19-4363; Rev 2; 2/10 50mA to 600mA Programmable Current-Limit Switches The MAX4995A/MAX4995AF/MAX4995AL/MAX4995B/ MAX4995C programmable current-limit switches feature internal current limiting to prevent damage to host devices due to faulty load conditions. These analog switches feature a low 130mΩ (typ) on-resistance and operate from a +1.7V to +5.5V input voltage range. The current limit is adjustable from 50mA to 600mA, making these devices ideal for SDIO (secure digital input/output) and other load-switching applications. Each device in the family handles an overcurrent event differently depending on the option selected. The MAX4995A/MAX4995AF/MAX4995AL go into an autoretry mode, the MAX4995B latches off the switch, and the MAX4995C places the device in a continuous current-limit mode. Additional safety features include thermal shutdown to prevent overheating and reversecurrent blocking to prevent current from being driven back into the source. The MAX4995A/MAX4995AF/MAX4995AL/MAX4995B/ MAX4995C are available in a tiny 10-pin, 1.4mm x 1.8mm UTQFN, a 6-pin SOT23, or an 8-pin, 2mm x 2mm TDFN package and operate over the -40°C to +125°C extended temperature range. Features ♦ 50mA to 600mA Programmable Current Limit ♦ ±10% Accurate Current Limit ♦ Overload FLAG Threshold ♦ Low Dropout Voltage ♦ Short-Circuit Protection ♦ Thermal Shutdown ♦ Reverse-Current Protection ♦ 170µA (typ) Supply Current ♦ +1.7V to +5.5V Supply Voltage Range ♦ Tiny 10-Pin, 1.4mm x 1.8mm UTQFN Package Applications SDIO Ports Cell Phones USB Ports MP3 Players Notebook VGA Ports UTCA/ATCA Platforms GPS Ordering Information/Selector Guide PART PIN-PACKAGE ON POLARITY OVERCURRENT RESPONSE SHORT-CIRCUIT RESPONSE TOP MARK MAX4995AAUT+T* 6 SOT23 Active-High Autoretry Normal +ACNZ MAX4995AAVB+T 10 UTQFN Active-High Autoretry Normal +AAM MAX4995AATA+T 8 TDFN-EP** Active-High Autoretry Normal +ABL MAX4995AFAUT+T* 6 SOT23 Active-High Autoretry Fast +ACOE MAX4995AFAVB+T 10 UTQFN Active-High Autoretry Fast +AAR MAX4995AFATA+T* 8 TDFN-EP** Active-High Autoretry Fast +ACO MAX4995ALAUT+T* 6 SOT23 Active-Low Autoretry Normal +ACDA MAX4995ALAVB+T 10 UTQFN Active-Low Autoretry Normal +AAN MAX4995ALATA+T* 8 TDFN-EP** Active-Low Autoretry Normal +ABM MAX4995BAUT+T* 6 SOT23 Active-High Latchoff Normal +ACDB MAX4995BAVB+T 10 UTQFN Active-High Latchoff Normal +AAO MAX4995BATA+T* 8 TDFN-EP** Active-High Latchoff Normal +ABN MAX4995CAUT+T* 6 SOT23 Active-High Continuous Normal +ACOD MAX4995CAVB+T 10 UTQFN Active-High Continuous Normal +AAQ MAX4995CATA+T* 8 TDFN-EP** Active-High Continuous Normal +ABP All devices operate over the -40°C to +125°C temperature range. +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. *Future product. Contact factory for availability. **EP = Exposed pad. Typical Operating Circuit appears at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX4995A/AF/AL/MAX4995B/MAX4995C General Description MAX4995A/AF/AL/MAX4995B/MAX4995C 50mA to 600mA Programmable Current-Limit Switches ABSOLUTE MAXIMUM RATINGS IN, ON, ON, FLAG, OUT, and SETI to GND .............