate the range: +2.05V – (-2.05V) = 4.1V. Calculate the resolution needed: 4.1V/1 mV = 4100 4. Next, solve for R3 and R4 by setting the DAC to 4096, knowing that the output needs to be +2.05V. R4 2.05V + 0.5V REF 2 ---------------------- = ----------------------------------------= --1.5VREF ( R3 + R 4 ) 3 If R4 = 20 kΩ, then R3 = 10 kΩ Since 212 = 4096, 12-bit resolution is desired. 3. The amplifier gain (R2/R1), multiplied by VREF, must be equal to the desired minimum output to achieve bipolar operation. Since any gain can be realized by choosing resistor values (R1+R2), the VREF source needs to be determined first. If a VREF of 4.1V is used, solve for the gain by setting the DAC to 0, knowing that the output needs to be -2.05V. The equation can be simplified to: – R2 – 2.05 – 2.05 --------- = ------------- = ------------R1 V REF 4.1 R 1 -----2- = --R1 2 If R1 = 20 kΩ and R2 = 10 kΩ, the gain will be 0.5. © 2007 Microchip Technology Inc. DS21897B-page 23 MCP4921/4922 6.6 Selectable Gain and Offset Bipolar Voltage Output Using A Dual DAC This circuit is typically used in Multiplier mode and is ideal for linearizing a sensor whose slope and offset varies. Refer to Section 6.9 “Using Multiplier Mode” for more information on Multiplier mode. In some applications, precision digital control of the output range is desirable. Example 6-4 illustrates how to use the MCP4922 to achieve this in a bipolar or single-supply application. The equation to design a bipolar “window” DAC would be utilized if R3, R4 and R5 are populated. R2 VREFA VDD VOUTA VCC+ R1 MCP492X VDD VREFB DACA (Gain Adjust) MCP492X VOUTB VO R5 R3 DACB (Offset Adjust) SPI™ VCC+ R4 3 0.1uF VCC– VCC– DB VOUTB = ( V REFB G B ) ------12 2 DA V OUTA = ( VREFA G A ) ------12 2 AVSS = GND V OUTB R 4 + VCC- R 3 V IN+ = -----------------------------------------------R 3 + R4 G = Gain select (1x or 2x) R2 R2 VO = V IN+ ⎛⎝ 1 + ------⎞⎠ – V OUTA ⎛⎝ ------⎞⎠ R1 R1 D = Digital value of DAC (0 – 4096) Offset Adjust Gain Adjust Bipolar “Window” DAC using R4 and R5 Thevenin Equivalent V CC+ R 4 + VCC- R5 V45 = -------------------------------------------R 4 + R5 V OUTB R45 + V 45 R 3 V IN+ = ----------------------------------------------R 3 + R 45 R4 R5 R 45 = -----------------R4 + R5 R2 R2 V O = VIN+ ⎛⎝ 1 + ------⎞⎠ – V OUTA ⎛⎝ ------⎞⎠ R1 R1 Offset Adjust Gain Adjust EXAMPLE 6-4: DS21897B-page 24 Bipolar Voltage Source With Selectable Gain and Offset. © 2007 Microchip Technology Inc. MCP4921/4922 6.7 Designing A Double-Precision DAC Using A Dual DAC 1. Example 6-5 illustrates how to design a single-supply voltage output capable of up to 24-bit resolution from a dual 12-bit DAC. This design is simply a voltage divider with a buffered output. As an example, if a similar application to the one developed in Section 6.5.1 “Design a bipolar dac using Example 6-3” required a resolution of 1 µV instead of 1 mV and a range of 0V to 4.1V, then 12-bit resolution would not be adequate. 2. 3. 4. VDD VREF MCP492X VCC+ DACA (Fine Adjust) VO VOUTA VDD MCP492X Calculate the resolution needed: 4.1V/1uV = 4.1e06. Since 222 = 4.2e06, 22-bit resolution is desired. Since DNL = ±0.75 LSB, this design can be attempted with the MCP492X. Since DACB‘s VOUTB has a resolution of 1 mV, its output only needs to be “pulled” 1/1000 to meet the 1 µV target. Dividing VOUTA by 1000 would allow the application to compensate for DACB‘s DNL error. If R2 is 100Ω, then R1 needs to be 100 kΩ. The resulting transfer function is not perfectly linear, as shown in the equation of Example 6-5. R1 R1 >> R2 VOUTB R2 0.1 µF VCC– DACB (Course Adjust) SPI™ 3 DA V OUTA = V REFA G A ------12 2 DB V OUTB = VREFB G B ------12 2 G = Gain select (1x or 2x) D = Digital value of DAC (0 – 4096) VOUTA R 2 + VOUTB R 1 V O = ----------------------------------------------------R 1 + R2 EXAMPLE 