TI PGA400QYZSRQ1

PGA400-Q1
www.ti.com
SLDS186 – MARCH 2012
PRESSURE SENSOR SIGNAL CONDITIONER
Check for Samples: PGA400-Q1
1 DEVICE OVERVIEW
1.1
FEATURES
1
• Analog Features
– Analog Front-End for
Resistive Bridge Sensors
– Self-Oscillating Demodulator for
Capacitive Sensors
– On-Chip Temperature Sensor
– Programmable Gain
– 16-Bit, 1MHz Sigma-Delta Analog-to-Digital
Converter for Signal Channel
– 10-Bit Sigma-Delta Analog-to-Digital
Converter for Temperature Channel
– Two 12–Bit DAC Outputs
• Digital Features
– Microcontroller Core
• 10 MHz 8051 WARP Core
– 2 Clocks Per Instruction Cycle
• On–Chip Oscillator
– Memory
• 8 KB of OTP Memory
1.2
•
•
•
• 89 Bytes of EEPROM
• 256 Bytes Data SRAM
• Peripheral Features
– Serial Peripheral Interface (SPI™)
– Inter-Integrated Circuit (I2C™)
– One-Wire Interface
– Two Input Capture Ports
– Two Output Compare Ports
– Software Watchdog Timer
– Oscillator Watchdog
– Power Management Control
– Analog Low-Voltage Detect
• General Features
– Automotive Temperature Range: –40°C to
125°C
– Power Supply: 4.5 V to 5.5 V Operational,
–5.5 V to 16 V Abs Max
– Qualified in accordance with AEC-Q100
– WCSP-36 package
APPLICATIONS
Pressure Sensor Signal Conditioning
Level Sensor Signal Conditioning
Humidity Sensor Signal Conditioning
1.3
DEVICE OVERVIEW
The PGA400-Q1 is an interface device for piezoresistive, strain gauge and capacitive sense elements.
The device incorporates the analog front end that directly connects to the sense element and has voltage
regulators and oscillator. The device also includes sigma-delta analog-to-digital converter, 8051 WARP
core microprocessor and OTP memory. Sensor compensation algorithms can be implemented in software.
The PGA400-Q1 also includes 2 DAC outputs.
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date. Products conform to
specifications per the terms of the Texas Instruments standard warranty. Production
processing does not necessarily include testing of all parameters.
Copyright © 2012, Texas Instruments Incorporated
PGA400-Q1
SLDS186 – MARCH 2012
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2 FUNCTIONAL BLOCK DIAGRAM
2
FUNCTIONAL BLOCK DIAGRAM
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3 DEVICE INFORMATION
DIE-SIZE BALL GRID ARRAY (WCSP)
36 PINS
(TOP VIEW)
6
5
4
3
2
1
A
B
C
D
E
F
PIN DESCRIPTIONS
NAME
NO.
AVDD
C6
Linear regulator output for internal analog circuit supply
DESCRIPTION
CS
F5
Serial peripheral interface chip select
DVDD
F6
Linear regulator output for internal digital circuit supply
GND
B2, B3, B5, B6, C3, C4, C5,
D5, E5, E6
Ground
GPIO_1 / IC_1 / SDA
C2
General purpose IO 1 / input capture port 1 / I2C Data
GPIO_2 / IC_2
D2
General purpose IO 2 / input capture port 2
GPIO_3 / OC_1/SCL
E3
General purpose IO 3 / output compare port 1 / I2C Clock
GPIO_4 / OC_2
D3
General purpose IO 4 / output compare port 2
GPIO_5
F1
General purpose IO 5
ICAP1
A2
Capactive sensor drive current 1
ICAP2
A5
Capactive sensor drive current 2
SDO
F4
Serial peripheral interface slave data out
SDI
F3
Serial peripheral interface slave data in
RXD
D4
8051 UART Rx (Port 3_0)
SCK
F2
Serial Peripheral Interface clock
TXD
E4
8051 UART Tx (Port 3_1)
VBRG
B1
Resistive bridge supply voltage
VDD
D6
Input power supply
VIN1N / CR1
A3
Resistive sensor 1 negative input / capacitive sensor 1 reference input
VIN1P / CP1
A1
Resistive sensor 1 positive input / capacitive sensor 1 positive input
VIN2N / CR2
A6
Resistive sensor 2 negative input / capacitive sensor 2 reference input
VIN2P / CP2
A4
Resistive sensor 2 positive input / capacitive sensor 2 positive input
VIN3
B4
External temperature sensor input
VOUT1/OWI
D1
DAC1 output / One-wire interface
VOUT2
C1
DAC2 output
VP_OTP
E1
One-time programmable memory programming voltage
XTAL
E2
External crystal input
DEVICE INFORMATION
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4 ABSOLUTE MAXIMUM RATINGS
ABSOLUTE MAXIMUM RATINGS (1)
4.1
PARAMETER
MIN
MAX
Power Supply Voltage
–5.5
16
V
Voltage at VP_OTP
–0.3
8.0
V
Voltage at sensor input and drive pins
–0.3
3.6
V
Voltage at any IO pin except at VOUT1/OWI
–0.3
VDD + 0.3
V
Voltage at VOUT1/OWI pin
–0.3
7.5
V
IDD, Short
on VOUT1
or VOUT2
Supply Current
–45
45
mA
Iout1, Iout2
Output Current
–30
30
mA
VDD,
Continuous
Human Body Model (HBM) - AEC-Q100-002D
ESD
Tjmax
Maximum Junction Temperature
Tstg
Storage Temperature
Tlead
(1)
4.2
±2
Field Induced Charge Device Model (CDM) - AEC-Q100-11B
KV
±500
–40
Lead Temperature (Soldering, 10sec)
UNIT
V
150
°C
150
°C
260
°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings
only and functional operation of the device at these or any other conditions beyond those indicated under “Recommended Operating
Conditions” are not implied. Exposure to Absolute-Maximum-Rated conditions for extended periods may affect device reliability.
RECOMMENDED OPERATING CONDITIONS
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
VDD
Power supply voltage
IDD
Power supply current - normal mode
Power supply current - low power mode
MIN
TYP
MAX
UNIT
4.5
5
5.5
V
VDD = 5V, No load on VBRG, No load
on DAC1 and DAC2
13.6
mA
VDD = 5.5V, No load on VBRG, No
load on DAC1 and DAC2, AFE turned
OFF
9.5
mA
VP_OTP
OTP programming voltage
I_VP_OTP
OTP programming current
tprog_OTP
OTP programming timing per byte
120
TA
Operating ambient temperature
4
7.0
7.8
V
3
mA
–40
125
°C
–40
140
°C
250
µs
During OTP Programming
Programming temperature
OTP or EEPROM
Micro start-up time
VDD ramp rate 1V/µs
ABSOLUTE MAXIMUM RATINGS
7.4
µs
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SLDS186 – MARCH 2012
5 ELECTRICAL CHARACTERISTICS
5.1
Overvoltage Protection
PARAMETER
OV
Overvoltage protection threshold
OVhyst
Overvoltage protection hysteresis
5.2
TEST CONDITIONS
5.5
MAX
6.1
7.0
UNIT
V
mV
Regulators
PARAMETER
TEST CONDITIONS
AVDD voltage
CAVDD = 100 nF
I_AVDD
AVDD current
VAVDD = 3.3 V
5.3
TYP
410
VAVDD
VDVDD
MIN
DVDD voltage
MIN
TYP
MAX
UNIT
3.3
V
5
mA
No EEPROM Programming
3.3
V
EEPROM Programming
3.6
V
Internal Oscillator and External Crystal Interface
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
40
41.6
MHz
43.7
MHz
INTERNAL OSCILLATOR
Internal Oscillator frequency
Tamb = 25 °C
38.4
Internal Oscillator frequency
Accross operating temperature
36.3
EXTERNAL 40-MHZ CRYSTAL
Low-level input voltage on XTAL
–0.3
0.1× VDD
V
High-level input voltage on XTAL
0.7 × VDD
VDD + 0.3
V
ELECTRICAL CHARACTERISTICS
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5.4
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Sensor Supply
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VBRG SUPPLY FOR RESISTIVE BRIDGE SENSORS
0.44 kΩ ≤ RBRG ≤ 20 kΩ
VBRG
Supply Voltage
RBRG
Resistive Bridge Resistance
CBRG
Capacitive Load
RBRG = 20 kΩ
Line regulation
VDD = 4.5V, 5.5V, RBRG = 0.44 kΩ
Load regulation
VDD = 5.0 V, 10 µA ≤ ILOAD ≤ 10 mA
3.2
3.33
3.4
V
20
KΩ
500
pF
-40
40
mV
-40
40
mV
CI[2:0] = 000, ICAP_V = 100 mV
-5.3
-4.3
CI[2:0] = 001, ICAP_V = 100 mV
-8
-6.6
CI[2:0] = 010, ICAP_V = 100 mV
-10.8
-8.8
CI[2:0] = 011, ICAP_V = 100 mV
-13.5
-11.1
CI[2:0] = 100, ICAP_V = 100 mV
-16.2
-13.3
CI[2:0] = 101, ICAP_V = 100 mV
-18.9
-15.5
CI[2:0] = 110, ICAP_V = 100 mV
-21.6
-17.8
CI[2:0] = 111, ICAP_V = 100 mV
0.44
ICAPx SUPPLY FOR CAPACITIVE SENSORS
ICAP_A
