ES51991 11,000 Counts ADC Features • Max. 11,000 counts resolution • Conversion rate selectable by MPU command: 1.6/s Æ 128/s • Input signal full scale: 110mV • 50/60Hz line noise rejection selectable by MPU command • Low battery detection • 3-wire serial bus and EOC signal for MPU I/O port Description ES51991 is an 11000-count dual-slope analogto-digital converter (ADC). The conversion rate and buzzer frequency can be selected or decided by an external microprocessor. The conversion rate can be varied from 1.6 time/sec to 128 times/sec under 4MHz/12MHz crystal oscillation clock. Besides, ES51991 also provides low battery detection, power-down mode, 50/60Hz line noise rejection selection, and I/O port level selection for flexible design. • -3V power operation with internal charge pumping circuit • MPU I/O power level selectable by external control pin • Zero calibration for eliminating offset error • On-chip buzzer driving and frequency selectable by MPU command • Support sleep mode by external CS(chipselect) pin Application Clamp meter Thermometer Portable instrumentation 1 06/09/20 ES51991 11,000 Counts ADC Pin Assignment SSOP-28L 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ES51991 VAGND V12 CAZ CINT CREF+ CREFREF+ REFBUF RAZ VIN+ VINNC 2 28 27 26 25 24 23 22 21 20 19 18 17 16 15 V+ DGND LBAT IO_control CS C+ COSC1 OSC2 uP_VCC BUZOUT EOC SCLK SDATA 06/09/20 ES51991 11,000 Counts ADC Pin Description Pin No Symbol Type 1 2 3 4 5 6 7 8 9 10 11 VAGND V12 CAZ CINT CREF+ CREFREF+ REFBUF RAZ P G O I O I/O I/O I I O O 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 VIN+ VINNC SDATA SCLK EOC BUZout uP_VCC OSC2 OSC1 CC+ CS I/O_control LBAT 27 28 DGND V+ Description Negative supply voltage. Connecting to 3V battery negative terminal. Analog ground Output of band-gap voltage reference. Typically –1.23V Auto-zero capacitor connection. Integrator output. Connect to integral capacitor Positive connection for reference capacitor. Negative connection for reference capacitor. Differential reference high voltage input. Differential reference low voltage input. Buffer output pin. Connect to integral resistor Buffer output pin in high-speed mode. Connect to high-speed integral resistor. I Analog differential high signal input. I Analog differential low signal input. Not connected I/O Serial data I/O pin. Nch open-drain output. I Serial clock input pin. O An indicator for ADC conversion ending. O Buzzer frequency output I MPU I/O port power level selection O Crystal oscillation connection I Crystal oscillation connection O Negative capacitor connection for on-chip DC-DC converter. O Positive capacitor connection for on-chip DC-DC converter. I Chip select input pin. Pull to Low to enter power down mode. I MPU I/O port ground level selection I Low battery configuration. If 3V battery is used, connect it to AGND. The default low-battery threshold voltage is –2.3V. If 9V or other battery voltage is used, the low battery annunciator is displayed when the voltage of this pin is less than V12 G Digital ground O/P Output of on-chip DC-DC converter. 3 06/09/20 ES51991 11,000 Counts ADC Function description 1. Dual Slope A/D－Four Phases Timing ES51991 is a dual-slope analog-to-digital converter (ADC). Figure 1 is a structure of dual-slope integrator. Its measurement cycle has two distinct phases: input signal integration (INT) phase and reference voltage integration (DINT) phase. In INT phase, the input signal is integrated for a fixed time period, then A/D enters DINT phase in which an opposite polarity constant reference voltage is integrated until the integrator output voltage becomes to zero. Since both the time period for input