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| 型号： | EM78459 |
| 英文描述： | Dual Advanced Synchronous Rectified Buck MOSFET Drivers with Pre-POR OVP; Temperature Range: -40°C to 85°C; Package: 14-SOIC |
| 中文描述： | 8位微控制器的通用产品 |
| 文件页数： | 43/57页 |
| 文件大小： | 854K |
| 代理商： | EM78459 |
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EM78458/459
MASK ROM
This specification is subject to change without prior notice.
2002/03/01
48
4.13 Power-on Considerations
Any microcontroller is not warranted to start proper operation before the power supply stabilizes in
steady state.
EM78458/459 is equipped with Power On Voltage Detector (POVD) with detection level range of 1.4
V to 2.0 V. The circuitry eliminates the extra external reset circuit. It will work well if Vdd rises quickly
enough (50 ms or less). However, under critical applications, extra devices are still required to assist
in solving power on problems.
1. External Power on Reset Circuit
The circuit shown in Fig IV.13.1-1 implements an external RC to produce a reset pulse. The pulse
width (time constant) should be kept long enough to allow Vdd to reach minimum operation voltage.
This circuit is used when the power supply has a slow rise time. Because the current leakage from the
/RESET pin is about
±5A, it is recommended that R should not be great than 40 K. In this way, the
voltage at Pin /RESET is held below 0.2V. The diode (D) acts as a short circuit at power-down. The
capacitor, C, is discharged rapidly and fully. Rin, the current-limited resistor, prevents high current
discharge or ESD (electrostatic discharge) from flowing into Pin /RESET.
EM78458
EM78459
/RESET
VDD
D
R
Rin
C
Fig. 24 External Power on Reset Circuit
2. Residue-Voltage Protection
When battery is replaced, device power (Vdd) is taken off but residue-voltage remains. The
residue-voltage may trips below Vdd minimum, but not to zero. This condition may cause a poor
power on reset. Fig. 25 and Fig. 26 show how to build a residue-voltage protection circuit
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相关代理商/技术参数 |
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|---|---|
| EM78459AK | 制造商:EMC 制造商全称:ELAN Microelectronics Corp 功能描述:8-Bit Microcontroller with MASK ROM |
| EM78459AM | 制造商:EMC 制造商全称:ELAN Microelectronics Corp 功能描述:8-Bit Microcontroller with MASK ROM |
| EM78468 | 制造商:EMC 制造商全称:ELAN Microelectronics Corp 功能描述:8-BIT Microcontroller |
| EM78468AQ | 制造商:EMC 制造商全称:ELAN Microelectronics Corp 功能描述:8-BIT Microcontroller |
| EM78468BQ | 制造商:EMC 制造商全称:ELAN Microelectronics Corp 功能描述:8-BIT Microcontroller |
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