Low drop positive adjustable or fixed mode voltage regulator

The AP1117 is a low-drop positive adjustable or fixed-mode voltage regulator with 1A output current capability. The product is specifically designed to provide well-regulated voltages for low IC applications such as high speed bus terminals and low current 3.3V logic power supplies. The regulator is also ideal for other applications such as VGA cards.

The AP1117 is guaranteed to have a sub-1.4V dropout at full load, enabling it to provide a well-tuned output of 1.25 to 5.0 at 6.4V to 18V input power. AP1117 is available in commercial temperature grades (AP1117) and industrial temperature ranges (AP1117I) (TO252 and SOT223).

Features

● 1.4V full load current Maximum drop current
● Fast transient response
● Output current limit
● "Built-in Hot Shutdown"
● Good noise suppression
● 3 terminals adjustable or fixed 1.5V, 1.8V, 2.5V, 3.3V, 5.0V
● Working junction temperature range
-    0°C≤TJ≤+125°C(All packs)
-   -20°C≤TJ≤+125°C(see ordering information)
-   -40°C≤TJ≤+125°C(see ordering information)
● Lead-free package :SOT223, TO252, SOT89-3, TO263 and TO220-3
● Completely lead-free; RoHS compliant
● SOT223, TO252, SOT89-3, TO263, TO220-3: Available in "Green" Forming Glue (no Br, Sb)
● Free of halogens and antimony. "Green" devices

Applications

● Computer peripheral
● Communication
● Consumer equipment

Application Information

Load Regulation

To improve load regulation, AP1117-ADJ should have an upper feedback resistor R1, connected to VOUT as close as possible, and a lower resistor R2, connected to load GND return as close as possible. This helps to reduce any parasitic drag in series with the load.

Stability and Decoupling Capacitors

Input capacitance

To ensure stable operation, the input power supply must be low impedance, up to several MHz in frequency. This requires a tightly placed input decoupling capacitor with a minimum of 4.7 μF. This can be either ceramic tantalum or solid tantalum. The ESR value of the capacitor must be less than 0.5Ω.

Output Capacitor

The AP1117 also requires a tightly placed output capacitor as part of the device frequency compensation. As part of its superior performance to the industry standard 1117, the AP1117 is suitable for MLCC(multilayer ceramic chip) capacitors. Minimum output capacitance of 4.7 μF ceramic X7R or 4.7 μF tantalum solid is required. Aluminum electrolysis can be used, but requires a minimum of 47 μF. When using aluminum electrolysis, it is still recommended to use 1 μF MLCC together. The ESR of the output capacitor must be less than 0.5Ω. AP1117 is stable when the correct MLCC capacitance value is used. When using MLCC capacitors, X7R dielectrics are recommended. Do not use Y5V dielectric.

Capacitor Track Length

Both input and output capacitors must be placed close to the AP1117. PCB traces not longer than 10mm are recommended  between the AP1117 and the capacitors.

Thermal Considerations

Thermal protection circuitry will shut down the regulator should the junction temperature exceed typically +150°C at the. Thermal protection circuitry will shut down the regulator should the junction temperature exceed typically +150°C at the junction sense point. The AP1117 is pin compatible with similar '1117 regulators and offers extended temperature range and. Sense point. The AP1117 is pin compatible with similar' 1117 regulators and offers extended temperature range and improved regulation specifications.

AP1117 series regulators have internal thermal limiting circuitry designed to  protect the device during overload conditions. For continuous normal  load conditions however,  the maximum junction temperature rating of +125°C must not be exceeded. It is important to give careful consideration to  all sources of thermal resistance from junction to ambient. For the SOT223 and TO252 packages,   which are designed to be surface mounted,  additional heat sources mounted near the device must also be considered. Heat sinking is  accomplished using the heat  spreading capability of the PCB and its copper traces.

The θJC (junction to tab) of the TO252 and SOT223 are +12°C/W and +15°C/W respectively. Thermal resistances from tab to ambient can be as low as 30°C/W. The total thermal resistance. +15°C/W respectively. Thermal resistances from TAB to ambient can be as low as 30°C/ w from junction to ambient (θJA) can be as low as +42 ~ +46°C/W. This requires a reasonable sized PCB with at least one layer of copper to spread the heat across the board and couple it into  the surrounding air.

Datasheet specifications  using 2 oz copper and a 5mm x 5mm pad with TA = +27°C, no air flow yielded θJA (junction to tab) of +73°C/W and +107°C/W for TO252 and SOT223 respectively. The thermal resistance for each application will be affected by thermal interactions with other components on the board. Some  experimentation  will be necessary to determine the actual value. See graphs of power dissipation and thermal pictures  of different size PCB copper area for  guidance.