Supply Current Amplitude on ICAP,
TA = 25°C
-24.4
-20.1
CI[2:0] = 000, ICAP_V = 3.2 V
4.5
5.6
CI[2:0] = 001, ICAP_V = 3.2 V
6.9
8.5
CI[2:0] = 010, ICAP_V = 3.2 V
9.2
11.3
CI[2:0] = 011, ICAP_V = 3.2 V
11.5
14.1
CI[2:0] = 100, ICAP_V = 3.2 V
13.6
16.7
CI[2:0] = 101, ICAP_V = 3.2 V
15.8
19.2
CI[2:0] = 110, ICAP_V = 3.2 V
18.1
22.1
CI[2:0] = 111, ICAP_V = 3.2 V
20.4
24.8
-5.0
+5.0
Variation over temperature
CPx_V,
CRx_V
Capacitive Sensor Drive - Voltage at
CPx and CRx pins
CV[1:0] = 00
70
90
110
CV[1:0] = 01
255
300
345
CV[1:0] = 10
425
500
575
CV[1:0] = 11
595
700
805
CR[1:0] = 00, RREF = 78 kΩ
-1.07
-1.01
-0.94
CR[1:0] = 01, RREF = 78 kΩ
-2.13
-1.97
-1.82
CR[1:0] = 10, RREF = 78 kΩ
-4.24
-3.93
-3.63
CR[1:0] = 11, RREF = 78 kΩ
-8.45
-7.85
-7.26
14
16
18
µA
%
mV
SELF OSCILLATING CURRENT MODE DEMODULATOR FOR CAPACITIVE SENSORS
RF / RREF
Gain in Transimpedance amplifier
Cf
Feedback Capacitor in
Transimpedance amplifier
5.5
PARAMETER
TEST CONDITIONS
MIN
150
2.7
(1)
Total Error
2.8
UNIT
°C
bits
8
(1)
Offset
MAX
10
Temperature ADC Update Rate
Gain
TYP
–40
Temperature ADC Resolution
6
pF
Temperature Sensor
Temperature Range
(1)
V/V
ms
2.9
LSB/°C
-105
-66
LSB
-4
4
°C
The Temperature ADC Value is given by the equation: ADC Code = Gain*Temperature (in °C) + Offset
ELECTRICAL CHARACTERISTICS
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5.6
SLDS186 – MARCH 2012
Analog Front Ends
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
STAGE 1 GAIN FOR RESISTIVE BRIDGE SENSORS
Gain Steps
Bandwidth
5.7
Sx_G1[2:0] = 000
3.0
Sx_G1[2:0] = 001
4.4
Sx_G1[2:0] = 010
6.8
Sx_G1[2:0] = 011
10.2
Sx_G1[2:0] = 100
14.6
Sx_G1[2:0] = 101
25.5
Sx_G1[2:0] = 110
34.0
Sx_G1[2:0] = 111
51.0
–3 dB, Gain = 111
7
V/V
KHz
Stage 2 Gain
PARAMETER
Gain Steps
Bandwidth
TEST CONDITIONS
MIN
TYP
MAX
Sx_G2[4:0] = 00000
0.97
1.01
1.05
Sx_G2[4:0] = 00001
1.06
1.11
1.16
Sx_G2[4:0] = 00010
1.18
1.23
1.28
Sx_G2[4:0] = 00011
1.31
1.37
1.42
Sx_G2[4:0] = 00100
1.45
1.52
1.58
Sx_G2[4:0] = 00101
1.61
1.68
1.76
Sx_G2[4:0] = 00110
1.79
1.87
1.94
Sx_G2[4:0] = 00111
1.98
2.07
2.16
Sx_G2[4:0] = 01000
2.20
2.29
2.39
Sx_G2[4:0] = 01001
2.44
2.55
2.65
Sx_G2[4:0] = 01010
2.71
2.83
2.94
Sx_G2[4:0] = 01011
3.00
3.13
3.26
Sx_G2[4:0] = 01100
3.34
3.48
3.62
Sx_G2[4:0] = 01101
3.74
3.90
4.06
Sx_G2[4:0] = 01110
4.12
4.30
4.48
Sx_G2[4:0] = 01111
4.61
4.81
5.01
Sx_G2[4:0] = 10000
5.09
5.31
5.54
Sx_G2[4:0] = 10001
5.67
5.92
6.16
Sx_G2[4:0] = 10010
6.26
6.52
6.79
Sx_G2[4:0] = 10011
6.93
7.23
7.53
Sx_G2[4:0] = 10100
7.70
8.04
8.37
Sx_G2[4:0] = 10101
8.57
8.95
9.32
Sx_G2[4:0] = 10110
9.54
9.96
10.37
Sx_G2[4:0] = 10111
10.62
11.06
11.51
Sx_G2[4:0] = 11000
11.76
12.27
12.79
Sx_G2[4:0] = 11001
13.02
13.58
14.15
Sx_G2[4:0] = 11010
14.48
15.10
15.72
Sx_G2[4:0] = 11011
16.03
16.71
17.40
Sx_G2[4:0] = 11100
17.72
18.53
19.34
Sx_G2[4:0] = 11101
19.61
20.49
21.37
Sx_G2[4:0] = 11110
21.72
22.70
23.68
Sx_G2[4:0] = 11111
23.85
25.06
26.28
–3 dB, Gain Setting = 11111
120
UNIT
V/V
KHz
ELECTRICAL CHARACTERISTICS
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Offset and Offset TC Compensation
PARAMETER
MIN
TYP
MAX
UNIT
Offset Compensation Low
Offset Setting = 0x000, Stage 1
Gain Setting = 0b000
TEST CONDITIONS
-385
-324
-279
mV
Offset Compensation High
Offset Setting = 0x3FF, Stage 1
Gain Setting = 0b000
279
324
385
mV
Offset Compensation Resolution
Stage 1 Gain Setting = 0b000
0.59
0.72
mV/step
Offset TC Compensation Low
Offset TC Setting = 0x00, Stage 1
Gain Value = 0b000
-371
µV/°C
Offset TC Compensation H igh
Offset TC Settin g= 0x3F, Stage 1
Gain Value = 0b000
361
µV/°C
11.6
µV/V/°C/step
22
°C
Offset TC Compensation Resolution Stage 1 Gain Value = 0b000
Reference Temperature
5.9
Analog to Digital Converter
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
ADC BUFFER FOR 16-BIT AD CONVERTER 1
Gain
DC Level Shift
ADC_BUF bit = 1
DC Offset
1.9
2
2.1
V/V
-1.74
–1.65
-1.55
V
15
mV
-15
ADC BUFFER FOR 10-BIT AD CONVERTER 2
VIN3 Input Voltage Range
0.425
Gain
1.09
DC Offset
-15
1.15
1.7
V
1.21
V/V
15
mV
LSB/V
VIN3 VOLTAGE VERSUS ADC CODE
Gain
(1)
Offset
(1)
760
780
-850
-820
-790
LSB
Gain Temperature Coefficient
Tamb = 25 °C
0.02
LSB/V/°C
Offset Temperature Coefficient
Tamb = 25 °C
-0.02
LSB/°C
Integral Nonlinearity
(1)
740
-1
1
LSB
ADC Code = Gain*VIN3+Offset
5.10 One Wire Interface
PARAMETER
TEST CONDITIONS
Communication Baud Rate
OWI_EN
OWI Enable
OWI_ENhy
OWI Enable Hysteresis
MIN
TYP
MAX
UNIT
2400
115000
Bits Per
Second
6.5
7.0
V
50
mV
10
KΩ
s
Internal Pullup
Activation Signal Pulse Low time
12
Activation Signal Pulse High time
ms
12
ms
OWI_VIH
OWI Transceiver Rx Threshold
0.7 × VDD
VDD + 0.3
V
OWI_VIL
OWI Transceiver Rx Threshold
–0.3
0.3 × VDD
V
OWI_VOH
OWI Transceiver Tx Threshold
VDD = 5 V
OWI_VOL
OWI Transceiver Tx Threshold
VDD = 5 V
0.8
V
8
ELECTRICAL CHARACTERISTICS
4.0
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5.11 Serial Peripheral Interface (SPI) Interface
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VIH
High-level input voltage
0.7 × VDD
VDD + 0.3
V
VIL
Low-level input voltage
–0.3
0.3 × VDD
V
VOH
High-level output voltage
4.0
VOL
Low-level output voltage
fSCK
SPI Frequency
tCSSCK
CS Low to First SCK Rising Edge
25
ns
tSCKCS
Last SCK Rising Edge to CS Rising
Edge
125
ns
tCSD
CS Disable Time
500
ns
tDS
SDI Setup Time
25
ns
tDH
SDI Hold Time
25
ns
tSDIS
SDI Fall/Rise Time
7
ns
tSCKR
SCK Rise Time
7
ns
tSCKF
SCK Fall Time
7
ns
tSCKH
SCK High Time
125
ns
tSCKL
SCK Low Time
125
ns
tSDOE
SDO Enable Time
15
ns
tACCS
SCK Rising Edge to SDO Data Valid
15
tSDOD
SDO Disable Time
tSDOS
SDO Rise/Fall Time
CL(SDO)
Capacitive Load for Data Output
(SDO)
V
0.8
V
4
MHz
ns
3
15
ns
11
ns
10
pF
Figure 5-1. SPI Timing
ELECTRICAL CHARACTERISTICS
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5.12 I2C Interface
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VIH
High-level input voltage
0.7 × VDD
VDD + 0.3
V
VIL
Low-level input voltage
–0.3
0.3 × VDD
V
VOH
High-level output voltage
VOL
Low-level output voltage
fSCL
SCL clock frequency
tSTASU
START condition set-up time
500
ns
tSTAHD
START condition hold time
500
ns
tLOW
SCL low time
1.25
µs
tHIGH
SCL high time
1.25
tRISE
SCL and SDA rise time
7
ns
tFALL
SCL and SDA fall time
7
ns
tDATSU
Data setup time
500
ns
tDATHD
Data hold time
500
ns
tSTOSU
STOP condition set-up time
500
ns
4.0
V
0.8
V
400
KHz
µs
Figure 5-2. I2C Timing
5.13 Non-Volatile Memory
PARAMETER
TEST CONDITIONS
OTP
OTP Number of Erase/Write Cycles
EEPROM
TYP
MAX
8
Erase using UV light
UNIT
KB
10
Cycles
Programmable using SPI or OWI
89
Bytes
Number of bytes writeable by 8051
16
Bytes
EEPROM Erase/Write Cycles
10
MIN
1000
ELECTRICAL CHARACTERISTICS
Cycles
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5.14 GPIO
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VIH
High-level input voltage
RLOAD ≥ 10 kΩ to VDD or to 0 V
0.7 × VDD
VDD + 0.3
V
VIL
Low-level input voltage
RLOAD ≥ 10 kΩ to VDD or to 0 V
–0.3
0.3 × VDD
V
VOH
High-level output voltage
IOH = 1 mA
VOL
Low-level output voltage
IOL = –1 mA
0.8
IOH
High-level output current
VOH = 4.5 V
1
mA
IOL
Low-level output current
VOL = 0.5 V
1
mA
RPU
Pull-up resistance
4.0
V
V
160
kΩ
5.15 DAC1 and DAC2 Output
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Settling time
DAC Code 000h to FFFh
step.Output is 90% of Full Scale.