signal integration and the amount of reference voltage are fixed, thus the de-integration time is proportional to the input signal. Hence, we can define the mathematical equation about input signal, reference voltage integration (see Figure 1.): TINT 1 1 V IN (t )dt = × V REF × TDINT ∫ Buf × C int 0 Buf × C int where, V IN (t ) = input signal V REF = reference voltage T INT = integration time (fixed) TDINT = de-integration time (proportional to V IN (t ) ) Cint input signal Buf reference voltage integrator output RAZ BufX10 RAZ integrator output integrator output input signal > 0 integration time different input input signal < 0 different input fixed slope fixed slope Fixed Variable integration deintegration time time Fixed Variable integration deintegration time time integration time Figure 1. the structure of dual-slope integrator and its output waveform. If V IN (t ) is a constant, we can rewrite above equation: TDINT = T INT × V IN V REF 4 06/09/20 ES51991 11,000 Counts ADC Besides the INT phase and DINT phase, ES51991 exploits auto zero (AZ) phase and zero integration (ZI) phase to achieve accurate measurement. In AZ phase, the system offset is stored. The offset error will be eliminated in DINT phase. Thus a higher accuracy could be obtained. In ZI phase, the internal status will be recovered quickly to that of zero input. Thus the succeeding measurements won’t be disturbed by current measurement especially in case of overload. As mentioned above, the measurement cycle of ES51991 contains four phases: (1) auto zero phase (AZ) (2) input signal integration phase (INT) (3) reference voltage integration phase (DINT) (4) zero integration phase (ZI) The time ratios of these four phases, AZ, INT, DINT and ZI to the entire measurement cycle are 8.8%, 32%, 35.2% and 24% respectively. However the actual duration of each phase depends on conversion rate. An example is shown in the table below. A user can easily deduce other cases based on the table. Voltage: CR (times/sec) ZI (ms) 8 30 AZ (ms) INT (ms) DINT (ms) 11 40 44 Note: reference voltage = -100 mV. Voltge+PEAK: CR (times/sec) ZI (ms) 8 30 AZ (ms) INT (ms) DINT (ms) 11 40 60 Note: reference voltage = -100 mV. 5 06/09/20 ES51991 11,000 Counts ADC 2. Component Value Selection for ADC For various application requirements on conversion rate and input full range, we suggest nominal values for external components of ADC in Figure 1 to obtain better performance. Under default condition with operating clock = 12 MHz: (1) conversion rate = 8 times/sec (2) reference voltage = -100 mV (3) input signal full scale = 110 mV (sensitivity = 10 uV) We suggest that Cint = 68 nF, Buf = 56 kΩ If a user selects a different conversion rate rather than default, the integration capacitor Cint value must be changed according to the following rule for better performance: Cint × (conversion rate) = (68 nF) × (8 times/sec). A smaller Cint reduces the input full range. However a larger Cint might have weaker noise immunity than the suggested one. A user could enlarge the input full range by changing reference voltage (Vref) and the amount of integration resistor (Buf). For example, if Vref & Buf are enlarged as twice than the default values then the input full range becomes 220 mV. The input full range can be enlarged up to 1.1V (10 times than the default case). We list general rules in below which might be helpful in determining component values. Buf / (reference voltage) = 56 kΩ / (-100 mV) 6 06/09/20 ES51991 11,000 Counts ADC 3. Special function 3.1 Zero and RZero Calibration The Zero and RZero calibration are designed for removing the error rise from the propagation delay of internal