SBOU024C august   2004  – july 2023 PGA309

 

  1.   1
  2.   Read This First
    1.     About This Manual
    2.     Related Documentation from Texas Instruments
    3.     If You Need Assistance
    4.     Information About Cautions and Warnings
    5.     FCC Warning
    6.     Trademarks
  3. 1Introduction
    1. 1.1  PGA309 Functional Description
    2. 1.2  Sensor Error Adjustment Range
    3. 1.3  Gain Scaling
    4. 1.4  Offset Adjustment
    5. 1.5  Voltage Reference
    6. 1.6  Sensor Excitation and Linearization
    7. 1.7  ADC for Temperature Sensing
    8. 1.8  External EEPROM and Temperature Coefficients
    9. 1.9  Fault Monitor
    10. 1.10 Over-Scale and Under-Scale Limits
    11. 1.11 Power-Up and Normal Operation
    12. 1.12 Digital Interface
    13. 1.13 Pin Configuration
  4. 2Detailed Description
    1. 2.1  Gain Scaling
      1. 2.1.1 PGA309 Transfer Function
      2. 2.1.2 Solving For Gain Settings
    2. 2.2  Offset Scaling
    3. 2.3  Zero DAC and Gain DAC Architecture
    4. 2.4  Output Amplifier
    5. 2.5  Reference Voltage
    6. 2.6  Linearization Function
      1. 2.6.1 System Definitions
      2. 2.6.2 Key Linearization Design Equations
        1. 2.6.2.1 Lin DAC Counts Conversion
      3. 2.6.3 Key Ideal Design Equations
        1. 2.6.3.1 Linearization Design
        2.       37
    7. 2.7  Temperature Measurement
      1. 2.7.1 Temp ADC Start-Convert Control
      2. 2.7.2 External Temperature Sensing with an Excitation Series Resistor
    8. 2.8  Fault Monitor
    9. 2.9  Over-Scale and Under-Scale
      1. 2.9.1 Over-Scale and Under-Scale Calculation
      2.      44
    10. 2.10 Noise and Coarse Offset Adjust
    11. 2.11 General AC Considerations
  5. 3Operating Modes
    1. 3.1 Power-On Sequence and Normal Stand-Alone Operation
    2. 3.2 EEPROM Content and Temperature Lookup Table Calculation
      1. 3.2.1 Temperature Lookup Table Calculation
        1. 3.2.1.1 Temperature Lookup Table Calculation
        2.       52
        3.       53
    3. 3.3 Checksum Error Event
    4. 3.4 Test Pin
    5. 3.5 Power-On Initial Register States
      1. 3.5.1 PGA309 Power-Up State
  6. 4Digital Interface
    1. 4.1  Description
    2. 4.2  Two-Wire Interface
      1. 4.2.1 Device Addressing
      2. 4.2.2 Two-Wire Access to PGA309
    3. 4.3  One-Wire Interface
    4. 4.4  One-Wire Interface Timeout
    5. 4.5  One-Wire Interface Timing Considerations
    6. 4.6  Two-Wire Access to External EEPROM
    7. 4.7  One-Wire Interface Initiated Two-Wire EEPROM Transactions
    8. 4.8  PGA309 Stand-Alone Mode and Two-Wire Transactions
    9. 4.9  PGA309 Two-Wire Bus Master Operation and Bus Sharing Considerations
    10. 4.10 One-Wire Operation with PRG Connected to VOUT
    11. 4.11 Four-Wire Modules and One-Wire Interface (PRG)
  7. 5Application Background
    1. 5.1 Bridge Sensors
    2. 5.2 System Scaling Options for Bridge Sensors
      1. 5.2.1 Absolute Scale
      2. 5.2.2 Ratiometric Scale
    3. 5.3 Trimming Real World Bridge Sensors for Linearity
    4. 5.4 PGA309 Calibration Procedure
  8. 6Register Descriptions
    1. 6.1 Internal Register Overview
    2. 6.2 Internal Register Map
      1. 6.2.1 Register 0: Temp ADC Output Register (Read Only, Address Pointer = 00000)
      2. 6.2.2 Register 1: Fine Offset Adjust (Zero DAC) Register (Read/Write, Address Pointer = 00001)
      3. 6.2.3 Register 2: Fine Gain Adjust (Gain DAC) Register (Read/Write, Address Pointer = 00010)
      4. 6.2.4 Register 3: Reference Control and Linearization Register (Read/Write, Address Pointer = 00011)
      5. 6.2.5 Register 4: PGA Coarse Offset Adjust and Gain Select/Output Amplifier Gain Select Register (Read/Write, Address Pointer = 00100)
      6. 6.2.6 Register 5: PGA Configuration and Over/Under-Scale Limit Register (Read/Write, Address Pointer = 00101)
      7. 6.2.7 Register 6: Temp ADC Control Register (Read/Write, Address Pointer = 00110)
      8. 6.2.8 Register 7: Output Enable Counter Control Register (Read/Write, Address Pointer = 00111)
      9. 6.2.9 Register 8: Alarm Status Register (Read Only, Address Pointer = 01000)
  9.   A External EEPROM Example
    1.     A.1 PGA309 External EEPROM Example
      1.      A.1.1 Gain and Offset Scaling for External EEPROM
      2.      94
  10.   B Detailed Block Diagram
    1.     B.1 Detailed Block Diagram
  11.   C Glossary
  12.   Revision History