RLOAD = 5 kΩ, CLOAD = 500 pF
7
µs
Zero scale error
DAC code = 000h, IDAC = 1.5 mA
46
mV
Full scale voltage
Output when DAC code is FFFh,
IDAC = - 1.5 mA
Output current amplitude
DAC Code = 0FFFh , DAC Code =
0000h
Short circuit source current
VDD = 5V, DAC code = 000h
Short circuit sink current
VDD = 5V, DAC code = FFFh
INL (best-fit line)
4.85
4.95
V
1.5
mA
-34
-10
mA
10
34
mA
-3.5
3.5
LSB
MAX
UNIT
5.16 Input Capture and Output Compare
PARAMETER
TEST CONDITIONS
MIN
TYP
INPUT CAPTURE PORTS
VIH
High-level input voltage
RLOAD ≥ 10 kΩ to VDD or to 0 V
0.7 × VDD
VDD + 0.3
V
VIL
Low-level input voltage
RLOAD ≥ 10 kΩ to VDD or to 0 V
–0.3
0.3 × VDD
V
Input capture timer clock frequency
10_20_MHZ bit = 1
10
10_20_MHZ bit = 0
20
Input capture timer bits
MHz
16
Bits
OUTPUT COMPARE PORTS
VOH
High-level output voltage
IOH = 1 mA
VOL
Low-level output voltage
IOL = -1 mA
Output compare timer frequency
VDD – 1.0
V
0.8
10_20_MHZ bit = 1
10
10_20_MHZ bit = 0
20
Output compare timer bits
V
MHz
16
Bits
IOH
High-level output current
1
mA
IOL
Low-level output current
1
mA
ELECTRICAL CHARACTERISTICS
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5.17 Diagnostics
PARAMETER
TEST CONDITIONS
MIN
8051 Software watchdog
MAX
500
Main clock normal operation range
Sensor supply over voltage
VBRG_OV
threshold
VBRG_UV
TYP
Sensor supply under voltage
threshold
UNIT
ms
35
40
45
MHz
3.55
3.65
3.75
V
2.9
3.0
3.11
V
AVDD OV threshold
3.75
3.95
V
AVDD UV threshold
2.72
3.1
V
SensorOV
Output overvoltage threshold for
gain stage 1 and 2
2.4
2.5
2.6
V
SensorUV
Output undervoltage threshold for
gain stage 1 and 2
0.7
.85
1.0
V
f_capHigh
Capacitive sensor interface clock
high frequency fault threshold
1.5
2.5
MHz
f_capLow
Capacitive sensor interface clock
low frequency fault threshold
30
50
kHz
EEPROM CHG PUMP overvoltage
threshold
14.65
V
EEPROM CHG PUMP undervoltage
threshold
11.45
V
DAC loop back voltage gain
0.557
V/V
Open wire leakage current 1 - open
VDD with pull-up on VOUT1
0.537
0.545
2
µA
Open wire leakage current 2 - open
GND with pull-down on VOUT1
20
µA
6 FUNCTIONAL DESCRIPTIONS
In this section, individual blocks in the Section 2 are described in more detail.
6.1
Overvoltage / Reverse Voltage Protection Block
The PGA400-Q1 includes an Overvoltage and Reverse Voltage Protection block. This block protects the
device from overvoltage and reverse-battery conditions on the external power supply. In this block, a
control circuit monitors the input supply line for reverse-battery and overvoltage fault conditions protects
the device if these voltage conditions occur on the external power supply.
6.2
Linear Regulators and Bandgap + Current Blocks
The PGA400-Q1 contains two precision low-drift bandgap supply voltage references for other blocks of the
device. One bandgap provides the reference voltage for internal linear regulators that supply AVDD and
DVDD. The other bandgap reference provides the voltage reference for the all the other internal circuitry,
including sensor supply regulators, sensor offset compensation, etc.
The PGA400-Q1 has two main linear regulators: AVDD Regulator and DVDD Regulator. The AVDD
regulator provides the 3.3 V voltage source for internal analog circuitry while the DVDD regulator provides
the 3.3 V regulated voltage for the digital circuitry. The user needs to connect bypass capacitors of 100nF
on both the AVDD and DVDD pins of the device.
Figure 6-1 shows the Power-On Reset sequence for AVDD and DVDD with respect to the voltage applied
to the VDD pin.
12
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Voltage
5.0V
4.5V
3.3V
2.8V
time
Device Power-up
POR asserted
POR Released
Digital Core Operational
EEPROM
Bank 6
Load = 8us
EEPROM WAIT
Cycle = 12us
Analog Trim Values Valid
M8051w Held in Reset
30us
t1 t2
t3
M8051w Program
Running
t4
VDD Power supply
voltage
t1: POR circuit begins to energize
AVDD, DVDD Regulator
supply voltage
t2: POR circuit reaches DVDD, Digital Core
released from reset
POR Circuit output
voltage
t3: DVDD and POR voltage levels reach
nominal values = 3.3V
t4: VDD reaches nominal voltage level of 4.5V,
all analog circuits operational
Figure 6-1. POR Sequence Diagram
6.3
Internal OSC/XTAL I/F Block
The device includes an internal 40 MHz oscillator, which by default provides the internal clocks required.
The device can also be configured to use an external 40-MHz crystal as a time base via the XTAL_EN bit
in the Sensor Control Register (SENCTRL). When the XTAL_EN bit is set high, the internal 40-MHz
oscillator is disabled and control of the main system clock is driven by the external clock source connected
to the XTAL pin. For more information on programming this device please refer to the PGA400-Q1
Programming Application Note (SLDA015).).
NOTE
Do not use the XTAL pin as an output for sourcing a clock signal to other devices.
6.4
Sensor Voltage Supply Block
The Sensor Voltage Supply block of the PGA400-Q1 supplies both the VBRG output for resistive bridge
sensors and the ICAP supply for capacitive sensors.
6.4.1
VBRG Supply for Resistive Bridges
The VBRG pin on the PGA400-Q1 is a 3.3-V nominal output supply from a linear regulator with a precise
internal temperature independent band-gap reference.
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ICAP Supply for Capacitive Sensors
A functional schematic of the capacitive sensor drive circuit is shown in Figure 6-2. The common node of
the sensor capacitances is tied to the ICAP pin and the current and voltage at this point are referred to as
IX and VX respectively. For the sake of understanding the operation of the drive circuit by itself, the other
terminals of the sensor may be treated as if they were tied to ground, because the sensor signal
measurement circuit regulates the voltage at these nodes. This circuit is essentially a relaxation oscillator
where the capacitance of the sensor, the charging current IC, and the comparator hysteresis VH determine
the frequency of oscillation.
AVDD
IC
S1
Ix
ICAP
Vx
S2
Sensor
CA
CB
VH
+
_
IC
R
R
Figure 6-2. Capacitive Sensor Drive Circuit
To illustrate the circuit operation, the sensor voltage VX is initially set to 0 V. In this state, the positive
terminal of the hysteretic comparator is lower than its negative reference terminal, producing a logical zero
at the output. This results is switch S2 is open and switch S1 is closed, allowing the upper current source
to charge the sensor capacitance. Figure 6-3 shows the resulting waveform. Equation 1 calculates the
linear ramp up slope of the voltage, VX:
dVx
1C
=
dt CA +CB
(1)
After VX is charged up to the high threshold of the comparator, the circuit inverts the states of switches S1
and S2. By closing S2 and opening S1 the lower current source begins to discharge the sensor
capacitances, making VX ramp down with an equal but opposite rate as before. Once VX reaches the low
threshold of the comparator, the circuit again inverts the states of the switches and returns to the positive
charging state. This process of charging and discharging repeats with a period characterized as shown in
Equation 2.
2 •VH
T=
• (CA +CB)
IC
(2)
Both the comparator hysteresis voltage VH and capacitor charging current IC are configurable to allow
control of the oscillation period for a particular sensor. Bits CV[1..0] in the Capacitive Sensor Settings
Register (CAPSEN) can be used to set VH. VH can be set between 100 mV and 700 mV with four possible
steps. Bits CI[2..0] in the Capacitive Sensor Settings Register (CAPSEN) can be used to set IC, with
possible values between 5 µA and 22 µA with eight possible steps. For more information on programming
this device please refer to the PGA400-Q1 Programming Application Note (SLDA015)
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NOTE
For capacitive sensors, one common set of configurations registers are implemented. If
different settings are needed for the two capacitive sensors, then the software must
dynamically update the register values.
IX
IC
t
-IC
Vx
3.3
dVx
dt
T
VH
1.65
0
t
Figure 6-3. Capacitive Sensor Drive Waveforms
6.5
Internal Temperature Block and External Temperature Sensing
The device has the ability to perform temperature compensation via an internal or external temperature
sensor. The user can select the source of the sensor with the TEMP_SEN bit in the Sensor Control
Register (SENCTRL). When the TEMP_SEN bit is set to "0" the internal temperature sensor is used, and
when the TEMP_SEN bit is set to "1" the external temperature sensor is used. For more information on
programming this device please refer to the PGA400-Q1 Programming Application Note (SLDA015)
6.5.1
Internal Temperature Sensor
The device contains an internal temperature sensor which is converted by an ADC and made available to
the 8051 microprocessor so that appropriate temperature compensation algorithms can be implemented in
software. The nominal relationship between the device temperature and the ADC Code is shown in
Equation 3.
ADC Code = 2.8* TEMP -80, TEMP is temperature in °C.
6.5.2
(3)
External Temperature Sensor
The device accepts a temperature from an external temperature sensor via the VIN3 pin. The input
temperature needs to be in the form of a voltage.
NOTE
The Offset TC block has been configured to operate with the internal temperature sensor
transfer function. If an external temperature sensor is used and the user needs to use Offset
TC compensation, then the temperature-to-voltage transfer function of the external
temperature sensor has to match the transfer function of the internal temperature sensor.
6.6
Using the Analog Front End
The PGA400 can be used to interface with Resistive Bridge Sensors as well as Capacitive Sensors. To
enable multiple sensors of either type a series of muxes are used. These muxes are controlled by the
Sensor Control Register (SENCTRL) and Capacitve Sensor Setting Register (CAPSEN).
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The SEN_TYP bit of the Capacitive Sensor Settings Register (CAPSEN) configures the device to be used
with either resisitive or capacitve sensor types. When this bit is set to ‘0’, the device is configured for
capacitive sensors and when the bit is set to "1" the device is configured for resistive bridge sensors.
When either front-end is selected, the other option is disabled and placed in a low quiescent current state.
The Analog Front End (AFE) can also be configured to measure two sensors sequentially. This is
controlled via the SEN_CHNL bit in the Sensor Control Register (SENCTRL). When this bit is set to ‘0’,
the analog MUX at the input of the AFE is switched to pass the signals present at VIN1P and VIN1N pins.
For capacitive sensors, the capacitive sensor drive current is also applied to the ICAP1 pin. When this bit
is set to ‘1’, the VIN2P, VIN2N and ICAP2 pins become active. The SEN_CHNL bit also controls which
External Special Function Registers (ESFRs) are applied to the Stage 1 Gain, Stage 2 Gain, Offset, Offset
TC and the Sign bits.
In addition the sensor supply regulator can be independently enabled or disabled via the VBRG_EN bit in
the Sensor Control Register (SENCTRL). This allows the VBRG 3.3 V output to be used with external
temperature sensors while the AFE is configured in capacitive sensor mode. For more information on
programming the PGA400-Q1 please refer to the
6.7
Stage 1 Gain Block
When the device is configured to interface with resistive sensors, the first gain block that the signal passes
through in the AFE is the Stage 1 Gain block. This gain block is designed with precision, low drift, low
flicker noise amplifiers.
The gain of this stage is adjustable to accommodate sensors with a wide-range of signal spans and can
be set from 3V/V to 51V/V in 8 possible steps. The Stage 1 Gain has two independent registers, Sensor 1
Gain Register (SEN1GAIN) and Sensor 2 Gain Register (SEN2GAIN), so that two different resistive
sensors can be connected with different gain settings. For Stage 1 Gain settings use either the S1_G1 bits
or the S2_G2 bits in the registers mentioned above. The gain setting that is used depends on the
SEN_CHNL bit in Sensor Control Register (SENCTRL). For more information on programming the
PGA400-Q1 please refer to the PGA400-Q1 Programming Application Note (SLDA015).
