AMS 1117

7.00

1A LOW DROPOUT VOLTAGE REGULATOR

The AMS1117 series of adjustable and fixed voltage regulators are designed to provide up to1A output current and to operate down to 1V input-to-output differential. The dropout voltage of the device is guaranteed maximum 1.3V, decreasing at lower load currents. On-chip trimming adjusts the reference voltage to 1.5%. Current limit is set to minimize the stress under overload conditions on both the regulator and power source circuitry. The AMS1117 devices are pin compatible with other three-terminal SCSI regulators and are offered in the low profile surface mount SOT-223 package, in the 8L SOIC package and in the TO-252 (DPAK) plastic package.

FEATURES

  • Three Terminal Adjustable or Fixed Voltages
    1.5V, 1.8V, 2.5V, 2.85V, 3.3V and 5.0V
  • Output Current of 1A
  • Operates Down to 1V Dropout
  • Line Regulation: 0.2% Max.
  • Load Regulation: 0.4% Max.
  • SOT-223, TO-252 and SO-8 package available

APPLICATIONS

  • High Efficiency Linear Regulators
  • Post Regulators for Switching Supplies
  • 5V to 3.3V Linear Regulator
  • Battery Chargers
  • Active SCSI Terminators
  • Power Management for Notebook
  • Battery Powered Instrumentation

Stability

The circuit design used in the AMS1117 series requires the use of an output capacitor as part of the device frequency compensation. The addition of 22µF solid tantalum on the output will ensure stability for all operating conditions. When the adjustment terminal is bypassed with a capacitor to improve the ripple rejection, the requirement for an output capacitor increases. The value of 22µF tantalum covers all cases of bypassing the adjustment terminal. Without bypassing the adjustment terminal smaller capacitors can be used with equally good results. To further improve stability and transient response of these devices larger values of output capacitor can be used.

Protection Diodes

Unlike older regulators, the AMS1117 family does not need any protection diodes between the adjustment pin and the output and from the output to the input to prevent over-stressing the die. Internal resistors are limiting the internal current paths on the AMS1117 adjustment pin, therefore even with capacitors on the adjustment pin no protection diode is needed to ensure device safety under short-circuit conditions.

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