2.7 Temperature Measurement

The center of the PGA309 temperature measurement circuitry is the Temp ADC. The Temp ADC and its associated PGA, input mux, and REF mux provide a flexible and configurable temperature sensing block for reading either on-chip or external temperatures. Figure 2-15 illustrates the PGA309 temperature sense block.

The internal temperature sensing is accomplished by using on-chip diode junctions. The Internal Temperature Mode is configured through setting the bits in Register 6 to the values shown in Table 2-7 and Table 2-8. The Temp ADC output is presented in Register 0 in 12-bit + sign extended, right-justified, two’s complement data format (see Table 2-9). The resolution, for the Temp ADC in Internal Temperature Mode, is 0.0625°C/count and the accuracy is ±2°C. The temperature accuracy is a relative error that is calibrated out with the PGA309 + sensor calibration to the accuracy of the calibration temperature measurement equipment.

GUID-7712E183-D238-4F97-B1BF-03A0192E139D-low.gifFigure 2-15 Temperature Sense Block
Table 2-7 Internal Temperature Mode Configuration—Register 6
BitBit NameBit StateConfiguration
15RFB0Reserved Factory Bit—set to 0 for proper operation
14RFB0Reserved Factory Bit—set to 0 for proper operation
13ADC2X0Unused for Internal Temperature Mode; set to zero.
12ADCS0
11ISEN0
10CEN1Enable the Temp ADC
9TEN1Internal Temperature Mode selected
8AREN0Unused for Internal Temperature Mode; set to zero.
7RV10
6RV00
5M10
4M00
3G10
2G00
1R11See Table 2-8.
0R01See Table 2-8.
Table 2-8 Internal Temperature Mode Resolution—Register 6
R1R0Temp ADC Resolution (Conversion Time) Select
TEN = ‘1’
009-Bit + Sign, Right-Justified, Sign-Extended, Twos Complement, 0.5°C (3ms)
0110-Bit + Sign, Right-Justified, Twos Complement, Sign-Extended, 0.25°C (6ms)
1011-Bit + Sign, Right-Justified, Twos Complement, Sign-Extended, 0.125°C (12ms)
1112-Bit + Sign, Right-Justified, Twos Complement, Sign-Extended, 0.0625°C (24ms)
Table 2-9 Internal Temperature Mode Data —Register 0(1)
Temperature
(°C)		Digital Output (Binary)
AD15…………AD0		Digital Output
(Hex)
1280000 1000 0000 00000800
127.93750000 0111 1111 111107FF
1000000 0110 0100 00000640
800000 0101 0000 00000500
750000 0100 1011 000004B0
500000 0011 0010 00000320
250000 0001 1001 00000190
0.250000 0000 0000 01000004
0.00000 0000 0000 00000000
−0.251111 1111 1111 1100FFFC
−251111 1110 0111 0000FE70
−551111 1100 1001 0000FC90
−1281111 1000 0000 0000F800
(1) The resolution for the Temp ADC in Internal Temperature Mode is 0.0625°C/count.