6-5: Simple, Double-Precision DAC. © 2007 Microchip Technology Inc. DS21897B-page 25 MCP4921/4922 6.8 Building A Programmable Current Source Example 6-6 illustrates a variation on a voltage follower design where a sense resistor is used to convert the DAC’s voltage output into a digitally-selectable current source. Adding the resistor network from Example 6-2 would be advantageous in this application. The smaller Rsense is, the less power dissipated across it. However, this also reduces the resolution that the current can be controlled with. The voltage divider, or “window”, DAC configuration would allow the range to be reduced, thus increasing resolution around the range of interest. When working with very small sensor voltages, plan on eliminating the amplifier's offset error by storing the DAC's setting under known sensor conditions. VREF MCP492X VCC+ LOAD IL VCC– Ib SPI™ 3 D V OUT = V REF G ------12 2 Using Multiplier Mode The MCP492X is ideally suited for use as a multiplier/ divider in a signal chain. Common applications include: precision programmable gain/attenuator amplifiers and loop controls (motor feedback). The wide input range (0V – VDD) is an Unbuffered mode and near R-R range in Buffered mode: the > 400 kHz bandwidth, selectible 1x/2x gain and its low power consumption give maximum flexibility to meet the application's needs. To configure the MCP492X in Multiplier mode, connect the input signal to VREF and serially configure the DAC’s input buffer, gain and output value. The DAC’s output can utilize any of Examples 6-1 to 6-6, depending on the application requirements. Example 6-7 is an illustration of how the DAC can operate in a motor control feedback loop. If the Gain Select bit is configured for 1x mode (GA = 1), the resulting input signal will be attenuated by D/4096. If the Gain Select bit is configured for 2x mode (GA = 0), codes < 2048 attenuate the signal, while codes > 2048 gain the signal. VOUT = VIN (D/2048). VDD VOUT 6.9 Rsense A 12-bit DAC provides significantly more gain/attenuation resolution when compared to typical Programmable Gain Amplifiers. Adding an op amp to buffer the output, as illustrated in Examples 6-2 to 6-6, extends the output range and power to meet the precise needs of the application. VRPM_SET IL I b = ---β VRPM V OUT β I L = --------------- × -----------Rsense β + 1 G = Gain select (1x or 2x) D = Digital value of DAC (0 – 4096) VREF MCP492X SPI™ EXAMPLE 6-6: Digitally-Controlled Current Source. 3 VOUT VCC+ + – VCC– Rsense EXAMPLE 6-7: DS21897B-page 26 ZFB VDD Multiplier Mode. © 2007 Microchip Technology Inc. MCP4921/4922 7.0 DEVELOPMENT SUPPORT 7.1 Evaluation & Demonstration Boards The Mixed Signal PICtailTM Board supports the MCP492X family of devices. Please refer to www.microchip.com for further information on this products capabilities and availability. © 2007 Microchip Technology Inc. 7.2 Application Notes and Tech Briefs Application notes illustrating the performace and implementation of the MCP492X are planned but currently not released. Please refer to www.microchip.com for further information. DS21897B-page 27 MCP4921/4922 8.0 PACKAGING INFORMATION 8.1 Package Marking Information Example: 8-Lead MSOP XXXXXX 4921E e3 YWWNNN 712256 8-Lead PDIP (300 mil) XXXXXXXX XXXXXNNN YYWW MCP4921 E/P e3 256 0712 8-Lead SOIC (150 mil) XXXXXXXX XXXXYYWW NNN Legend: XX...X Y YY WW NNN e3 * Note: DS21897B-page 28 Example: Example: MCP4921 E/SN e3 0712 256 Customer-specific information Year code (last digit of calendar year) Year code (last 2 digits of calendar year) Week code (week of January 1 is week ‘01’) Alphanumeric traceability code Pb-free JEDEC designator for Matte Tin (Sn) This package is Pb-free. The Pb-free JEDEC designator ( e3 ) can be found on the outer packaging for this package. In the event the full Microchip part