ZHCSH72I September   2011  – December 2017

PRODUCTION DATA.

1. 特性
2. 应用
3. 说明
1.     Device Images
4. 修订历史记录
5. Device Comparison Table
6. Pin Configuration and Functions
7. Specifications
8. Parameter Measurement Information
9. Detailed Description
1. 9.1 Overview
2. 9.2 Functional Block Diagram
3. 9.3 Feature Description
1. 9.3.1 VCC and VCCO Power Supplies
2. 9.3.2 Clock Inputs
3. 9.3.3 Clock Outputs
10. 10Application and Implementation
11. 11Power Supply Recommendations
12. 12器件和文档支持
1. 12.1 文档支持
2. 12.2 社区资源
3. 12.3 商标
4. 12.4 静电放电警告
5. 12.5 Glossary
13. 13机械、封装和可订购信息

• RHS|48
• RHS|48

#### 11.2.2 Power Dissipation Example #2: Worst-Case Dissipation

This example shows how to calculate IC power dissipation for a configuration to estimate worst-case power dissipation. In this case, the maximum supply voltage and supply current values specified in Electrical Characteristics are used.

• Max VCC = VCCO = 3.465 V. Max ICC and ICCO values.
• CLKin0/CLKin0* input is selected.
• Banks A and B are configured for LVPECL: all outputs terminated with 50 Ω to VT = Vcco - 2 V.
• REFout is enabled with 5 pF load.
• TA = 85 °C

Using the maximum supply current and power calculations from the previous section, we can compute PTOTAL and PDEVICE.

• From Equation 5: ICC_TOTAL = 10.5 mA + 27 mA + 27 mA + 5.5 mA = 70 mA
• From ICCO_PECL max spec: ICCO_BANK_A = ICCO_BANK_B = 197 mA
• From Equation 7: PTOTAL = 3.465 V * (70 mA + 197 mA + 197 mA + 10 mA) = 1642.4 mW
• From Equation 8: PRT_PECL = ((2.57 V - 1.47 V)2/50 Ω) + ((1.72 V - 1.47 V)2/50 Ω) = 25.5 mW (per output pair)
• From Equation 9: PVTT_PECL = 1.47 V * [ ((2.57 V - 1.47 V) / 50 Ω) + ((1.72 V - 1.47 V) / 50 Ω) ] = 39.5 mW (per output pair)
• From Equation 10: PRT_HCSL = 0 mW (no HCSL outputs)
• From Equation 11: PDEVICE = 1642.4 mW - (10 * (25.5 mW + 39.5 mW)) - 0 mW = 992.4 mW

In this worst-case example, the IC device will dissipate about 992.4 mW or 60% of the total power (1642.4 mW), while the remaining 40% will be dissipated in the LVPECL emitter resistors (255 mW for 10 pairs) and termination voltage (395 mW into Vcco - 2 V).

Based on θJA of 28.5 °C/W, the estimated die junction temperature would be about 28.3 °C above ambient, or 113.3 °C when TA = 85 °C.