For Positive Temperatures (for example, +50°C):
Twos Complement is not performed on positive numbers. Therefore, simply convert the number to binary code with the 16-bit, right-justified format, and MSB = 0 to denote a positive sign. Extend this sign into the upper 4 bits.
Example: (50°C)/(0.0625°C/count) = 800 = 320h = 0011 0010 0000 Twos Complement 16-bit, right-justified, sign-extended format = 0000 0011 0010 0000 = 0320h.

For Negative Temperatures (for example, −25°C):
Generate the Twos Complement of a negative number by complementing the absolute value binary number and adding 1. Extend the sign, denoting a negative number with MSB = 1. Extend the sign to the upper 4 bits to form the 16-bit word.
Example: (| −25°C|)/(0.0625°C/count) = 400 = 190h = 0001 1001 0000 Twos Complement format: 1110 0111 0000 Extend the sign and create the 16-bit word: 1111 1110 0111 0000 = FE70h

There are several configurations possible for the Temp ADC when External Temperature Mode is selected. In this mode, the TEMPIN pin is read to determine temperature. TEMPIN may be referenced to GND, VEXC, or VREF. VOUT may also be selected to be read relative to GND through the Temp ADC. Figure 2-16 shows the allowable Temp ADC input mux configurations.

Note:

In Configuration #3, the VOUT pin is read, not the VFB pin. Therefore, this value may be different from VOUT FILT. Refer to Figure 1-1 and Figure 2-5.

GUID-FB34CAD5-EDD7-46CC-AA93-381556A6DBD7-low.gifFigure 2-16 Temp ADC Input Mux Options
Table 2-10 Temp ADC PGA Gain Select—Register 6
G1
[3]		G0
[2]		Temp ADC
PGA Gain
001
012
104
118

The temperature sense block also contains a 7µA (typ) current source, ITEMP, that is enabled by a logic ‘1’ written to Register 6, bit 11, ISEN. A logic ‘0’ disables ITEMP from the TEMPIN pin. This current source can be used to excite an external resistive temperature device or diode for bridge sensor temperature measurement, as shown in Figure 2-17.

GUID-C0D66E8A-59F3-4208-B1C3-FF16E64F0090-low.gifFigure 2-17 ITEMP for External Temperature Measurement

The Temp ADC has several choices for its reference voltage for analog-to-digital conversions when used in External Temperature mode; these are illustrated in Table 2-11 and Figure 2-15. The resolution of the Temp ADC when used in External Temperature mode is also register-selectable (see Table 2-12).

Table 2-11 Temp ADC Reference Select—Register 6
AREN
[8]		RV1
[7]		RV0
[6]		Temp ADC Reference
(VREFT)
000VREF
001VEXC
010VSA
011Factory Reserved
1X(1)X(1)Temp ADC Internal REF (2.048V)
(1) ‘X’ = don’t care.
Table 2-12 Temp ADC(1) Resolution (Conversion time)—Register 6
R1
[1]		R0
[0]		External Signal Mode [TEN=0],
External Reference [AREN=0]		External Signal Mode [TEN=0],
Internal Reference [2.048V, AREN=1]
0011-Bit + Sign, Right-Justified, Sign-Extended (6ms)11-Bit + Sign, Right-Justified, Sign-Extended (8ms)
0113-Bit + Sign, Right-Justified, Sign-Extended (24ms)13-Bit + Sign, Right-Justified, Sign-Extended (32ms)
1014-Bit + Sign, Right-Justified, Sign-Extended (50ms)14-Bit + Sign, Right-Justified, Sign-Extended (64ms)
1115-Bit + Sign, Right-Justified, Sign-Extended (100ms)15-Bit + Sign, Right-Justified, Sign-Extended (128ms)
(1) Temp ADC uses Twos Complement data format.