number cannot be marked on one line, it will be carried over to the next line, thus limiting the number of available characters for customer-specific information. © 2007 Microchip Technology Inc. MCP4921/4922 Package Marking Information (Continued) 14-Lead PDIP (300 mil) XXXXXXXXXXXXXX XXXXXXXXXXXXXX YYWWNNN 14-Lead SOIC (150 mil) Example: MCP4922E/P e3 0712256 Example: MCP4922E/SL e3 XXXXXXXXXX XXXXXXXXXX YYWWNNN 14-Lead TSSOP XXXXXX YYWW NNN © 2007 Microchip Technology Inc. 0712256 Example: 4922E/ST e3 0712 256 DS21897B-page 29 MCP4921/4922 8-Lead Plastic Micro Small Outline Package (MS) [MSOP] Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.com/packaging D N E E1 NOTE 1 1 2 e b A2 A c φ L L1 A1 Units Dimension Limits Number of Pins MILLIMETERS MIN N NOM MAX 8 Pitch e Overall Height A – 0.65 BSC – Molded Package Thickness A2 0.75 0.85 0.95 Standoff A1 0.00 – 0.15 Overall Width E Molded Package Width E1 3.00 BSC Overall Length D 3.00 BSC Foot Length L Footprint L1 1.10 4.90 BSC 0.40 0.60 0.80 0.95 REF Foot Angle φ 0° – 8° Lead Thickness c 0.08 – 0.23 Lead Width b 0.22 – 0.40 Notes: 1. Pin 1 visual index feature may vary, but must be located within the hatched area. 2. Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.15 mm per side. 3. Dimensioning and tolerancing per ASME Y14.5M. BSC: Basic Dimension. Theoretically exact value shown without tolerances. REF: Reference Dimension, usually without tolerance, for information purposes only. Microchip Technology Drawing C04-111B DS21897B-page 30 © 2007 Microchip Technology Inc. MCP4921/4922 8-Lead Plastic Dual In-Line (P) – 300 mil Body [PDIP] Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.com/packaging N NOTE 1 E1 1 3 2 D E A2 A L A1 c e eB b1 b Units Dimension Limits Number of Pins INCHES MIN N NOM MAX 8 Pitch e Top to Seating Plane A – – .210 Molded Package Thickness A2 .115 .130 .195 Base to Seating Plane A1 .015 – – Shoulder to Shoulder Width E .290 .310 .325 Molded Package Width E1 .240 .250 .280 Overall Length D .348 .365 .400 Tip to Seating Plane L .115 .130 .150 Lead Thickness c .008 .010 .015 b1 .040 .060 .070 b .014 .018 .022 eB – – Upper Lead Width Lower Lead Width Overall Row Spacing § .100 BSC .430 Notes: 1. Pin 1 visual index feature may vary, but must be located with the hatched area. 2. § Significant Characteristic. 3. Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed .010" per side. 4. Dimensioning and tolerancing per ASME Y14.5M. BSC: Basic Dimension. Theoretically exact value shown without tolerances. Microchip Technology Drawing C04-018B © 2007 Microchip Technology Inc. DS21897B-page 31 MCP4921/4922 8-Lead Plastic Small Outline (SN) – Narrow, 3.90 mm Body [SOIC] Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.com/packaging D e N E E1 NOTE 1 1 2 3 α h b h A2 A c φ L A1 L1 Units Dimension Limits Number of Pins β MILLMETERS MIN N NOM MAX 8 Pitch e Overall Height A – 1.27 BSC – Molded Package Thickness A2 1.25 – – Standoff § A1 0.10 – 0.25 Overall Width E Molded Package Width E1 3.90 BSC Overall Length D 4.90 BSC 1.75 6.00 BSC Chamfer (optional) h 0.25 – 0.50 Foot Length L 0.40 – 1.27 Footprint L1 1.04 REF Foot Angle φ 0° – 8° Lead Thickness c 0.17 – 0.25 Lead Width b 0.31 – 0.51 Mold Draft Angle Top α 5° – 15° Mold Draft Angle Bottom β 5° – 15° Notes: 1. Pin 1 visual index feature may vary, but must be located within the hatched area. 2. § Significant Characteristic. 3. Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.15 mm per side. 4. Dimensioning and tolerancing per ASME Y14.5M. BSC: Basic Dimension. Theoretically exact value shown without tolerances. REF: Reference Dimension, usually without tolerance, for information purposes only. Microchip Technology Drawing C04-057B DS21897B-page 32 © 2007 Microchip Technology Inc. MCP4921/4922 14-Lead Plastic Dual In-Line (P) – 300 mil Body [PDIP] Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.com/packaging N NOTE 1 E1 1 3 2 D E A2 A L A1 c b1 b e eB Units Dimension Limits Number of Pins INCHES MIN N NOM MAX 14 Pitch e Top to Seating Plane A – – .210 Molded Package Thickness A2 .115 .130 .195 Base to Seating Plane A1 .015 – – Shoulder to Shoulder Width E .290 .310 .325 Molded Package Width E1 .240 .250 .280 Overall Length D .735 .750 .775 Tip to Seating Plane L .115 .130 .150 Lead Thickness c .008 .010 .015 b1 .045 .060 .070 b .014 .018 .022 eB – – Upper Lead Width Lower Lead Width Overall Row Spacing § .100 BSC .430 Notes: 1. Pin 1 visual index feature may vary, but must be located with the hatched area. 2. § Significant Characteristic. 3. Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed .010" per side. 4. Dimensioning and tolerancing per ASME Y14.5M. BSC: Basic Dimension. Theoretically exact value shown without tolerances. Microchip Technology Drawing C04-005B © 2007 Microchip Technology Inc. DS21897B-page 33 MCP4921/4922 14-Lead Plastic Small Outline (SL) – Narrow, 3.90 mm Body [SOIC] Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.com/packaging D N E E1 NOTE 1 1 2 3 e h b A A2 c φ L A1 β L1 Units Dimension Limits Number of Pins α h MILLMETERS MIN N NOM MAX 14 Pitch e Overall Height A – 1.27 BSC – Molded Package Thickness A2 1.25 – – Standoff § A1 0.10 – 0.25 Overall Width E Molded Package Width E1 3.90 BSC Overall Length D 8.65 BSC 1.75 6.00 BSC Chamfer (optional) h 0.25 – 0.50 Foot Length L 0.40 – 1.27 Footprint L1 1.04 REF Foot Angle φ 0° – 8° Lead Thickness c 0.17 – 0.25 Lead Width b 0.31 – 0.51 Mold Draft Angle Top α 5° – 15° Mold Draft Angle Bottom β 5° – 15° Notes: 1. Pin 1 visual index feature may vary, but must be located within the hatched area. 2. § Significant Characteristic. 3. Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.15 mm per side. 4. Dimensioning and tolerancing per ASME Y14.5M. BSC: Basic Dimension. Theoretically exact value shown without tolerances. REF: Reference Dimension, usually without tolerance, for information purposes only. Microchip Technology Drawing C04-065B DS21897B-page 34 © 2007 Microchip Technology Inc. MCP4921/4922 14-Lead Plastic Thin Shrink Small Outline (ST) – 4.4 mm Body [TSSOP] Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.com/packaging D N E E1 NOTE 1 1 2 e b A2 A c A1 φ Units Dimension Limits Number of Pins L L1 MILLIMETERS MIN N NOM MAX 14 Pitch e Overall Height A – 0.65 BSC – Molded Package Thickness A2 0.80 1.00 1.05 Standoff A1 0.05 – 0.15 1.20 Overall Width E Molded Package Width E1 4.30 6.40 BSC 4.40 Molded Package Length D 4.90 5.00 5.10 Foot Length L 0.45 0.60 0.75 Footprint L1 4.50 1.00 REF Foot Angle φ 0° – 8° Lead Thickness c 0.09 – 0.20 Lead Width b 0.19 – 0.30 Notes: 1. Pin 1 visual index feature may vary, but must be located within the hatched area. 2. Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.15 mm per side. 3. Dimensioning and tolerancing per ASME Y14.5M. BSC: Basic Dimension. Theoretically exact value shown without tolerances. REF: Reference Dimension, usually without tolerance, for information purposes only. Microchip Technology Drawing C04-087B © 2007 Microchip Technology Inc. DS21897B-page 35 MCP4921/4922 NOTES: DS21897B-page 36 © 2007 Microchip Technology Inc. MCP4921/4922 APPENDIX A: REVISION HISTORY Revision B (February 2007) This revision includes updates to the packaging diagrams. © 2007 Microchip Technology Inc. DS21897B-page 37 MCP4921/4922 NOTES: DS21897B-page 38 © 2007 Microchip Technology Inc. MCP4921/4922 PRODUCT IDENTIFICATION SYSTEM To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office. PART NO. X /XX Device Temperature Range Package Examples: a) b) Device: MCP4921: MCP4921T: MCP4922: MCP4922T: 12-Bit DAC with SPI Interface 12-Bit DAC with SPI Interface (Tape and Reel) (SOIC, MSOP) 