component. In Zero or RZero calibration mode, ES51991 outputs a calibration value. The normal measurement value must minus the calibration value to cancel the error and obtain a more accurate value. The following block diagram performs the difference between basic structures of normal mode, Zero calibration and RZero Calibration. We suggest users to do zero-calibration in most applications. V IN + IN + (a ) N o rm a l m o d e D u a l S lo p e ADC IN - V IN - IN + V IN + D u a l S lo p e ADC (b ) Z ero m o d e IN - V IN - IN + V IN + D u a l S lo p e ADC (c ) R Z ero m o d e V IN - IN - 7 06/09/20 ES51991 11,000 Counts ADC 3.2 Buzzer Setup When the bit BUZ of ID Byte is set to “H”, the BUZOUT will output a square signal of MPU I/O swing level to drive a external buzzer. The buzzer frequency is determined by the bits B0/B1/B2 of STATUS Byte3. The configuration of buzzer frequency is listed at the following table. B2/B1/B0 BUZout (kHz) 111 110 101 100 011 010 001 000 4.00 3.33 3.08 2.67 2.22 2.00 1.33 1.00 3.3 Low Battery Detection In a case of 3V battery power, the pin LBAT must be shorted to AGND. And the system will have low battery detection level about 2.3V. In another case of 9V or other battery power, the low battery detection happens when the voltage of LBAT is less than –1.23V below GND. And the bit LBAT of STATUS Byte3 will be set to high. A recommended application is shown as following: Low battery test (9V) 9V BA 680K LBAT TT 230K 0.1u AGND V- 0V The low battery detection level is around 7V 3.4 Sleep Mode When the pin CS is connected to V- or GND (depended on I/O_control level), the ES51991 will enter sleep mode. In Sleep mode, the chip draws a little supply current. It could extend the battery life. To leave sleep mode or stay in normal mode, the pin CS must be connected to AGND or floating. 8 06/09/20 ES51991 11,000 Counts ADC 4. MPU I/O function definition Write command: ID byte, Status byte1, Status byte2, Status byte3 START BIT 1 1 0 0 0 1 B U Z 0 A C K A C K A C K A C K WRITE STOP BIT Read command: ID byte, Status byte1, Status byte2, Status byte3, Data byte1, Data byte2 START BIT 1 1 0 0 0 B U 1 Z 1 A C K A C K A C K A C K READ A C K N A K STOP BIT ID byte: 1 1 0 Status byte1: 0 0 C0 Status byte2: S60 RZERO ZERO Status byte3: 0 0 B0 Data byte1: D0 D1 D2 Data byte2: D8 D9 D10 0 0 1 BUZ R/W C1 C2 SIGN SEL4M X 0 X X X X B1 B2 LBAT X X D3 D4 D5 D6 D7 D11 D12 D13 X X 9 06/09/20 ES51991 11,000 Counts ADC R/W: set to “H” is in read mode, set to “L” is in write mode C2/C1/C0/S60: Conversion rate selection, the default is [0000] S60 C2/C1/C0 L H 101 128/s 128/s 100 96/s 96/s 011 64/s 76.8/s 010 32/s 38.4/s ! 001 16/s 19.2/s* ! 000 8/s 9.6/s* 110 3.2/s!* 3.84/s* !* 111 1.6/s 1.92/s* Crystal: 12MHz !: 50Hz line noise rejection, *: 60Hz line noise rejection SEL4M: “H” is XTAL is 4MHz version, “L” is default 12MHz XTAL S60 C2/C1/C0 X 101 128/s 100 64/s 011 64/s 010 32/s 001 16/s! 000 8/s! 110 3.2/s!* 111 1.6/s!* Crystal :4MHz SIGN: “H” is negative, “L” is positive LBAT: “H” is low battery detection flag active, the default is “L” RZERO: “H” is RZero calibration mode “ON”, the default is “L” ZERO: “H” is Zero calibration mode “ON”, the default is “L” B2/B1/B0: Buzzer frequency selection (independent with conversion rate) BUZ: “H” is buzzer turn on and “L” is turn off, the default is turn off. 10 06/09/20 ES51991 11,000 Counts ADC Buzzer ON START BIT 1 1 0 0 0 1 1 A C K STOP BIT Buzzer OFF START BIT 1 1 0 0 0 1 0 A C K STOP BIT D13-D0: ADC output data. Binary code format. 