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MAX8902A Datasheet(PDF) 7 Page - Maxim Integrated Products |
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MAX8902A Datasheet(HTML) 7 Page - Maxim Integrated Products |
7 / 9 page The BYP capacitor value can be adjusted from 0.001µF to 0.1µF to change the startup slew rate according to the following formula: Startup slew rate = (5V / ms) x (0.01µF / CBYP) Note that this slew rate applies only at startup, and that recovery from a short circuit occurs at a slew rate approximately 500 times slower. Also note that, being a low-frequency filter node, BYP is sensitive to leakage. BYP leakage currents above 10nA cause measurable inaccuracy at the output and should be avoided. Protection Features The MAX8902A/MAX8902B are fully protected from an output short circuit by a current-limiting and thermal- overload circuit. If the output is shorted to GND, the output current is limited to 700mA (typ). Under these conditions, the part quickly heats up. When the junction temperature reaches +165°C, a thermal-limit circuit shuts off the output device. When the junction cools to +150°C, the output turns back on in an attempt to reestablish regulation. While the fault persists, the out- put current cycles on and off, as the junction tempera- ture slews between +150°C and +165°C. The MAX8902A/MAX8902B are also protected against reverse current when the output voltage is higher than the input. In the event that extra output capacitance is used at the output, a power-down transient at the input would normally cause a large reverse current through a conventional regulator. The MAX8902A/MAX8902B include a reverse voltage detector that trips when IN drops 10mV below OUT, shutting off the regulator and opening the pMOS body diode connection, preventing any reverse current. Thermal Considerations The MAX8902A/MAX8902B are packaged in an 8-pin, 2mm x 2mm TDFN package with an exposed paddle. The exposed paddle is the main path for heat to leave the IC, and therefore, must be connected to a ground plane with thermal vias to allow heat to dissipate from the device. Thermal properties of the IC package are given in Table 1. Selecting the Output Voltage (MAX8902A) The MAX8902A output can be set to one of nine volt- ages by shorting or opening the SELA and SELB inputs, as shown in Table 2. SELA and SELB should be connected to GND, IN, or left unconnected. Alternatively, they may be driven high, low, or open with external logic; however, the states of SELA and SELB are sampled only at startup. The regulation voltage can be set to a different level by cycling EN or IN momen- tarily to GND. Setting the Output Voltage (MAX8902B) The MAX8902B uses external feedback resistors to set the output regulation voltage as shown in Figure 3. The output can be set from 0.6V to 5.3V. Set the lower feed- back resistor (R2) to 120k Ω or less to minimize FB input bias current error. Then calculate the value of the upper feedback resistor (R1) as follows: where VFB is the feedback regulation voltage of 0.6V. Power-OK (MAX8902B) The MAX8902B includes an additional open-drain out- put, POK, that pulls low to indicate the output voltage is in regulation. During startup, POK is high impedance until the output voltage rises to 91% of its regulation level. If an overload occurs at the output, or the output is shut down, POK is high impedance. RR V V OUT FB 12 1 =× − ⎛ ⎝⎜ ⎞ ⎠⎟ Low-Noise 500mA LDO Regulators in a 2mm x 2mm TDFN Package _______________________________________________________________________________________ 7 CONTINUOUS POWER DISSIPATION 953.5mW DERATE 11.9mW/°C ABOVE +70°C θJA* 83.9°C/W θJC 36.6°C/W Table 1. 2mm x 2mm TDFN Package Thermal Characteristics OUTPUT VOLTAGE (V) SELA STATE SELB STATE 1.5 IN Unconnected 1.8 Unconnected GND 2.0 Unconnected IN 2.5 Unconnected Unconnected 3.0 GND GND 3.1 GND IN 3.3 GND Unconnected 4.6 IN GND 4.7 IN IN Table 2. MAX8902A Output Voltages * θJA is specified according to the JESD51 standard with the part mounted on a multilayer PCB. |
Similar Part No. - MAX8902A_11 |
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Similar Description - MAX8902A_11 |
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