ZLDO1117_10 DIODES [Diodes Incorporated], ZLDO1117_10 Datasheet - Page 7

• Manufacturer Part Number: ZLDO1117_10
• Description: 1A LOW DROPOUT POSITIVE REGULATOR 1.2V, 1.5V
• Manufacturer: DIODES [Diodes Incorporated]

A Product Line of
Diodes Incorporated
ZLDO1117
The device will require an output capacitor of 22µF tantalum or 150µF aluminum electrolytic when the adjust pin is bypassed.
Normally, capacitor values on the order of 100µF are used in the output of many regulators to ensure good load transient
response with large load current changes. Output capacitance can be increased without limit and larger values of output
capacitance further improve stability and transient response.
The curves for Ripple Rejection were generated using an adjustable device with the adjust pin bypassed. These curves will
hold true for all values of output voltage. For proper bypassing, and ripple rejection approaching the values shown, the
impedance of the adjust pin capacitor, at the ripple frequency, should be < R1. R1 is normally in the range of 100Ω to 200Ω.
The size of the required adjust pin capacitor is a function of the input ripple frequency. At 120Hz, with R1 = 100Ω, the adjust
pin capacitor should be >13µF. At 10kHz only 0.16µF is needed.
For fixed voltage devices, and adjustable devices without an adjust pin capacitor, the output ripple will increase as the ratio of
the output voltage to the reference voltage (V
/V
). For example, with the output voltage equal to 5V, the output ripple will
OUT
REF
be increased by the ratio of 5V/1.25V. It will increase by a factor of four. Ripple rejection will be degraded by 12dB from the
value shown on the curve.
ZLDO1117
7 of 12
July 2010
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© Diodes Incorporated
Document number: Ds32018 Rev. 4 - 2