Table 6-1 outlines the ranges of of resistive bridge sensor characteristics that are compatible.
Table 6-1. Target Resistive Bridge Sensors
PARAMETER
Resistive bridge resistance
CONDITION
–40°C ≤ TA ≤ 150°C
Resistive bridge resistance TC
Resistive bridge offset
(compensated in Analog Front End)
TA = 25°C
Resistive bridge offset TC
(compensated in Analog Front End)
Resistive bridge span
6.8
TA = 25°C
MIN
TYP
MAX
UNIT
2
20
–350
4800
KΩ
–33
33
mV/V
–40
40
µV/V/°C
1.4
75
mV/V
PPM/°C
Self Oscillating Demodulator Block
Figure 6-4 shoes an essential schematic of the capacitive sensor signal measurement circuit. . The
Sensor Voltage Supply block discussed in is depicted only as a functional block called Sensor Drive that
provides the sensor drive current via the ICAPx pin and the clock signals S1 and S2 that are used by the
synchronous demodulator in the measurement circuit. As with the ICAP supply circuitry the demodulator
block circuitry toggles between two states during normal operation. In one state the S1 switches are closed
while the S2 switches are open and in the other state the S1 switches are open while the S2 switches are
closed.
16
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Figure 6-4. Capacitive Sensor Signal Measurement Circuit
To illustrate the operation of the circuit, assume that it has been given sufficient time to settle and is now
operating in its normal steady-state mode of operation. During the positive charging phase, IX is positive
and the S1 switches are closed. In this state, the amplifier seeks to regulate its input terminals to the same
potential, creating a virtual ground at the VINP and VINN pins. This allows Equation 4 to be expresses for
IXas:
dVX
IX =(CA +CB)•
dt
(4)
In a similar manner, Equation 5 describes the currents through CA and CB and the difference between
these currents.
dVX
IA =CA •
dt
(5)
dVX
IB =CB •
dt
(6)
dVX
æ CA-CB ö
DI = (IA - IB) = (CA - CB) ·
= IX · ç
÷
dt
è CA+CB ø
(7)
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The drive current is split between the capacitors in proportion to their relative difference. Measuring ΔI
provides a means to infer the value of the difference in capacitance (CA – CB) or the value of one of the
capacitors if the other is known. Also, driving the sensor with a current source and measuring the resulting
difference in current has the benefit of being fully differential and thus less susceptible to common-mode
disturbances and non-idealities. Note that the expressions for IA and IB may are rewritten in terms of
common-mode and differential-mode components in Equation 8 and Equation 9.
IX
ΔI
IA = +
2
2
(8)
IX
ΔI
IB = 2
2
(9)
The capacitive sensor signal measurement circuit extracts and amplifies ΔI. Figure 6-5 illustrates the
current waveforms at different points in the circuit of Figure 6-4. The currents into and out of the sensor
are shown on axis (a). Initially, the circuit is in the discharge phase where IX is negative and S2 switches
are closed. After some time, the state switches to the charge phase where the S1 switches are closed.
This process of changing the state of the circuit continues periodically with a frequency set by the sensor
drive circuit.
During each half cycle the IX current is split into the individual capacitor currents IA and IB. As shown in
Figure 6-5(b), while the S1 switches are closed I2 = IA and I1 = IB, but when the S2 switches are closed the
currents are inverted such that I2 = IB and I1 = IA. Because the sign of IX is also changing, the difference
between I2 and I1 remains constant and equal to ΔI (ignoring the glitches that occur at phase transitions).
While the S1 switches are closed, half the sensor drive current (IC/2) is subtracted from I2 and I1 and while
the S2 switches are closed, half the sensor drive current is added to them. This removes the cycle-to-cycle
offset in Figure 6-5(b), delivering the DC currents IP and IN to the trans-impedance amplifier, as shown in
Figure 6-5(c) where IP – IN = ΔI. For low frequency signals, the output voltage of the amplifier is shown in
Equation 10.
æ CA - CB ö
Vout = R ò •ΔI = R ò• I C• ç
÷
è CA + CB ø
(10)
For a given sensor, the drive current IC should be adjusted to keep VOUT < 1.65 V over the expected
operating conditions of the sensor to avoid saturating the ADC input.
NOTE
for some types of wide span sensors, it may be necessary to reduce the gain set by the
value of Rf in the transimpedance amplifier. The drive current IC and feedback resistance Rf
can be adjusted via Capacitive Sensor Settings Register (CAPSEN). For more information on
programming the PGA400-Q1 please refer to the PGA400-Q1 Programming Application Note
(SLDA015).
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(a)
IX
IA
IB
IC
IC/2
-IC/2
-IC
I2
(b)
I1
IC/2
-IC/2
(c)
IP
IC/2
IN
-IC/2
Figure 6-5. Current Waveforms in the Sensor Signal Measurement Circuit
This process of changing the state of the circuit continues periodically with a frequency set by the sensor
drive circuit described in Equation 11.
IC
f=
2 •VH • (CA + CB)
(11)
BEcause the op-amp must settle at each switching cycle, there is an upper bound imposed on the sensor
drive frequency. Using a minimum half-cycle time of seven times the op-amp settling time and a minimum
op-amp GBW of 7 MHz, shows the following upper bound on the switching frequency:
ƒMAX ≤ 800 kHz
In reality, there are glitches and residual up-converted noise in the IP and IN signals. For this reason, the
trans-impedance amplifier has a low-pass characteristic, with one pole set by the feedback elements Rf
and Cf, and a second pole at the output set by R and the same capacitance Cf. For most sensor types, R
is equal to Rf. In this case, the frequency dependent trans-impedance may be expressed as shown in
Equation 12.
Rf
Z(s) =
W
1 + s • Rf • Cf) 2
(12)
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Where with nominal values of Rf = 625 kΩ and Cf = 16 pF, the corner frequency of the filter is 15.9 kHz. If
the minimum permissible ripple suppression is chosen to be 40 dB at the switching frequency, and the
corner frequency is rounded up to 20 kHz, illustrates the lower bound on the switching frequency:
ƒmin ≥ 200 kHz
For a given sensor, the drive circuit comparator hysteresis value VH and the drive current IC should be
chosen so that the switching frequency remains within the range of 200 to 800 kHz as the sensor
capacitance varies within its expected range.
Table 6-2 outlines the ranges of compatible capacitive bridge sensor characteristics.
Table 6-2. Target Capacitive Sensors
PARAMETER
CONDITION
Capacitive sensor initial capacitance
(Cp+Cr)
Capacitive sensor offset
(compensated in Analog Front End)
(Cp,0 – Cr,0)/(Cp,0 + Cr,0)
Capacitive sensor span
(Cp,100 – Cr,100)/(Cp,100 + Cr,100)
MIN
MAX
UNIT
10
310
pF
–0.16
0.16
0.04
1.00
Capacitive sensor offset TC
6.8.1
0.8
%Cv,0/
°C
Configuring the Capacitive Sensor Interface for a Particular Sensor
A general procedure for choosing what values to use for the capacitive sensor drive current (IC), drive
voltage comparator hysteresis (VH) and trans-impedance (Rf) is the following:
• Find the values of IC that maintain VOUT below 1.65 V for the maximum sensor span plus offset
• Using the largest allowed value for IC and the minimum and maximum total sensor capacitance
(CA+CB), find a value for VH that maintains the switching frequency within the range of 200 kHz to 800
kHz
• If the frequency constraints cannot be met, reduce the value of IC and iterate to find an optimal solution
This procedure can be applied to configure the capacitive sensor interface with total capacitances ranging
from 10 pF to 300 pF and span plus offset ratios (CA–CB)/(CA+CB) up to 0.36.
The Stage 1 gain has two independent registers for the two sensors that can be potentially connected.
The Stage 1 gain setting used depends on the SEN_CHNL bit in the Sensor Control Register. For more
information on programming the PGA400-Q1 please refer to the the PGA400-Q1 Programming Application
Note (SLDA015).
6.9
Sign Bit Block
The device has a sign bit block that is used for span sign compensation. This block is used to change the
polarity of the first stage output, and it is implemented through the use of four switches. The switches are
set through the use of the S1_INV bit for sensor 1 and the S2_INV bit for sensor 2 in the Sensor Control
Register (SENCTRL). There are two independent sign bit settings to accommodate configuring the polarity
for two independent sensors. The sensor sign bit used is based on the SEN_CHNL bit in the Sensor
Control Register. For more information on programming the PGA400-Q1 please refer to the the PGA400Q1 Programming Application Note (SLDA015).
6.10 Offset and Offset TC Compensation Blocks
The offset compensation circuit can be configured to null out the sensor offset and first order offset
temperature coefficient. The offset compensation block is located between the Sign Bit block and the
Stage 2 Gain block as shown in the Section 2.
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The offset compensation, VCOMP, is a value that is subtracted from the output of the sign bit block. This
offset provides a means to null the sensor offset prior to Stage 2 Gain. The offset compensation circuit
block provides ten bits of zero-order compensation and six bits of first-order TC compensation.
A more detailed block diagram of the offset compensation subsystem is shown in Figure 6-6. As shown
Vcomp is derived from two references, VBG and VPTAT. Where VBG is a precise temperature independent
band-gap reference voltage, and VPTAT is a proportional-to-absolute-temperature voltage. In PGA400-Q1,
the gains in the offset compensation circuitry (A, B, C) have been designed assuming the following
characteristics about the reference signals:
VBG = 1.23 V
VPTAT (T) = kPTAT ● (T + 273) + ξPTAT
(13)
(14)
where
kPTAT = 3.7 mV/°C and ξPTAT = –47 mV
(15)
NOTE
If an external temperature sensor is used, the signal applied to the VIN3 pin must have the
same temperature dependency as the above mentioned VPTAT signal or else the offset TC
compensation does not work as intended.
VBG
A
10
Vcomp,0
Vcomp
+
A1
2m+1-2
-
Vcomp,1
6
B
2n+1-2
C
2n+1-2
VPTAT
6
+
Figure 6-6. Block Diagram of Offset Compensation Circuit
The zero-order portion of VCOMP is produced by scaling VBG by the gain A to generate the reference for a
10-bit DAC. The DAC scales this reference by 2m+1–210, where m is decimal equivalent of the DAC’s
digital input and ranges from 0 to 1023. The zero-order portion of the compensation voltage is expressed
as a function of m as shown in Equation 16.
VCOMP,0 (m) = VBG ● A ● (2 ● m + 1 – 210) V
(16)
The first order portion of VCOMP is constructed from the difference between scaled versions of VPTAT and
VBG. The reason for this is that the temperature compensation signal should pivot about a particular
reference temperature, which ideally would be the same temperature at which the zero-order portion of
the sensor offset is calibrated out. Because VPTAT pivots about 0 K, a temperature independent offset must
be introduced to shift the pivot temperature up to a practical value like 22°C. The first-order portion of the
compensation voltage is expressed in Equation 17.
