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H1117 Datasheet(PDF) 4 Page - Hi-Sincerity Mocroelectronics |
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H1117 Datasheet(HTML) 4 Page - Hi-Sincerity Mocroelectronics |
4 / 8 page HI-SINCERITY MICROELECTRONICS CORP. Spec. No. : IC200401 Issued Date : 2004.02.01 Revised Date : 2005.07.14 Page No. : 4/8 H1117 Series HSMC Product Specification Applications Description • Output Voltage Adjustment Like most regulators, H1117 series regulate the output by comparing the output voltage to an internally generated reference voltage. On the adjustable version, the V REF is available externally as 1.25V between V OUT and ADJ. The voltage ratio formed by R1 and R 2 should be set to conduct 10mA (minimum output load). The output voltage is given by the following equation: V OUT =VREF (1+R 2/R1) + IADJ R2 On fixed versions of H1117 series, the voltage divider is provided internally. • Thermal Protection H1117 series have thermal protection which limits junction temperature to 150 °C. However, device functionality is only guaranteed to a maximum junction temperature of +125 °C. The power dissipation and junction temperature for H1117 in all packages given by P D=(VIN - VOUT) IOUT, TJUNCTION=TAMBIENT+(PDxθJA), Note: TJUNCTION must not exceed 125°C • Current Limit Protection H1117 series are protected against overload conditions. Current protection is triggered at typically 1.5A. • Stability And Load Regulation H1117 series require a capacitor from V OUT to GND to provide compensation feedback to the internal gain stage. This is to ensure stability at the output terminal. Typically, a 10uF tantalum or 50uF aluminum electrolytic is sufficient. Note : It is important that the ESR for this capacitor does not exceed 0.5 Ω. The output capacitor does not have a theoretical upper limit and increasing its value will increase stability. C OUT = 100 uF or more is typical for high current regulator design. H1117 series load regulation are limited by the resistance of the wire connecting it to the load(R P). For the adjustable version, the best load regulation is accomplished when the top of the resistor divider(R 1) is connected directly to the output pin of the H1117 series. When so connected, R P is not multiplied by the divider ratio. For fixed output versions, the top of R 1 is internally connected to the output and ground pin can be connected to low side of the load as a negative side sense if, so desired. • Thermal Consideration The H1117 series contain thermal limiting circuitry designed to protect itself for over-temperature conditions. Even for normal load conditions, maximum junction temperature ratings must not be exceeded. As mention in thermal protection section, we need to consider all sources of thermal resistance between junction and ambient. It contains junction-to-case, case-to- heat-sink interface and heat sink resistance itself. An additional heat sink is applied externally sometimes. It can increase the maximum power dissipation. For example, the equivalent junction temperature of 300mA output current is 115 °C without external heat sink. Under the same junction temperature IC can operates 500mA with an adequate heat sink. Therefore, to attach an extra heat sink is recommended. Junction-to-case thermal resistance is specified from the IC junction to the bottom of the case directly below the die. The bonding wires are appending paths. The former is the lowest resistance path. Proper mounting is required to ensure the best possible thermal flow this area of the package to the heat sink. Thermal compound at the case-to-heat-sink interface is strongly recommended. The case of all devices in this series is electrically connected to the output. Therefore, if the case of the device must be electrically isolated, a thermally conductive spacer can be used, as long its thermal resistance is considered. • Protection Diode (The figure is shown as Regulator with Reverse Diode Protection in advanced applications) In general operation, H1117 series don’t need any protection diodes. From the cross-section structure of H1117 sries, the output pin is connected to P+ substrate, and the input pin is connected to N- well. There is a parasitic reverse diode between them. It can handle microsecond surge currents of 5A to 10A. Even with large output capacitance, it is very difficult to get those values of surge currents in normal operation. Only with high value output capacitors, such as 1000uF. And with the input pin instantaneously shorted to ground. can damage occur. A crowbar circuit at the input of the H1117 series can generate those kinds of currents, and a diode from output to input is recommended. Normal power supply cycling or even plugging and unplugging in the system will not generate currents large enough to do any damage. RL R1 R2 Connect R1 to Case Connect R2 to Load Out In Adj R P Parasitic Line Resistance V IN V OUT =VREF (1+R2/R1) + IADJ R2 VIN R1 R2 V REF In Out ADJ IADJ 10uA VOUT |
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