Datasheet LT3013B (Analog Devices) - 10
| 制造商 | Analog Devices |
| 描述 | 250mA, 4V to 80V Low Dropout Micropower Linear Regulator with PWRGD |
| 页数 / 页 | 16 / 10 — APPLICATIONS INFORMATION. Figure 4. PWRGD Circuit Block Diagram. Thermal … |
| 文件格式/大小 | PDF / 178 Kb |
| 文件语言 | 英语 |
APPLICATIONS INFORMATION. Figure 4. PWRGD Circuit Block Diagram. Thermal Considerations
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LT3013B
APPLICATIONS INFORMATION
ICT 3μA CT PWRGD ADJ + V J Q CT(HIGH) – VBE (~1.1V) K VREF • 90% – – + VCT(LOW) ~0.1V 3013 F04
Figure 4. PWRGD Circuit Block Diagram
timing capacitor. Once the voltage on the CT pin reaches not apply for all possible combinations of input voltage the VCT(HIGH) threshold (approximately 1.7V at 25°C), the and output current. Operating the LT3013B beyond the capacitor voltage is clamped and the PWRGD pin is set to maximum junction temperature rating may impair the a high impedance state. life of the device. During normal operation, an internal glitch fi lter will ignore
Thermal Considerations
short transients (<15μs). Longer transients below the 90% threshold will reset the JK fl ip-fl op. This fl ip-fl op ensures The power handling capability of the device will be limited that the capacitor on the C by the maximum rated junction temperature (125°C). The T pin is quickly discharged all the way to the V power dissipated by the device will be made up of two CT(LOW) threshold before restarting the time delay. This provides a consistent time delay after the components: ADJ pin is within 10% of the regulated voltage before the 1. Output current multiplied by the input/output voltage PWRGD pin switches to high impedance. differential: IOUT • (VIN – VOUT) and,
Current Limit and Safe Operating Area Protection
2. GND pin current multiplied by the input voltage: I Like many IC power regulators, the LT3013B has safe op- GND • VIN. erating area protection. The safe operating area protection The GND pin current can be found by examining the GND decreases the current limit as the input voltage increases Pin Current curves in the Typical Performance Character- and keeps the power transistor in a safe operating region. istics. Power dissipation will be equal to the sum of the The protection is designed to provide some output current two components listed above. at all values of input voltage up to the device breakdown The LT3013B series regulators have internal thermal limiting (see curve of Current Limit vs Input Voltage in the Typical designed to protect the device during overload conditions. Performance Characteristics). For continuous normal conditions the maximum junction The LT3013B is limited for operating conditions by maxi- temperature rating of 125°C must not be exceeded. It is mum junction temperature. While operating at maximum important to give careful consideration to all sources of input voltage, the output current range must be limited; thermal resistance from junction to ambient. Additional when operating at maximum output current, the input heat sources mounted nearby must also be considered. voltage range must be limited. Device specifi cations will 3013bfb 10
APPLICATIONS INFORMATION
ICT 3μA CT PWRGD ADJ + V J Q CT(HIGH) – VBE (~1.1V) K VREF • 90% – – + VCT(LOW) ~0.1V 3013 F04
Figure 4. PWRGD Circuit Block Diagram
timing capacitor. Once the voltage on the CT pin reaches not apply for all possible combinations of input voltage the VCT(HIGH) threshold (approximately 1.7V at 25°C), the and output current. Operating the LT3013B beyond the capacitor voltage is clamped and the PWRGD pin is set to maximum junction temperature rating may impair the a high impedance state. life of the device. During normal operation, an internal glitch fi lter will ignore
Thermal Considerations
short transients (<15μs). Longer transients below the 90% threshold will reset the JK fl ip-fl op. This fl ip-fl op ensures The power handling capability of the device will be limited that the capacitor on the C by the maximum rated junction temperature (125°C). The T pin is quickly discharged all the way to the V power dissipated by the device will be made up of two CT(LOW) threshold before restarting the time delay. This provides a consistent time delay after the components: ADJ pin is within 10% of the regulated voltage before the 1. Output current multiplied by the input/output voltage PWRGD pin switches to high impedance. differential: IOUT • (VIN – VOUT) and,
Current Limit and Safe Operating Area Protection
2. GND pin current multiplied by the input voltage: I Like many IC power regulators, the LT3013B has safe op- GND • VIN. erating area protection. The safe operating area protection The GND pin current can be found by examining the GND decreases the current limit as the input voltage increases Pin Current curves in the Typical Performance Character- and keeps the power transistor in a safe operating region. istics. Power dissipation will be equal to the sum of the The protection is designed to provide some output current two components listed above. at all values of input voltage up to the device breakdown The LT3013B series regulators have internal thermal limiting (see curve of Current Limit vs Input Voltage in the Typical designed to protect the device during overload conditions. Performance Characteristics). For continuous normal conditions the maximum junction The LT3013B is limited for operating conditions by maxi- temperature rating of 125°C must not be exceeded. It is mum junction temperature. While operating at maximum important to give careful consideration to all sources of input voltage, the output current range must be limited; thermal resistance from junction to ambient. Additional when operating at maximum output current, the input heat sources mounted nearby must also be considered. voltage range must be limited. Device specifi cations will 3013bfb 10