Vcomp,1 (n,T) = (C ● [kPTAT ● (T + 273) + ξPTAT] – B ● VBG) ● (2 ● n + 1 – 26) V
(17)
Where the reference temperature about which this function pivots may be expressed in terms of the other
variables as shown in Equation 18.
1
æV • B
ö
TR =
• ç BG
-ε PTAT ÷- 273°C
kPTAT è C
ø
(18)
The gains B and C are set to produce a reference temperature of approximately 22°C.
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When Equation 17 and Equation 18 are combined and consolidate the values of the constants, the final
output voltage of the offset compensation circuit is expressed as a function of m, n, T, and A1 in the
following way:
1277
Vcomp (m, n, T, A1) = A1•
• [250 • (2 • m + 1 - 210) + 4.921 • (T-22) g (2 • n + 1 - 26)] nV
3
(19)
For resistive sensors, the gain used for the offset compensation calculation is always the same as the first
stage gain in the AFE and is controlled by the same registers. For capacitive sensors, A1 is an
independent variable that may be set to meet a specific sensor or noise requirements.
NOTE
The above voltage Vcomp is subtracted (differentially) from the output of the first stage.
The Offset and Offset TC has two independent registers, Sensor 1 Offset Register (SEN1OFF1 and
SEN1OFF2) and Sensor 2 Offset Register (SEN2OFF1 and SEN2OFF2), to accomodate for two
independent sensors that can be potentially connected. The sensor offset value used is based on the
SEN_CHNL bit in the Sensor Control Register (SENCTRL). For more information on programming the
PGA400-Q1 please refer to the PGA400-Q1 Programming Application Note (SLDA015).
6.11 Stage 2 Gain Block
The Stage 2 Gain block is contructed with a low flicker noise, low offset amplifier. Both resistive bridge
sensors and capacitive sensors share this gain stage. The gain setting for this stage ranges from 1 V/V to
25 V/V in 32 possible steps.
The Stage 2 Gain block has two independent registers, Sensor 1 Gain Register (SEN1GAIN) and Sensor
2 Gain Register (SEN2GAIN). This accomodates two different sensors that can be connected with
different gain settings. The Stage 2 gain is determined by the SEN_CHNL bit in Sensor Control Register.
For more information on programming the PGA400-Q1 please refer to the PGA400-Q1 Programming
Application Note (SLDA015).
6.12 ADC Buffer Blocks
The device has two buffer blocks, one for the pressure signal path and one for the temperature signal
path.
6.12.1 Analog to digital Converter Buffer 1
The ADC Buffer 1 is a differential amplifier with 2X gain that is used to condition the pressure signal
before reaching the Analog to Digital Converter (ADC).
In addition to gain this block can be configured to provide a level shift using the ADC_BUF bit in Sensor
Control Register (SENCTRL). When this bit is set to ‘0’, no offset is introduced to the signal, and the
output of the ADC buffer is simply two times the output of Gain Stage 2. When this bit is set to ‘1’, a –1.65
V offset is introduced such that the output of the ADC buffer is equal to two times the output of Gain Stage
2 minus 1.65 V. The Level Shift feature of the ADC Buffer shifts the output of the Stage 2 Gain so that the
full dynamic range of the sigma-delta modulator can be used.
6.12.2 Analog to digital Converter Buffer 2
The ADC Buffer 2 is a unity gain differential amplifier. This buffer block conditions the temperature signal
before reaching the ADC.
6.13 Sigma Delta Modulator Blocks
There are two independent Sigma Delta Modulator ADCs, one for the pressure signal and another for the
temperature signal.
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6.13.1 Sigma Delta Modulator for AD Converter 1
The Sigma Delta Modulator 1 block is a 1-bit 1MHz sigma-delta modulator for the pressure sensor signal.
To further condition the signal this stage is followed by two stages of digital decimation filters.
6.13.2 Sigma Delta Modulator for AD Converter 2
The Sigma Delta Modulator 2 block is a 1-bit 128kHz sigma-delta modulator for the temperature signal.
The input signal to the sigma-delta modulator can come from either the internal or external temperature.
The output of this ADC is followed by a single decimation filter.
6.14 Decimation Filter Blocks
The device contains three Signal Decimation FIlters. Two back to back decimation filters for the pressure
sensor signal path and one decimation filter for the termperature path.
6.14.1 ADC1 Decimation Filter Blocks
The sensor signal path contains two decimation filters in series with each other. The first decimation filter
has a fixed decimation ratio and a second decimation filter that has a variable decimation ratio.
The 1st Stage Decimator Filter has a fixed decimation ratio of 32. Based on the 1MHz sampling frequency
of the sigma-delta modulator, the output rate of the 1st stage decimator is fixed at 32 µs per sample.
The 2nd Stage Decimator has a variable decimation ratio. This filter further decimates the output of the
first stage decimator. The decimation ratios of the second stage can be configured for a decimation ratio
of 2, 4, or 8 using the OSR[1..0] bits in the Decimator and Low Power Control Register (DECCTRL). For
more information on programming the PGA400-Q1 please refer to the PGA400-Q1 Programming
Application Note (SLDA015).
The output of the second decimation filter in the sensors signal path is a 16 bit signed value. Some
example second stage decimation output codes for given differential voltages at the input of the sigma
delta modulator are shown in Table 6-3:
Table 6-3. Input Voltage to Output Counts for the
Signal Channel ADC
SIGMA DELTA MODULATOR
DIFFERENTIAL INPUT VOLTAGE
NOISE-FREE OUTPUT
–3.3V
–32768
–1.65V
–16384
0
0
1.65V
16383
3.3V
32767
6.14.2 Decimation Filters for AD Converter 2
The temperature path contains one fixed ratio decimation filter block after the sigma delta modulator. The
filter is 10-bit with fixed decimation ratio of 1024. Based on the 128-kHz sampling frequency, the output
rate of the fixed ratio decimation filter is fixed at 8 ms per sample.
The output of the temperature channel decimation filter is a 10 bit signed value. The equation to calculate
the relationship between the input voltage at VIN3 and the output of the decimator block is shown below.
ADC Code = 760* VIN3 -820, VIN3 is voltage at the input of the buffer in volts.
(20)
Table 6-4 summarizes the relationship between the internal temperature sensor and the decimator output.
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Table 6-4. Input Voltage to Output Counts for the
Temperature Channel ADC
NOISE-FREE OUTPUT OF
TEMPERATURE CHANNEL
DECIMATOR
INTERNAL TEMPERATURE
–40°C
-196
–20°C
-140
0°C
-83
20°C
-27
40°C
28
150°C
338
6.14.3 Accessing the ADC Values for the 8051
the ADC Decimator Output Register (ADCMSB and ADCLSB) makes available the output of all three
decimators that are available to the microprocessor.
The microprocessor specifies which decimator is loaded by writing a "1" to the appropiate bit in the Load
ADC Decimator Shadow Register (LD_DEC).
If more than 1 bit in the LD_DEC register is set to 1 simultaneously, then only one decimator output is
loaded into ADCMSB and ADCLSB register. The priority used to determine which decimator output gets
loaded is as follows:
• Decimator 1 Output
• Decimator 2 Output
• Temperature Decimator
For more information on programming the PGA400-Q1 please refer to the PGA400-Q1 Programming
Application Note (SLDA015).
6.15 8051 WARP Microprocessor Block
The 8051 WARP microprocessor is an exceptionally high-performance version of this popular 8-bit
microcontroller, requiring only 2 clocks per machine cycle rather than the 12 clocks per cycle of the
industry standard device while it maintains functional compatibility with the standard device
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Figure 6-7. 8051W Core. The 8051W core includes two 16-bit timers and serial interface.
6.16 Digital Interface
The digital interfaces are used to access (read as well as write) the internal memory spaces described in
Section 6.20. Each interface uses different pin(s) for communication. The device has three separate
modes of communication:
1. One-Wire Interface (OWI)
2. Serial Peripheral Interface (SPI)
3. Inter-Integrated Circuit (I2C)
Each communication mode has its own protocol of communication, but all three access the same memory
elements within the device. For all three communication modes the PGA400-Q1 device operates as a
slave device.
Figure 6-8 shows the interface between the 8051W, the Memory block and the Digital Interface. In the
PGA400-Q1, only the Digital Interface OR the 8051W can access can access the internal memory
spaces. It is not possible for both 8051W and the Digital Interface to access the memory spaces
simultaneously. Therefore there is an access selection bit called IF_SEL in the Micro/Interface Control
Register (MICRO_IF_SEL_T) that allows either the 8051W microprocessor or the digital interfaces to have
access to the OTP, EEPROM, ESFR and RAM memory spaces.
Figure 6-8 also shows that a special memory space called the Test Registers are only accessible only via
the Digital interface. Since the Micro/Interface Control Register is in the Test Register memory block which
is only accessible via the digital interface, only the digital interfaces can change the memory access
selection.
To select the specific digital interface that is used for communication the DI_CTRL[1:0] bits in the Digital
Interface Control Register (DI_CTRL) need to be set. If DI_CTRL is configured for I2C, then GPIO1 and
GPIO3 automatically configures for I2C operation.
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Figure 6-8. Digital Interface
NOTE
If Digital Interface is used to access the internal memory, the 8051W must enter reset state
(to prevent the 8051W from accessing the memory. The 8051W operates in reset state using
the "MICRO_RESET" bit in the Micro/Interface Control Register (MICRO_IF_SEL_T).
NOTE
The internal memory space internal is accessible via the Digital Interface without the need for
the user to implement any communication software in the 8051W. The user must implement
communication software, in the form of an interupt service routine, only if the user wishes to
communicate with the PGA400-Q1 while 8051W is not in reset state. This interupt service
routine is used in conjuction with a communication buffer interface, that is available in both
the ESFR and Test Memory address spaces.
NOTE
While the 8051W is not in a reset state, it transfers data to the internal memory space using
the Digital Interface. This transfer is accomplished using the communication buffer that exists
between the Test Register memory space and the ESFR memory space (shown as COMM
BUFFER in Figure 6-8).
6.17 One-Wire Interface (OWI)
The device includes a One-Wire Interface (OWI) digital communication interface. The main function of the
OWI is to enable writes to and reads from all addresses available for OWI access. These include access
to most Test Register and ESFR memory locations.
6.17.1 Overview of OWI Interface
The OWI digital communication is a master-slave communication link in which the PGA400-Q1 operates
as a slave device only. The master device controls when data transmission begins and ends. The slave
device does not transmit data back to the master until it is commanded to do so by the master. A logic 1
(high) value on the one wire interface is defined as a recessive value, while a logic 0 (low) value on the
one-wire interface is defined as a dominant value.
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The VOUT1/OWI pin acts as both an analog DAC output and the interface communication pin, so that
when the device is embedded inside of a system module only three pins are needed (VOUT1/OWI pin,
VDD and GND). The 8051 microprocessor has the ability to control the activation and deactivation of the
OWI interface based upon the signal driven into the VOUT1/OWI pin.
