ENVIRONMENTAL CONDITIONS |
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Ambient Temperature Rating: |
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TAMB | = TCASE – (PD x θCA) |
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TCASE | = Case Temperature in °C |
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PD | = Power Dissipation in W |
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θCA | = | Thermal Resistance |
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θJA | = | Thermal Resistance | ||||
θJC | = | Thermal Resistance |
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Package |
| uJA |
| uJC |
| uCA |
TQFP |
| 50°C/W |
| 2°C/W |
| 48°C/W |
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POWER DISSIPATION
To determine total power dissipation in a specific application, the following equation should be applied for each output:
C× VDD2 × f
C = load capacitance, f = output switching frequency.
Example
In an application where external data memory is used and no other outputs are active, power dissipation is calculated as follows:
Assumptions
•External data memory is accessed every cycle with 50% of the address pins switching.
•External data memory writes occur every other cycle with 50% of the data pins switching.
•Each address and data pin has a 10 pF total load at the pin.
•The application operates at VDD = 5.0 V and tCK = 30 ns.
Total Power Dissipation = PINT + (C × VDD2 × f)
PINT = internal power dissipation from Power vs. Frequency graph (Figure 8).
(C × VDD2 × f) is calculated for each output:
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| 3 VDD2 |
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| Pins | 3 C | 3f |
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Address, DMS | 8 | × 10 pF | × 52 | V | × 33.3 MHz = | 66.6 mW |
Data Output, WR | 9 | × 10 pF | × 52 | V | × 16.67 MHz = 37.5 mW | |
RD | 1 | × 10 pF | × 52 | V | × 16.67 MHz = | 4.2 mW |
CLKOUT | 1 | × 10 pF | × 52 | V | × 33.3 MHz = | 8.3 mW |
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| 116.6 mW | |
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Total power dissipation for this example is PINT + 116.6 mW.
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| 450 | 2186 POWER, INTERNAL1, 3, 4, 5 | ||
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| 425 |
| VDD = 5.5V | |
| 400 |
| 430mW | |
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| 370mW | ||
– mW | 375 |
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350 | 330mW | 325mW | ||
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INT | 325 |
| VDD = 5.0V | |
(P | 300 |
| 275mW | |
POWER |
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275 | 245mW |
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250 | 235mW | |||
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| 225 |
| VDD = 4.5V | |
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| 195mW | ||
| 200 | 175mW |
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| 175 |
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| 150 |
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| 30 | 32 | 34 | 36 | 38 | 40 | 42 |
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| 1/fCK – MHz |
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| 85 |
| POWER, IDLE1, 2, 3, 5 |
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| 84mW | |
| 80 |
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| 76mW |
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| 75 | 69mW |
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| VDD = 5.5V |
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– mW | 70 |
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| 67mW | ||
65 |
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| 61mW |
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) |
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IDLE | 60 | 56mW |
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| VDD = 5.0V |
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(P | 55 |
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| 54mW |
POWER |
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| 49mW |
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50 |
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45mW |
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45 |
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| 40 |
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| 35 |
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| 30 | 32 | 34 | 36 | 38 | 40 | 42 |
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| 1/fCK – MHz |
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| 70 |
| POWER, IDLE n MODES3, 5 |
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| 67mW | IDLE | |
| 65 |
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| 61mW |
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mW | 60 |
| 56mW |
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55 |
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n) – | 50 |
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IDLE |
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(P | 45 |
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POWER | 35 |
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| 32mW |
| 34mW | IDLE (16) |
| 40 |
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| 30 |
| 30mW |
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| 32mW | IDLE (128) |
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| 30mW |
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| 25 |
| 28mW |
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| 20 | 30 | 32 | 34 | 36 | 38 | 40 | 42 |
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| 1/fCK – MHz |
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VALID FOR ALL TEMPERATURE GRADES.
1POWER REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.
2IDLE REFERS TO
3TYPICAL POWER DISSIPATION AT 5.0V VDD AND TA = 25°C EXCEPT WHERE SPECIFIED.
4IDD MEASUREMENT TAKEN WITH ALL INSTRUCTIONS EXECUTING FROM INTERNAL MEMORY. 50% OF THE INSTRUCTIONS ARE MULTIFUNCTION (TYPES 1, 4, 5, 12, 13, 14 30% ARE TYPE 2 AND TYPE 6, AND 20% ARE IDLE INSTRUCTIONS.
5SPECIFICATIONS AT 40MHz ARE PRELIMINARY AT THIS PRINTING.
Figure 8. Power vs. Frequency
REV. 0 |