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MAX4995BAVB+T Datasheet(PDF) 7 Page - Maxim Integrated Products |
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MAX4995BAVB+T Datasheet(HTML) 7 Page - Maxim Integrated Products |
7 / 13 page 50mA to 600mA Programmable Current-Limit Switches _______________________________________________________________________________________ 7 Detailed Description The MAX4995A/MAX4995AF/MAX4995AL/MAX4995B/ MAX4995C programmable current-limit switches oper- ate from +1.7V to +5.5V and provide internal current limiting adjustable from 50mA to 600mA. These devices feature a fixed blanking time and a FLAG output that notifies the processor when a fault condition is present. Programmable Current Limit A resistor from SETI to GND programs the current limit for the switch (see the Setting the Current Limit sec- tion). If the output current exceeds the current limit for a time equal to or longer than tBLANK, the output flag asserts and the MAX4995A/MAX4995AF/MAX4995AL enter the autoretry mode. The MAX4995B latches off the switch, and the MAX4995C enters the continuous current-limit mode. Autoretry (MAX4995A/MAX4995AF/ MAX4995AL) When the forward current reaches the current-limit threshold, the tBLANK timer begins counting (Figure 2). FLAG asserts if the overcurrent-limit condition is pre- sent for tBLANK. The timer resets if the overcurrent con- dition disappears before the blanking time (tBLANK) has elapsed. A retry time delay (tRETRY) starts immediately after the blanking time has elapsed and during that time, the switch latches off. At the end of tRETRY, the switch turns on again. If the fault still exists, the cycle repeats. If the fault has been removed, the switch stays on. During this cycle, FLAG stays low. In autoretry if the thermal power rating of the package is exceeded, the MAX4995A/MAX4995AF/MAX4995AL go into ther- mal shutdown. The autoretry feature saves system power in case of an overcurrent or short-circuit condition. During tBLANK time when the switch is on, the supply current is held at the current limit. During time tRETRY when the switch is off, the current through the switch is zero. Thus, the average output current is much less than the pro- grammed current limit. Calculate the average output current using the following equation: ILOAD = ILIM [tBLANK/(tBLANK + tRETRY)] With a typical tBLANK = 16.3ms and typical tRETRY = 524ms, the duty cycle is 3%, resulting in a 97% power savings over the switch being on the entire time. Latchoff (MAX4995B) When the forward current reaches the current-limit threshold, the tBLANK timer begins counting (Figure 3). FLAG asserts if an overcurrent-limit condition is present for greater than tBLANK time. The timer resets if the over- current condition disappears before tBLANK has elapsed. The switch turns off if the overcurrent condition Pin Description PIN (UTQFN) MAX4995AL MAX4995_ NAME FUNCTION 1, 10 1, 10 IN Power Input. Bypass IN with a 1µF ceramic capacitor to ground. Use higher capacitance to prevent large load transients from pulling down the supply voltage if necessary. Connect both power inputs (IN) together. 22 FLAG Open-Drain, Overload Indicator Output. FLAG goes low when the overload fault duration exceeds the blanking time, reverse current is detected, thermal shutdown mode is active, or SETI is connected to ground. 3— ON Active-Low, Switch-On Input. Drive ON low to turn on the switch. — 3 ON Active-High, Switch-On Input. Drive ON high to turn on the switch. 4 4 GND Ground 5 5 SETI Overload Current Limit Adjust. Connect a resistor from SETI to ground to program the overcurrent limit. Do not connect any capacitance larger than 20pF to SETI. 6, 9 6, 9 N.C. No Connect. Not internally connected. 7, 8 7, 8 OUT Switch Output. Bypass OUT with a 1µF capacitor to ground. Connect both outputs (OUT) together. |
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Similar Description - MAX4995BAVB+T |
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