During normal operation the DAC is the last stage of the sensor signal path, and drives data out on the
VOUT1/OWI pin in the form of an analog signal. To change to OWI communication mode this pin must be
driven with an appropiate activation signal described in Section 6.17.2.
Figure 6-9 shows a functional equivalent circuit for the structure of the OWI and DAC circuitry.
Figure 6-9. OWI System Components
6.17.2 Activating and Deactivating the OWI Interface
6.17.2.1 Activating OWI Communication
If the device is operating in the normal operation where the DAC is active and I2C or SPI communication
modes are not enabled the following activation signal can be driven into the VOUT1/OWI pin to place it
into OWI communication mode. The process begins with driving the OWI_EN voltage on the VOUT1/OWI
pin. As soon as the DAC voltage exceeds 5.4 volts the DAC is switched off by by a comparator. Once the
pin voltage reaches the OWI_EN voltage threshold a deglitch timer begins. Once the pin voltage has been
asserted for a time greater than the deglitch time the OWI Activation Comparator transmits a logic 1 value
to the OWI Controller.
This deglitch time is set by the OWI_DEGLITCH_SEL bit in the Digital Interface Control Register
(DI_CTRL), and has the following properties:
• OWI_DEGLITCH_SEL = ‘0’ → OWI Activation deglitch time = 1ms
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OWI_DEGLITCH_SEL = ‘1’ → OWI Activation deglitch time = 10ms
The default value for OWI_DEGLITCH_SEL bit is ‘0’, which corresponds to deglitch time of 1ms.
When the high voltage has been maintained for the proper deglitch time, the pin must then be driven back
to the standard 5V IO voltage for an additional deglitch time set by the same bit as before. During this
second deglitch time the DAC becomes active again only until the the second deglitch time has passed.
Once this second deglitch period is over the OWI controller generates an OWI activation interrupt that is
sent to the 8051. This user interrupt service routine switches the VOUT1/OWI pin's mode by writing to the
appropriate registers. The OWI transceiver is switched to the VOUT1/OWI pin and the DAC is placed back
into the OFF state. The capability to drive the appropiate OWI_EN voltage must be provided in the test
environment.
The XCVR switch, controlled by an ESFR register, changes the output drive from the unidirectional DAC
analog signal to the bi-directional OWI digital signal interface. Once this switch is selecting the OWI
transceiver, OWI data can be transmitted and received through the VOUT1/OWI pin. The OWI transceiver
is responsible for translating voltage levels to appropriate logic levels so that the OWI controller may
process the OWI data. The OWI_REQ deglitch filter ensures that no invalid activation signals are
transmitted from the analog OWI Activation Comparator to the 8051 interrupt input. Both the DAC switch
ESFR and the XCVR switch ESFR must be set via the OWI interrupt service routine. It is recommended to
set the DAC switch to the OFF position before setting the XCVR switch to the OWI mode.
If the device is already in SPI communication mode or I2C communication mode, enabling OWI
communication changing the DAC enable bit and the OWI transceiver enable bit in the Digital Interface
Control Register (DI_CTRL) is the only requirement. The register bits can be set manually in the following
order.
1. The register bits DI_CTRL[1:0] in the Digital Interface Control Register (DI_CTRL) need to be set to
0b10. This activates the OWI controller and deactivates the DAC via the DAC switch.
2. The OWI_XCR_EN bit in the Digital Interface Control Register (DI_CTRL) must be set to 1. This turns
on the OWI transceiver and switches the VOUT1/OWI pin to the OWI transceiver.
NOTE
Note that DI_CTRL[1:0] and OWI_XCR_EN bits can be written simultaneously (in 1 write
command). However, because the state of the VOUT1/OWI is unknown during the transition
from VOUT1 to OWI, it is recommended that the master wait at least 15 ms before
transmitting the OWI command.
6.17.2.2 Deactivating OWI Communication
In order to deactivate the OWI communication the following two steps must be performed in any order.
• The OWI_XCR_EN bit in the Digital Interface Control Register (DI_CTRL) must be set to 0. This turns
off the OWI transceiver and switch the VOUT1/OWI pin to the DAC driver.
• The register bits DI_CTRL[1:0] in the Digital Interface Control Register (DI_CTRL) must to be a value
other than 0b10. This selects a different Digital Interface (either I2C or SPI) and it also switchs on the
DAC driver.
6.17.3 OWI Communication Error Status
The device has the ability to detect and report errors in OWI communication. The OWI Error Status 1
Register (OWI_ERR_1), and OWI Error Status 2 Register (OWI_ERR_2) contain the error bits. The
communication errors that are reported with the registers include
• Out of range communication baud rate
• Invalid SYNC field
• Invalid STOP bits in command and data
• Invalid OWI command
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For more information on OWI protocol, operation, avaialble commands and example communication refer
to the PGA400-Q1 Programming Application Note (SLDA015).
6.18 Serial Peripheral Interface (SPI) Interface
The device includes a Serial Peripheral Interface (SPI) digital communication interface. The main function
of the SPI is to enable writes to and reads from all addresses available for SPI access.
6.18.1 Overview of SPI Interface
SPI is a synchronous, serial, master-slave, communication standard that requires the following four pins:
• SDI: SPI slave in master out, serial input pin.
• SDO:SPI slave out master in, serial output pin (tri-state output)
• SCK: SPI clock which controls the communication.
• CS: chip select (active low)
SPI comminucates in a master/slave style where only one device, the master, can initiate data
transmissions. The PGA400-Q1 always acts as the slave in SPI communication, where whatever external
device that is communicating to it becomes the master mode. Both devices begin data transmission with
the most significant bit (MSB) first.
Because multiple slave devices can exist on one bus, the master node is able to notify the specific slave
node that it is ready to begin communicating with by driving the CS line to a low logic level. In the absence
of active transmission, the master SPI device places the device in reset by driving the CS pin to a high
logic level. During a reset state the SDO pin operates in tri-state mode. For the SPI interface to have
access to memory locations other than test register space, the IF_SEL bit in the Micro/Interface Control
Test register (MICRO_IF_SEL_T) has to be set to ‘1’.
6.18.2 Activating the SPI Interface
To activate SPI communication the following steps must be made in order:
1. Place the 8051W in reset by setting the MICRO_RESET bit in the Micro/Interface Control Register
(MICRO_IF_SEL_T) to logic "high"
2. Give control of the memory block to the digital interface by setting the IF_SEL bit in the Micro/Interface
Control Register (MICRO_IF_SEL_T)to logic "high"
3. Set the DI_CTRL bits in the Digital Interface Control Register (DI_CTRL) to 0b00 for SPI interface
6.18.3 Clocking Details of SPI Interface
Input data on the SDI pin must be valid on the rising edge of the SCK clock, whereas output data on the
SDO pin changes during the rising edge of the SCK clock. For SPI timing information the SPI Timing
diagram is shown in Figure 5-1.
For more information on SPI protocol, operation, avaialble commands and example communication refer
to the PGA400-Q1 Programming Application Note (SLDA015).
6.19 Inter-Integrated Circuit Interface
The device includes an Inter-Integrated Circuit (I2C) digital communication interface. The main function of
the I2C is to enable writes to, and reads from, all addresses available for I2C access.
6.19.1 Overview of I2C Interface
I2C is a synchronous serial communication standard that requires the following two pins for
communication:
• GPIO_1/IC_1/SDA: I2C Serial Data Line (SDA)
• GPIO_3/OC_1/SCL: I2C Serial Clock Line (SCL)
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I2C communicates in a master/slave style communication bus where one device, the master, can initiate
data transmission. The device always acts as the slave device in I2C communication, where the external
device that is communicating to it acts as the master node. The master device is responsible for initiating
communication over the SDA line and supplying the clock signal on the SCL line. When the I2C SDA line
is pulled low it is considered a logical zero, and when the I2C SDA line is floating high it is considered a
logical one. For the I2C interface to have access to memory locations other than test register space, the
IF_SEL bit in the Micro/Interface Control Test register (MICRO_IF_SEL_T) has to be set to logic one.
6.19.2 Activating the I2C Interface
To activate I2C communication the following steps must be made in order:
1. Place the 8051W into a reset state by setting the MICRO_RESET bit in the Micro/Interface Control
Register (MICRO_IF_SEL_T) to logic "high"
2. Give control of the memory to digital interface by setting the IF_SEL bit in the Micro/Interface Control
Register (MICRO_IF_SEL_T)to logic "high"
3. Set the DI_CTRL bits in the Digital Interface Control Register (DI_CTRL) to 0b01 for I2C interface
6.19.3 Clocking Details of I2C Interface
The device samples the data on the SDA line when the rising edge of the SCL line is high, and is changed
when the SCL line is low. The only exceptions to this indication a start, stop or repeated start condition as
shown in Figure 6-10
SDA
acknowledgement
signal from slave
MSB
acknowledgement
signal from receiver
byte complete,
interrupt within slave
clock line held low while
interrupts are serviced
SCL
S
or
Sr
1
2
7
8
9
1
SCK
2
3-8
SCK
START or
repeat START
condition
STOP or
repeated START
condition
SDA
SDA
SCL
SCL
START condition
30
Sr
or
P
9
STOP condition
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SDA
SCL
START
condition
1-7
8
9
ADDRESS
R/W
ACK
1-7
DATA
8
9
ACK
1-7
8
DATA
9
ACK
STOP
condition
Figure 6-10. I2C Clocking Details
For more information on I2C protocol, operation, avaialble commands and example communication refer to
the PGA400-Q1 Programming Application Note (SLDA015).
6.20 Memory
6.20.1 OTP Memory
The OTP Memory space is 8 kB and is located at memory pages 3 and 4. This memory space contains
program instructions for the 8051W microprocessor. To program the OTP memory an external VP_OTP
voltage needs to be applied to the VP_OTP pin.
The device has the ability to lockout access to all memory spaces except the Test Register space from the
digital interface. This helps protect firmware intellectual property. The locking/unlocking of the access to
the OTP memory is achieved using 8051W Port 0 in the SFR memory space (P0[7:0]) in the following
way:
• If P0(7:0) is set to 0xAA, the Digital Interface is in locked state. In this state, memories cannot be read
via Digital Interface. Note that once the Digital Interface is locked, the Micro/Interface Control Test
register is also not accessible via the Digital Interface.
• If P0(7:0) is set to 0x00 while the Digital Interface is in locked state, then the memories are accessible
via Digital Interface.
The 8051W microprocessor can access all memories even when the memories are in locked state,
allowing software programs to execute. If the Digital Interface is in locked state and the CPU watchdog
causes a 8051W reset, the Digital Interface maintains the lockout state.
6.20.2 EEPROM Memory
Figure 6-11 shows the EEPROM Bank structure. EEPROM cells within a bank are activated only when
reading from or writing to their specific EEPROM bank. Therefore the contents of each EEPROM must be
transferred to the EEPROM Cache before reads and writes can occur to that bank. There are a total of six
banks of EEPROM, and they are located at memory page 5.