5. Power and I/O output level selection Power z Charge pump output for positive supply voltage(V+) z External DC source to V+ is available by floating the charge pump capacitor I/O output level selectable z uP_VCC provided by external DC source (the same high level with MPU) z A control pin (I/O_control) selects the low level to –3V(V-) or 0V(DGND) I/O level uP_VCC I/O_control Example H L 3 H +3V 0V Ex.1 3 L +3V -3V Ex.2 0 L 0V -3V Ex.3 11 06/09/20 ES51991 11,000 Counts ADC ES5199X V+ C- uP_VCC +3V C+ I/O_control SCLK SDATA EOC BUZOUT CS +3V 0V GND V- Ex.1 -3V ES5199X C- V+ uP_VCC +3V C+ I/O_control SCLK SDATA EOC BUZOUT CS +3V -3V GND V- Ex.2 -3V ES5199X C- V+ uP_VCC C+ I/O_control SCLK SDATA EOC BUZOUT CS 0V -3V GND V- Ex.3 -3V 12 06/09/20 ES51991 11,000 Counts ADC Absolute Maximum Ratings Characteristic Supply Voltage (V- to AGND) Analog Input Voltage V+ AGND/DGND Digital Input Power Dissipation. Flat Package Operating Temperature Storage Temperature Rating -3.6V V- -0.6 to V+ +0.6 V+ ≥ (AGND/DGND+0.5V) AGND/DGND ≥ (V- -0.5V) V- -0.6 to DGND +0.6 or V+ +0.6 500mW 0℃ to 70℃ -25℃ to 125℃ DC Electrical Characteristics TA=25℃, VCM=0V, V- = -3V Parameter Power supply Operating supply current Conversion rate = 8/sec. Voltage roll-over error Voltage nonlinearity Symbol Test Condition VIDD Normal operation (XTAL=12MHz) ISS In sleep mode REV NLV Input Leakage Low battery flag voltage Internal pull-high to uP_Vcc current Internal pull-low to V- current Zero input reading Reference voltage and open circuit voltage for 110Ω measurement VREF Reference voltage temperature coefficient TCRF Best case straight line V- to AGND CS (uP_Vcc=3V) CS(uP_Vcc=0V) I/O_control (V-=-3V) 10MΩ input resistor zero cal. by MPU 100KΩ resistor between VRH and AGND 100KΩ resister Between VRH 0℃<TA<70℃ Min. -3.3 Typ. -3.0 Max -2.5 Units V — 2.0 2.2 mA — 2.5 5 µA — — ±0.05 %F.S1 — — ±0.05 %F.S 1 -2.3 5 1.5 10 -2.2 pA V -2.4 uA 1.5 uA -000 000 +000 counts -1.33 -1.23 -1.13 V — 50 — ppm/℃ Note: 1.Full Scale 13 06/09/20 ES51991 11,000 Counts ADC AC Electrical Characteristics Parameter Symbol Min. Typ. Max. Unit SCLK clock frequency SCLK clock time “L” SLCK clock time “H” SDATA output delay time SDATA output hold time Start condition setup time Start condition hold time Data input setup time Data input hold time Stop condition setup time SCLK/SDATA rising time SCLK/SDATA falling time Bus release time EOC setup time in read mode EOC hold time in read mode fSCLK tLOW tHIGH tAA tDH tSU.STA tHD.STA tSU.DAT tHD.DAT tSU.STO tR tF tBUF tSU.EOC tHD.EOC 4.7 4.0 0.1 100 4.7 4.0 200 0 4.7 4.7 0 0 - 100 3.5 1.0 0.3 - kHz - - us ns us ns us ns ns I/O timing diagram SCLK SDATA IN SDATA OUT Read mode EOC timing diagram EOC t t S U .E O C H D .E O C SD A TA SCLK S tart co n d itio n S to p co n d itio n 14 06/09/20 ES51991 11,000 Counts ADC Application example 7.5V ZD 5.6V ZD + *1 MPU power VDD 10uF *4 MPU *2 0.1uF V- or DGND VSS + 0.1uF I/O port 10uF 470 nF VAGND V12 CAZ **68nF CINT 91k 220 nF CREFREF+ REFBUF 10k VR RAZ VIN+ **56k VIN- 28 2 27 3 26 4 25 5 24 6 7 8 9 10 ES51991 CREF+ 1 23 22 21 20 19 11 18 12 17 13 16 14 15 V+ DGND LBAT IO_control CS 12M or 4MHz C+ ***R 470nF COSC1 *3 OSC2 uP_VCC BUZOUT EOC 15k SCLK SDATA 5.6V ZD V- 1 uF Input 100k **10nF Note: Zener diodes in above circuit are used for IC protection, so MUST be soldered on PCB first. *1*2*3*4: Depend on power design ** Depends on conversion rates setting: V-=-3.0V (a)Conversion rate 128/s 96/s 76.8/s 64/s 38.4/s 32/s 19.2/s (b)CINT(uF) 0.01 0.01 0.01 0.022 0.022 0.033 0.033 (c)RBUF(kΩ) 22 30 39 22 36 27 47 (a)Conversion rate 16/s 9.6/s 8/s 3.84/s 3.2/s 1.92/s 1.6/s (b)CINT(uF) 0.068 0.047 0.068 0.1 0.1 0.22 0.22 (c)RBUF(kΩ) 27 68 56 82 91 68 91 *** R=10~22MΩ resistor is optional 15 06/09/20 ES51991 11,000 Counts ADC Product Outline: SSOP-28L 16 06/09/20