537
Figure 8. TMS370 Based External Noise Suppression Circuitry
R2
R1
R3
C1
External Conditioning
Circuitry
Vehicle Battery (Vbat)
µ
C Input
VCCD
VCCD
IPIN
The system cost advantages of designing with the TMS370 family of microcontrollers becomes quite
evident when compared to competitive microcontrollers that do not contain internal diode protection
circuitry or TTL input levels.
Designing Input Protection Circuitry for TMS370 Microcontrollers
The next step in the cost reduction process is to design the input protection circuitry to meet the criteria
for transient suppression and the TTL input thresholds. This section provides an example for selecting the
two external resistors (R2 and R3) required for a simple voltage divider protection circuit.
Using the external current limiting resistor (R2), you can limit the voltage and current seen on the I/O pins
such that external protection diodes are not needed. There are two absolute maximum specifications that
must be considered. These are:
•
Input and output clamp current: This specification is equal to
$20 mA when V
IN
(or V
OUT
)
is less than V
SS2
or greater than V
CCD2
.
•
Input voltage range: This specification is equal to a minimum of – 0.6V or a maximum of 7V
on all pins except INT1. For INT1, the minimum is – 0.6 V and the maximum is 14 V.
Continuous power dissipation should also be considered when selecting the external circuitry. Continuous
power dissipation is dependent on package type and the maximum ambient temperature requirement. The
real requirement is that the maximum power consumption of the package not be violated during the
transient.
NOTE:
Remember that transient suppression is designed to protect the
microcontroller from overvoltage conditions and not for normal operation.
The TMS370 family has gone through several silicon shrinks. These are redesigns that use smaller silicon
geometries. The TMS370 has gone through two shrinks commonly referred to as the 80% silicon and the
*
Summary of Contents for TMS370 Series
Page 1: ...TMS370 Microcontroller Family Application Book 1996 8 Bit Microcontroller Family ...
Page 2: ...Printed in U S A February 1996 SPNA017 ...
Page 3: ...1996 Application TMS370 Microcontroller Family Book ...
Page 20: ...1 Part I Introduction ...
Page 21: ...2 ...
Page 22: ...3 Introduction Microcontroller Products Semiconductor Group Texas Instruments ...
Page 23: ...4 ...
Page 25: ...6 ...
Page 27: ...8 ...
Page 29: ...10 ...
Page 31: ...12 ...
Page 33: ...14 ...
Page 37: ...18 ...
Page 39: ...20 ...
Page 41: ...22 ...
Page 43: ...24 ...
Page 45: ...26 ...
Page 47: ...28 ...
Page 49: ...30 ...
Page 81: ...62 ...
Page 82: ...63 Clear RAM Microcontroller Products Semiconductor Group Texas Instruments ...
Page 83: ...64 ...
Page 85: ...66 ...
Page 86: ...67 RAM Self Test on the TMS370 Microcontroller Products Semiconductor Group Texas Instruments ...
Page 87: ...68 ...
Page 89: ...70 ...
Page 90: ...71 ROM Checksum on the TMS370 Microcontroller Products Semiconductor Group Texas Instruments ...
Page 91: ...72 ...
Page 95: ...76 ...
Page 97: ...78 ...
Page 98: ...79 Bubble Sort With the TMS370 Microcontroller Products Semiconductor Group Texas Instruments ...
Page 99: ...80 ...
Page 101: ...82 ...
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Page 313: ...294 ...
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Page 319: ...300 ...
Page 323: ...304 ...
Page 324: ...305 T1PWM Set Up Routines Microcontroller Products Semiconductor Group Texas Instruments ...
Page 325: ...306 ...
Page 327: ...308 ...
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Page 331: ...312 ...
Page 387: ...368 ...
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Page 393: ...374 ...
Page 395: ...376 ...
Page 396: ...377 PACT Command Macros Microcontroller Products Semiconductor Group Texas Instruments ...
Page 397: ...378 ...
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Page 491: ...472 ...
Page 492: ...473 Part V External Memory Expansion Examples ...
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