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BANK_SEL[2:0]
IF_SEL
BANK0_EE_DATA [127:0]
EEPROM
PROGRAM
DATA _Out[127:0]
XRAMA[3:0]
XRAMDO[7:0]
8051
Microprocessor
Cache Read
Data_out[7:0]
Digital Interface
SPI
I
n
t
e
r
f
a
c
e
BANK1_EE_DATA [127:0]
Cache
Address[3:0]
EEPROM
Read
DATA _IN[127:0]
EEPROM
Cache
(16 Bytes)
DI_Address[3:0]
DI_Data_out[7:0]
M
u
x
EEPROM
Bank 0
(128-bits)
EEPROM
PROGRAM
DATA _Out[127:0]
Cache Write
Data_In[7:0]
E
E
P
R
O
M
B
a
n
k
EEPROM
PROGRAM
DATA _Out[127:0]
EEPROM
Bank 1
(128-bits)
BANK2_EE_DATA [127:0]
EEPROM
PROGRAM
DATA _Out[127:0]
EEPROM
Bank 2
(128-bits)
BANK3_EE_DATA [127:0]
I2C
S
e
l
e
c
t
Cache Read
Data_out[7:0]
OWI
M
u
x
EEPROM
PROGRAM
DATA _Out[127:0]
EEPROM
Bank 3
(128-bits)
BANK4_EE_DATA [127:0]
EEPROM
PROGRAM
DATA _Out[127:0]
EEPROM
Bank 4
(128-bits)
BANK5_EE_DATA [72:0]
EEPROM
PROGRAM
DATA _Out[127:0]
EEPROM
Bank 5
(72-bits)
Figure 6-11. Structure of EEPROM Interface
6.20.2.1 EEPROM Memory Organization
6.20.2.1.1 EEPROM Cache
The EEPROM Cache serves as temporary storage of data being transferred to/from a selected EEPROM
bank. Data transferred to the EEPROM cache from either a digital interface or from the M8051 is byte
addressable and one byte at time can be written to or read from. The only exception being a special OWI
burst write/read access in which 8 bytes of data can be accessed at a time. Selection of the EEPROM
Cache interface is determined by the IF_SEL bit in the EEPROM Access Control register.
Data transferred to the Cache from an EEPROM bank is loaded 128-bits at a time during the EEPROM
Cache load cycle. EEPROM Bank selection is determined by the value placed in the BANK_SEL bits in
the EEPROM Access Control Register. When programming an EEPROM bank, the EEPROM Cache
holds the programming data for the amount of time necessary to complete the EEPROM programming
process.
6.20.2.1.2 Bank 0
Bank 0 is used for storage of customer data and is the only bank which can be programmed by both the
8051W and the Digital Interface. 16 bytes of EEPROM data are provided in bank 0. No CRC validation
against a pre-stored CRC value occurs when Bank 0 is programmed, and thus, there are no dedicated
EEPROM Cells used for CRC storage.
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Due to limited number of erase/write cycles, the user has to keep track of the number of writes to
EEPROM Bank 0 and store the value inside the bank because it is the only bank that is accessable when
the write is occuring.
6.20.2.1.3 Banks 1-4
Banks 1–4 are used for storage of customer data. Each bank 1 through 4 provides 128-bits of data
storage for a total of 512 bits (64 bytes) of storage data. Since the 8051W does not have access to these
banks, only the digital interfaces can program them. Each time one of these banks is programmed a CRC
is calculated based upon the data held in the EEPROM Cache during program. This calculated CRC value
is stored internally and validated after bank programming is complete.
6.20.2.1.4 Bank 5
The firse 64-bits (8 bytes) of Bank 5 are provided to the customer for calibration value and/or general
storage. Byte 9 is used for the storage of the cummulative CRC values for banks 1-4 and the first half of
Bank 5. When programming Bank 5 it is required to place the cumulative CRC value for banks 1–5 in the
EEPROM Cache Address 0x558. This CRC value covers all data in banks 1 through 4 and the first 64-bits
of data in bank 5. Everytime programming of Bank 5 is completed the CRC value is validated. The
remaining 7 bytes of Bank 5 (0x559 - 0x55F) are not used.
6.20.3 RAM Memory
This memory space is used for 8051W scratchpad memory, such as intermediate calculation results. It is
a 256 byte memory space, and located at memory page 1.
6.20.4 SFR/ESFR Memory
The 8051W uses two types of memory storage, Special Function Registers (SFR) and External Special
Function Registers (ESFR). The SFR registers are used for 8051W internal operations, and cannot be
accessed external to the 8051W. The ESFR register exists on the same address space as the SFR,
however these registers can be accessed via the digital interface. The ESFR registers are used for
calibration, configuration, fault reporting and memory storage. The SFR/ESFR total memory space is 256
bytes, and they are located at memory page 2.
6.20.5 Test Register Memory
The test register memory space is used for diagnostic configuration, and testing for sensor calibration. The
test registers are located at memory page 0, and can only be accessed by the Digital Interface.
6.21 General Purpose Input Output (GPIO) Pins
The GPIO_x pins have multiple functions, including general purpose inputs/outputs (GPIO), input capture,
output compare or I2C. In the GPIO mode, the GPIO_x pins are connected directly to 8051W port pins.
The state of the pins can then be controlled through software by setting the appropriate I/O port SFRs in
the 8051W. Table 6-5 shows the mapping of the GPIO_x pins to specific 8051W ports.
6.21.1 Setting the GPIO Functions
Table 6-5. GPIO_x Pin Functionality
8051W
PORT
PIN
GPIO_1/IC_1/SDA
GPIO_2/IC_2
ALTERNATE
FUNCTION 1
ALTERNATE
FUNCTION 2
2.0
Input Capture 1
I2C Data
Default
Set IC1_ACT to 1
in IC_OC_GPIO
Set DI_CTRL[1:0]
= 0b01 in DI_CTRL
2.1
Input Capture 2
-
Default
Set IC2_ACT to 1
in IC_OC_GPIO
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Table 6-5. GPIO_x Pin Functionality (continued)
8051W
PORT
PIN
GPIO_3/OC_1/SCL
GPIO_4/OC_2
GPIO_5
ALTERNATE
FUNCTION 1
ALTERNATE
FUNCTION 2
2.2
Output Compare 1
I2C Clock
Default
Set OC1_ACT to
1 in IC_OC_GPIO
Set DI_CTRL[1:0]
= 0b01 in DI_CTRL
2.3
Output Compare 2
Default
Set OC2_ACT to
1 in IC_OC_GPIO
3.2
-
-
Default
After power up or reset, the default configuration for all of these pins is the input GPIO function. To
change the function of a pin a write command to the appropriate ESFR will automatically reconfigure it.
Table 6-5 shows the appropiate bits in each ESFR that need to be set to enable different functions for
each GPIO pin.
As Table 6-5 shows, some GPIOx pins can be configured for multiple alternate functionalities and
therefore the device implements a priority level for each GPIO configuration. The priority level is as
follows:
1. I2C
2. Input Capture / Output Compare
3. General Purpose I/Os
This means that if the IC1_ACT bit is set to 1 (enabling Input Capture 1 functionality on GPIO_1 pin) and
the DI_CTRL[1:0] bits are set to 0x01 (enabling I2C functionality on GPIO_1) then the GPIO_1 pin is
configured as I2C pin.
6.21.2 GPIO Buffers
The device includes five general purpose digital input/output buffers, one for each of the GPIO_x pin. The
buffers can be configured to operate as standard 8051W I/O buffers or other alternate functions such as
I2C and input capture/output compare. The direction of the buffers are controlled digitally depending on
the mode of the GPIO_x pin.
The device also offers a strong drive mode which allows the user to override the digital control signals
generated by the 8051W GPIO interface. This mode is set for a given IO buffer via the GPIO Strong
Output Drive Mode ESFR. When a ‘1’ is written to the ST_GPOx bit, a switch at the output of the Output
buffer is always closed, providing a means to strongly pull up or down the voltage on the GPIO_x pin
regardless of whether output data is low or high. It is important to note that the GPIO Strong Output Drive
Mode ESFR can be set independent of the function assigned to the GPIO buffers. Strong drive mode
should be disabled if the buffer should operate as an input or in I2C mode.
6.22 8051W UART
The TxD and RxD pins are connected to the 8051W UART. These pins can either be used for software
debugging or for implementing application-specific protocols. Both the TxD and RxD pins have their
respective unidirectional buffers.
6.23 DAC Output
The device includes two 12-bit digital to analog converters that produce a ratiometric output voltage with
respect to the VDD supply. The digital input comes from the DAC 1 or DAC 2 registers, where the 4 MSBs
reside in a separate address from the 8 LSBs. In order to update the analog outputs on the VOUTx
pins in a coherent manner, the software must update the MSBs first, followed by the LSBs.
34
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NOTE
Changes in the VDD voltage result in a proportional change in the output voltage because
the current reference for the DAC is derived from VDD.
6.24 Input Capture and Output Compare
The device has two Input Capture and two Output Compare ports. Table 6-5 shows the GPIO pins of the
device that can be used for Input Capture and Output Compare ports. The capture and compare
functionality uses a 16-bit Free Running Timer for the events.
6.24.1 Free Running Timer
The Free Running Timer is a 16-bit timer that is different from the 8051W native timers. The resolution of
the Free Running Timer can be set to either 1µs/bit or 0.5µs/bit using 10_20_MHZ bit in Input
Capture/Output Compare Control Register (IC_OC_CTRL) in the ESFR memory spacer.
The current value of the Free Running Timer can be accessed using the Free Running Timer Shadow
Registers (FRTMSB & FRTLSB). This register in only updated upon request, it is not continuously
updated. When the IC_OC_TIM_LAT bit in the Input Capture/Output Compare Control Register
(IC_OC_CTRL) is set to logic 1, the current value of the Free Running Timer is written to the Free
Running Timer Shadow registers.
6.24.2 Input Capture
The device has 2 Input Capture ports. The Input Capture functionality can be enabled when the pin is
configured to be a GPIO by setting ICx_ACT (x = 1,2) bits in the Input Capture/Output Compare GPIO
Register (IC_OC_GPIO) in the ESFR memory space. When the user sets the corresponding bit to logic
high, the GPIO pin is configured for Input Capture functionality automatically.
The Input Capture port can be configured to either capture the Free Running Timer value on a rising edge
or falling edge using the ICx_EDGE bits in the Input Capture/Output Compare Control Register
(IC_OC_CTRL) in the ESFR memory space. Both IC_1 and IC_2 each have unique 16-bit timer capture
registers associated with them called Input Capture 1 Register and Input Capture 2 Register respectively.
When the corresponding rising or falling edge occurs the Input Capture peripheral transfers the value of
the Free Running Timer into the corresponding capture register and generates an interrupt to the 8051W.
6.24.3 Output Compare
The device has 2 Output Compare ports. The Output Compare functionality can be enabled when the pin
is configured to be a GPIO by setting OCx_ACT (x = 1,2) bits in the Input Capture/Output Compare GPIO
Register (IC_OC_GPIO) in the ESFR memory space.
