Datasheet MAX8863, MAX8864 (Analog Devices) - 8

link to page 3 link to page 3 link to page 3 link to page 3 link to page 3 MAX8863T/S/R, Low-Dropout, 120mA Linear Regulators MAX8864T/S/R
Operating Region and Power Dissipation
located several inches from the power source. Improve Maximum power dissipation of the MAX8863/MAX8864 load-transient response, stability, and power-supply rejection depends on the thermal resistance of the case and circuit by using large output capacitors. For stable operation board, the temperature difference between the die junction over the full temperature range, with load currents up to and ambient air, and the rate of air flow. The power 120mA, a minimum of 1μF is recommended. dissipation across the device is P = IOUT (VIN - VOUT).
Noise
The resulting maximum power dissipation is: The MAX8863/MAX8864 exhibit 350μVRMS noise during PMAX = (TJ - TA) / θJA normal operation. When using the MAX8863/MAX8864 where (TJ - TA) is the temperature difference between the in applications that include analog-to-digital converters MAX8863/MAX8864 die junction and the surrounding air, of greater than 12 bits, consider the ADC’s power-supply and θJA is the thermal resistance of the chosen package rejection specifications (see the Output Noise DC to to the surrounding air. 1MHz photo in the Typical Operating Characteristics). The GND pin of the MAX8863/MAX8864 performs the
Power-Supply Rejection and Operation
dual function of providing an electrical connection to
from Sources Other than Batteries
ground and channeling heat away. Connect the GND pin The MAX8863/MAX8864 are designed to deliver low to ground using a large pad or ground plane. dropout voltages and low quiescent currents in battery-
Reverse Battery Protection
powered systems. Power-supply rejection is 62dB at low The MAX8863/MAX8864 have a unique protection frequencies and rolls off above 300Hz. As the frequency scheme that limits the reverse supply current to less than increases above 20kHz, the output capacitor is the major 1mA when either V contributor to the rejection of power-supply noise (see IN or VSHDN falls below ground. The circuitry monitors the polarity of these two pins, the Power-Supply Rejection Ratio vs. Ripple Frequency disconnecting the internal circuitry and parasitic diodes graph in the Typical Operating Characteristics). when the battery is reversed. This feature prevents the When operating from sources other than batteries, device from overheating and damaging the battery. improve supply-noise rejection and transient response by increasing the values of the input and output capacitors,
VIN > 5.5V Minimum Load Current
and using passive filtering techniques (see the supply When operating the MAX8863/MAX8864 with an input and load-transient responses in the Typical Operating voltage above 5.5V, a minimum load current of 20μA is Characteristics). required to maintain regulation in preset voltage mode. When setting the output with external resistors, the
Load Transient Considerations
minimum current through the external feedback resistors The MAX8863/MAX8864 load-transient response and load must be 30μA. graphs (see Typical Operating Characteristics) show two components of the output response: a DC shift of the
Applications Information
output voltage due to the different load currents, and the
Capacitor Selection and Regulator Stability
transient response. Typical overshoot for step changes in the load current from 0mA to 50mA is 12mV. Increasing Normally, use a 1μF capacitor on the input and a 1μF the output capacitor’s value and decreasing its ESR capacitor on the output of the MAX8863/MAX8864. attenuates transient spikes. Larger input capacitor values and lower ESR provide better supply-noise rejection and transient response. A higher-value input capacitor (10μF) may be necessary if large, fast transients are anticipated and the device is www.maximintegrated.com Maxim Integrated │

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