12-Bit DAC with SPI Interface 12-Bit DAC with SPI Interface (Tape and Reel) (SOIC, MSOP) Temperature Range: E = -40°C to +125°C Package: MS P SN SL ST = = = = = Plastic MSOP, 8-lead Plastic DIP (300 mil Body), 8-lead, 14-lead Plastic SOIC, (150 mil Body), 8-lead Plastic SOIC (150 mil Body), 14-lead Plastic TSSOP (4.4mm Body), 14-lead © 2007 Microchip Technology Inc. c) d) e) MCP4921T-E/SN: Tape and Reel Extended Temperature, 8LD SOIC package. MCP4921T-E/MS: Tape and Reel Extended Temperature, 8LD MSOP package. MCP4921-E/SN: Extended Temperature, 8LD SOIC package. MCP4921-E/MS: Extended Temperature, 8LD MSOP package. MCP4921-E/P: Extended Temperature, 8LD PDIP package. a) MCP4922T-E/SL: b) MCP4922T-E/ST: c) MCP4922-E/P: d) MCP4922-E/SL: e) MCP4922-E/ST: Tape and Reel Extended Temperature, 14LD SOIC package. Tape and Reel Extended Temperature, 14LD TSSOP package. Extended Temperature, 14LD PDIP package. Extended Temperature, 14LD SOIC package. Extended Temperature, 14LD TSSOP package. DS21897B-page 39 MCP4921/4922 NOTES: DS21897B-page 40 © 2007 Microchip Technology Inc. Note the following details of the code protection feature on Microchip devices: • Microchip products meet the specification contained in their particular Microchip Data Sheet. • Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. • There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data Sheets. Most likely, the person doing so is engaged in theft of intellectual property. • Microchip is willing to work with the customer who is concerned about the integrity of their code. • Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as “unbreakable.” Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act. Information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE. Microchip disclaims all liability arising from this information and its use. Use of Microchip devices in life support and/or safety applications is entirely at the buyer’s risk, and the buyer agrees to defend, indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting from such use. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights. Trademarks The Microchip name and logo, the Microchip logo, Accuron, dsPIC, KEELOQ, microID, MPLAB, PIC, PICmicro, PICSTART, PRO MATE, PowerSmart, rfPIC, and SmartShunt are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. AmpLab, FilterLab, Migratable Memory, MXDEV, MXLAB, SEEVAL, SmartSensor and The Embedded Control Solutions Company are registered trademarks of Microchip Technology Incorporated in the U.S.A. Analog-for-the-Digital Age, Application Maestro, CodeGuard, dsPICDEM, dsPICDEM.net, dsPICworks, ECAN, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB, In-Circuit Serial Programming, ICSP, ICEPIC, Linear Active Thermistor, Mindi, MiWi, MPASM, MPLIB, MPLINK, PICkit, PICDEM, PICDEM.net, PICLAB, PICtail, PowerCal, PowerInfo, PowerMate, PowerTool, REAL ICE, rfLAB, rfPICDEM, Select Mode, Smart Serial, SmartTel, Total Endurance, UNI/O, WiperLock and ZENA are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. SQTP is a service mark of Microchip Technology Incorporated in the U.S.A. All other trademarks mentioned herein are property of their respective companies. © 2007, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved. Printed on recycled paper. Microchip received ISO/TS-16949:2002 certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona, Gresham, Oregon and Mountain View, California. The Company’s quality system processes and procedures are for its PIC® MCUs and dsPIC DSCs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, nonvolatile memory and analog products. In addition, Microchip’s quality system for the design and manufacture of development systems is ISO 9001:2000 certified. © 2007 Microchip Technology Inc. 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