The Output Compare port can be configured to either (1) Set the pin to High level when the match occurs
or (2) Set the pin to Low level when the match occurs. The user can configure the desired state of the
OC_1 and OC_2 pins at match using OC1_LVL and OC2_LVL bits in the Input Capture/Output Compare
Control Register (IC_OC_CTRL) .
Each Output Compare port has a unique 16-bit timer compare register associated with it. When the value
programmed in the compare register matches the value of the Free Running Timer, the Output Compare
peripheral changes the state of the corresponding pin to the configured value and generates a unique
interrupt to the 8051W. This occurs every time the value in the Compare register matches the value of the
Free Running Timer.
NOTE
For correct function of the output compare it is recommended that the MSB be updated first
and then the LSB.
FUNCTIONAL DESCRIPTIONS
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6.25 Diagnostics
This section describes the diagnostics.
6.25.1 Power Supply Diagnostics
The device includes modules to monitor the power supply for faults. The internal power rails that are
monitored are AVDD, DVDD, VBRG, and EEPROM charge pump. Please refer to the electrical
specifications for the thresholds.
When a fault is detected, an appropriate bit in the PSMON1 and PSMON2 registers is set. If the faulty
condition is removed, the fault bits will remain latched. To remove the fault the 8051W software should
read the fault bit and write a logic zero back to the bit. In addition a system reset will clear the fault.
6.25.2 Resistive Bridge Sensor Connectivity Diagnostics
The device includes modules to monitor for sensor faults. Specifically, the device monitors the sensor pins
for opens (including loss of connection from the sensor), short-to-ground, and short to sensor supply.
When a fault is detected, an appropriate bit in the AFEDIAG register is set. All three types of sensor faults
will result in the setting of the same bit, meaning it is not possible to distinguish the type of fault that has
occured. Even after the faulty condition is removed, the fault bits remains latched. To remove the fault the
8051W software should read the fault bit and write a logic zero back to the bit. In addition a system reset
will clear the fault.
Open Sensor Faults are detected through the use of an internal pull-down resistor. The value of the
resistor can be configured using DIS_R1M and DIS_R2M bits in Decimator and Low Power Control
Register (DECCTRL) in the ESFR memory space. This configurability allows the detection of open sensor
faults for various Stage 1 Gain settings. For more information on programming this device please refer to
thePGA400-Q1 Programming Application Note (SLDA015).
6.25.3 AFE Diagnostics
The device includes modules that verify that the input signal of each stage is within a certain range. This
ensures that every stage of the signal chain is working normally. Overvoltage and undervoltage range
flags are implemented in four locations along the signal chain (Sensor Input, Stage 1 Gain output, Stage 2
Gain output, and ADC Buffer output). When a fault is detected, the corresponding bit is set in the
AFEDIAG registers. It is noted both overvoltage and undervoltage conditions set a common bit; i.e., it is
not possible to distinguish between overvoltage and undervoltage.
The AFE Diagnostics also includes the monitoring of the frequency of the Self-Oscillating Demodulator
circuit used for capacitive sensor interface. If the frequency is less than 40KHz (typical) or more than
1MHz (typical), a fault flag is set in the AFEDIAG register. The monitoring of this frequency can be
enabled or disabled using the CTOV_CLK_MON_EN bit in the ENABLE CONTROL register. Both overfrequency and under-frequency conditions set same bit which means it is not possible to distinguish which
type of fault occured that resulting in the flag.
The typical threshold values for these faults are in boxes in Figure 6-12.
When a fault is detected, an appropriate bit in the AFEDIAG register is set. All sensor faults will result in
the setting of the same bit, meaning there is no way to distinguish the type of fault. Even after the faulty
condition is removed, the fault bits will remain latched. To remove the fault the 8051W software should
read the fault bit and write a logic zero back to the bit. In addition a system reset will clear the fault.
36
FUNCTIONAL DESCRIPTIONS
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Figure 6-12. Block Diagram of AFE Diagnostics
6.25.4 Internal Capacitors for Capacitive Sensor Diagnostics
The device includes Cp and Cr Test capacitors that can be connected to the capacitive AFE via software
control. This allows the software to check the integrity of the capacitive signal chain in the IC.
Figure Figure 6-13 shows the block diagram with the Cp and Cr Test capacitors. The Cp Test capacitor is
10pF and Cr Test capacitor is 8pF.
PGA400
INT_CAPS_EN Bit in EN_CTRL ESFR
Input
Sensor
Select
CP1
CR1
From
Sensor
+
CPT
CRT
CP2
CR2
10pF
-
Capacitive
AFE
ADC
8051W
8pF
ICAP in CAPSEN ESFR
Figure 6-13. Internal Capacitors for Capacitive Sensor Diagnostics.
6.25.5 DAC Diagnostics
The device implements a “Loop Back” feature to check the integrity of the two DAC outputs. Figure
Figure 6-14 shows the block diagram representation of the Loop Back feature. This figure shows that
DAC1 output is connected to positive side of the differential input while DAC2 is connected to negative
side of the differential input.
The DAC outputs are voltage divided by a nominal factor of 6/11 before being connected to the AFE
inputs.
FUNCTIONAL DESCRIPTIONS
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PGA400
LB_EN Bit in EN_CTRL ESFR
Loop
Back
Input
Sensor
Select
VIN1P
VIN1R
From
Sensor
VIN2P
VIN2R
6/11
DAC1
DAC2
+
DAC1
Resistive
AFE
-
ADC
VOUT1
To ECU
8051W
DAC2
VOUT2
Figure 6-14. DAC Loop Back.
DAC loop back is enabled by setting LB_EN bit in EN_CTRL to 1. In this mode, Sensor 1 Channel gain
and offset settings are used. Note that ADC output represents the voltage difference between DAC1 and
DAC2 outputs scaled by the voltage divider and the AFE gains/offsets.
Note that when LB_EN is set to 1, the AFE is switched to resistive mode, even if SEN_TYP bit is set to
Capacitive mode.
The DAC outputs continue to be available on VOUT1 and VOUT2 pins in the Loop Back mode.
6.25.6 EEPROM CRC and TRIM Error
The 9th Byte in Bank 5 of the EEPROM stores the CRC for all the data in EEPROM Banks 1 through 5.
The user can verify the EEPROM CRC at any time by loading Banks 1 through 5 in sequence into the
EEPROM Cache. When Bank 5 is loaded into the Cache, the device automatically calculates the CRC
and updates the CRC_ERR bit in EE_STATUS ESFR.
The device also has analog trim values. The validity of the analog trim values is checked on power up and
before the 8051W reset is de-asserted. The validity of the trim values can be inferred using the
TRIM_ERR bit in EE_STATUS ESFR.
Note that Banks 0 can be updated by software in the field, but the user has to maintain CRC (or
checksum) for this bank using software.
6.25.7 RAM MBIST
The device implements RAM MBIST (Memory Built-In Self-Test). This diagnostic checks the integrity of
the internal RAM on an on-demand basis.
The procedure to start this diagnostic and check for status is as below:
• 1. Set EN_IRAM_MBIST to 1 in EN_CTRL2 register. This starts the RAM MBIST.
• 2. Wait for IRAM_MBIST_DONE in RAM_MBIST_ST to be set to 1 by the RAM MBIST algorithm
• 3. Check IRAM_MBIST_FAIL bit in RAM_MBIST_ST register after IRAM_MBIST_DONE flag is set to
1. If IRAM_MIBIST_FAIL is 1, then RAM MBIST failed, indicating faulty RAM. If IRAM_MBIST_FAIL is
0, then RAM has no faults.
The RAM MBIST can be run only once every power cycle.
NOTE
While the RAM MBIST is running, the 8051W should not access the RAM.
38
FUNCTIONAL DESCRIPTIONS
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6.25.8 Main Oscillator Watchdog
There is watch dog monitor for the main oscillator clock whether using the internal 40MHz oscillator or the
external crystal input. When the frequency is outside the range of 35-45MHz the entire device is reset.
The main oscillator watchdog can be disabled using MAIN_OSC_WD_EN bit in the ENABLE CONTROL
register.
6.25.9 Software Watchdog
The device also implements a software watchdog. This watchdog has to be serviced by software every
500ms. If the software does not service the watchdog within 500ms of the last service, then the 8051W
core is reset. The software services the watchdog by toggling the state of an internal pin between the two
blocks. The state of this pin cannot be read back to the 8051W. If this function is not desired the software
watchdog can be disabled using CPU_WD_EN bit in the ENABLE CONTROL register.
When the software watchdog times out and resets the 8051W, DAC1 and DAC2 registers are reset to 0,
which causes VOUT1 and VOUT2 to be driven to 0V. The remaining ESFRs retains the settings from prior
to the reset events. This implies that CPU_WD_EN also remains set.
6.26 Low Power Mode
The device has multiple low power modes. In each mode, certain functional blocks can be turned on or off
through the use of different ESFRs. Table 6-6 lists which bits in each ESFR that disables certain blocks of
the device.
Table 6-6. Low Power Control
CONTROL BIT
ESFR
CONTROL ACTION
VBRG_EN
SENCTRL
Enables/Disables VBRG supply
DAC2_EN
DECCTRL
Enables/Disables DAC2
AFE_EN
DECCTRL
Enables/Disable AFE
EN_DI_IF_CLK
EN_CTRL2
Enable/Disable Digital Interface
EN_EEPROM_CTRL_CLK
EN_CTRL2
Enable/Disable EEPROM clock
The following blocks does not enter low power mode at any time:
• Microprocessor – the microprocessor continues to operate at the same frequency
• OTP/EEPROM – The memory is kept alive and runs at the same speed VOUT1/OWI
FUNCTIONAL DESCRIPTIONS
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7 Application Schematic
7.1
Resistive Bridge Interface
7.2
Capacitive Sensor Interface
40
Application Schematic
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PACKAGE OPTION ADDENDUM
www.ti.com
6-Apr-2012
PACKAGING INFORMATION
Orderable Device
PGA400QYZSRQ1
Status
(1)
ACTIVE
Package Type Package
Drawing
DSBGA
YZS
Pins
Package Qty
36
1500
Eco Plan
(2)
Green (RoHS
& no Sb/Br)
Lead/
Ball Finish
SNAGCU
MSL Peak Temp
(3)
Samples
(Requires Login)
Level-1-260C-UNLIM
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
4-Apr-2012
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
PGA400QYZSRQ1
Package Package Pins
Type Drawing
SPQ
DSBGA
1500
YZS
36
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
180.0
12.4
Pack Materials-Page 1
3.79
B0
(mm)
K0
(mm)
P1
(mm)
3.79
0.71
8.0
W
Pin1
(mm) Quadrant
12.0
Q1
PACKAGE MATERIALS INFORMATION
www.ti.com
4-Apr-2012
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
PGA400QYZSRQ1
DSBGA
YZS
36
1500
210.0
185.0
35.0
Pack Materials-Page 2
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