-0.3V to +6V Current into Any Pin (Except IN, OUT)................................20mA OUT Short Circuit to GND .................................................800mA Continuous Power Dissipation (TA = +70°C) (Note 1) 10-Pin UTQFN (derate 6.99mW/ °C above TA = +70°C) ..559mW 6-Pin SOT23 (derate 13.4mW/ °C above TA = +70°C)...1072.4mW 8-Pin TDFN (derate 11.9mW/ °C above TA = +70°C) ....953.5mW Junction-to-Ambient Thermal Resistance (θJA) (Note 2).....................................................................143.1°C/W Operating Temperature Range .........................-40°C to +125°C Storage Temperature Range .............................-65°C to +150°C Junction Temperature ......................................................+150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: These power limits are defined by the thermal characteristics of the package, maximum function temperature (+150°C), and the JEDEC51-7 defined setup. Maximum power dissipation could be lower, limited by the thermal-shutdown protection included in this IC. Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN = +1.7V to +5.5V, RSETI = 94.3kΩ, CIN = 1µF, and TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at VIN = +3.3V, TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 5.5 V SUPPLY OPERATION Operating Voltage VIN Quiescent Current IQ 1.7 IOUT = 0, switch on, VIN = 3.3V 170 300 μA 8 15 μA Latchoff Current ILATCH VIN = 3.3V, IOUT = 0 after an overcurrent fault (MAX4995B) Shutdown Forward Current ISHDN VON = 0, V ON = VIN, VIN = 5.5V, VOUT = 0 0.01 5 μA IRSHDN VON = 0, V ON = VIN, VIN = 1.7V, VOUT = 5.5V (current into OUT) 0.01 1 μA VIN = 3.3V, IOUT lower than ILIM 130 350 m Shutdown Reverse Current INTERNAL FET Switch-On Resistance RON Normalized Current-Limit Accuracy ILIM = 50mA to 600mA, VIN - VOUT = 1V, VIN = 3.3V (Note 3) 0.9 1 1.1 — (RSETI + 2.48) x ILIM Product ILIM = 50mA to 600mA, VIN - VOUT = 1V, VIN = 3.3V 26138 29042 31946 V Reverse Blocking Current VOUT > VIN + 300mV after reverse-currentlimit shutdown 10 μA Reverse Blocking Threshold VOUT = VIN + 300mV, OUT falling until switch turns on 210 mV FLAG Assertion Drop Voltage Threshold VFA 35 Increase (VIN - VOUT) drop until FLAG asserts, I OUT limiting, VIN = 3.3V 110 650 mV ON, ON INPUT ON, ON Input Leakage ILEAK ON, ON Input Logic-High Voltage VIH ON, ON Input Logic-Low Voltage VIL 2 VON, V ON = VIN or GND -1 +1 μA 0.4 V 1.6 _______________________________________________________________________________________ V 50mA to 600mA Programmable Current-Limit Switches (VIN = +1.7V to +5.5V, RSETI = 94.3kΩ, CIN = 1µF, and TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at VIN = +3.3V, TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.4 V 1 μA FLAG OUTPUT FLAG Output Logic-Low Voltage ISINK = 1mA FLAG Output Leakage Current VIN = VFLAG = 5.5V, FLAG deasserted DYNAMIC Turn-On Time tSS VIN = 3.3V, COUT = 1μF, RL = 20 , Figure 1, (Note 4) 120 μs Turn-Off Time tOFF Switch from on to off, VIN = 3.3V, COUT = 1μF, RL = 20 , Figure 1 (Note 4) 120 μs tLIM VIN = 3.3V, RSETI = 578k , output high and then short-circuit applied Current-Limit Reaction Time MAX4995A/AL/B/C 5 μs MAX4995AF 1.5 Blanking Time tBLANK (Note 5) 10 Retry Time tRETRY MAX4995A/MAX4995AF/MAX4995AL (Note 5) 320 16.3 22.6 ms 723.2 ms THERMAL PROTECTION Thermal Shutdown Thermal-Shutdown Hysteresis +150 °C 15 °C Note 3: ILIM is forward current limit. ILIM (mA) = 29042(V) RSETI (kΩ) + 2.48 (kΩ) Note 4: Turn-on time and turn-off time are defined as the difference in the time between when the output crosses 10% and 90% of the final output voltage. Note 5: Blanking time and retry time are generated by the same oscillator. Therefore, the ratio of t RETRY t BLANK is a constant value of 32. See Figures 2 and 3. tSS 90% 90% VOUT 10% 10% tOFF Figure 1. Timing Diagram for Measuring Turn-On Time (tSS) and Turn-Off Time (tOFF). _______________________________________________________________________________________ 3 MAX4995A/AF/AL/MAX4995B/MAX4995C ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VIN = +3.3V, CIN = 1µF, COUT = 1µF, RSETI = 94.2kΩ, TA = +25°C, unless otherwise noted.) CURRENT LIMIT vs. SUPPLY VOLTAGE NORMALIZED CURRENT LIMIT vs. TEMPERATURE 310 MAX4995AL 1.075 NORMALIZED CURRENT LIMIT MAX4995AL MAX4995A toc02 1.100 MAX4995A toc01 315 CURRENT LIMIT (mA) 305 300 295 1.050 1.025 1.000 0.975 0.950 290 0.925 285 0.900 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 SUPPLY VOLTAGE (V) TEMPERATURE (°C) CURRENT-LIMIT RESPONSE (MAX4995A) CURRENT-LIMIT RESPONSE (MAX4995AF) MAX4995A toc03 MAX4995A toc04 SUDDEN SHORT APPLIED AT OUTPUT SUDDEN SHORT APPLIED AT OUTPUT VOUT (2V/div) VOUT (2V/div) IOUT (10A/div) IOUT (10A/div) 10μs/div 10μs/div QUIESCENT SUPPLY CURRENT vs. SUPPLY VOLTAGE CURRENT-LIMIT RESPONSE MAX4995A toc05 VOUT (2V/div) IOUT (100mA/div) 280 MAX4995A toc06 300 RLOAD = 8Ω QUIESCENT SUPPLY CURRENT (μA) MAX4995A/AF/AL/MAX4995B/MAX4995C 50mA to 600mA Programmable Current-Limit Switches MAX4995A 260 240 220 200 180 160 140 120 4ms/div 100 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) 4 _______________________________________________________________________________________ 5.5 50mA to 600mA Programmable Current-Limit Switches 210 200 190 VIN = 3.3V 170 160 0.75 0.50 VIN = 3.3V MAX4995A toc09 60 50 VIN = 5V 40 30 20 VIN = 1.7V 10 0 TEMPERATURE (°C) TEMPERATURE (°C) SHUTDOWN REVERSE CURRENT vs. TEMPERATURE LATCHOFF CURRENT vs. TEMPERATURE NORMALIZED ON-RESISTANCE vs. SUPPLY VOLTAGE 150 VIN = 5V 125 100 75 50 MAX4995B VIN = 5V 18 16 14 VIN = 3.3V 12 10 VIN = 1.7V 1.040 MAX4995C IOUT < ILIM 1.035 1.030 1.025 1.020 1.015 1.010 1.005 1.000 0.995 0.990 0.985 8 6 0 MAX4995A toc12 20 NORMALIZED ON-RESISTANCE MAX4995C VOUT = 5.5V MAX4995A toc11 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) MAX4995A toc10 0.980 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) TEMPERATURE (°C) SUPPLY VOLTAGE (V) NORMALIZED ON-RESISTANCE vs. TEMPERATURE SWITCH TURN-ON TIME vs. TEMPERATURE SWITCH TURN-OFF TIME vs. TEMPERATURE 1.3 1.2 1.1 1.0 0.9 0.8 180 170 MAX4995C ILOAD = 10mA 160 150 VIN = 5V 140 130 120 0.7 VIN = 3.3V 110 0.6 0.5 2.2 2.7 3.2 3.7 4.2 4.7 5.2 1.6 1.5 MAX4995A toc15 MAX4995C VIN = 3.3V SWITCH TURN-ON TIME (μs) MAX4995A toc13 1.5 1.7 SWITCH TURN-OFF TIME (ms) SHUTDOWN REVERSE CURRENT (nA) VIN = 5V 1.00 70 -40 -25 -10 5 20 35 50 65 80 95 110 125 25 NORMALIZED ON-RESISTANCE 1.25 MAX4995C 0 175 1.4 1.50 80 -40 -25 -10 5 20 35 50 65 80 95 110 125 225 200 1.75 0.25 MAX4995AL 150 140 2.00 MAX4995A toc14 180 MAX4995AL SHUTDOWN FORWARD CURRENT (nA) 230 220 2.25 MAX4995A toc08 240 2.50 SHUTDOWN SUPPLY CURRENT (μA) VIN = 5V LATCHOFF CURRENT (μA) QUIESCENT SUPPLY CURRENT (μA) 260 250 SHUTDOWN FORWARD CURRENT vs. TEMPERATURE SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE MAX4995A toc07 QUIESCENT SUPPLY LIMIT vs. TEMPERATURE MAX4995C ILOAD = 10mA 1.4 VIN = 5V 1.3 1.2 1.1 1.0 0.9 0.8 VIN = 3.3V 0.7 100 0.6 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX4995A/AF/AL/MAX4995B/MAX4995C Typical Operating Characteristics (continued) (VIN = +3.3V, CIN = 1µF, COUT = 1µF, RSETI = 94.2kΩ, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VIN = +3.3V, CIN = 1µF, COUT = 1µF, RSETI = 94.2kΩ, TA = +25°C, unless otherwise noted.) SWITCH TURN-ON TIME RESPONSE SWITCH TURN-OFF TIME RESPONSE MAX4995A toc16 MAX4995A toc17 VON (5V/div) VON (5V/div) VOUT (2V/div) VOUT (2V/div) 200μs/div 200μs/div FLAG RESPONSE (OVERLOAD) CONDITION SWITCH DROPOUT VOLTAGE vs. TEMPERATURE MAX4995A toc18 VOUT (2V/div) VFLAG (2V/div) SWITCH DROPOUT VOLTAGE (mV) IOUT (200mA/div) MAX4995A toc19 19 MAX4995A ILOAD = 100mA 18 17 16 15 14 13 12 11 10 VIN = 3.3V 9 100ms/div -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 1 MAX4995A toc20 MAX4995B 300 250 200 150 100 FLAG (LOGIC-LEVEL STATUS) IOUT/FLAG vs. VDROP (VIN - VOUT) 350 IOUT (mA) MAX4995A/AF/AL/MAX4995B/MAX4995C 50mA to 600mA Programmable Current-Limit Switches 50 VIN = 5.5V 0 0 0 70 140 210 280 350 420 490 560 630 700 VDROP (mV) 6 _______________________________________________________________________________________ 50mA to 600mA Programmable Current-Limit Switches TOP VIEWS IN FLAG IN N.C. OUT OUT N.C. SETI GND 10 9 8 8 7 6 5 1 2 7 MAX4995A/MAX4995AF MAX4995AL/MAX4995B MAX4995C 3 4 ON (ON)* GND 6 OUT 1 GND 2 SETI 3 6 FLAG 5 IN 4 ON (ON)* OUT N.C. MAX4995A/MAX4995AF MAX4995AL/MAX4995B MAX4995C MAX4995A/MAX4995AF MAX4995AL/MAX4995B MAX4995C *EP + 5 SOT23 (1.6mm × 2.9mm) SETI UTQFN (1.4mm × 1.8mm) 1 2 IN IN 3 4 FLAG ON (ON)* TDFN (2mm × 2mm) *( ) FOR THE MAX4995AL ONLY. **EXPOSED PAD. CONNECT EP TO GND. Pin Description PIN (UTQFN) MAX4995AL 1, 10 PIN (TDFN-EP) MAX4995_ 1, 10 MAX4995AL 1, 2 PIN (SOT23) MAX4995_ MAX4995AL 1, 2 5 MAX4995_ 5 NAME FUNCTION 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. 2 2 3 3 6 6 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 — 4 — 4 — ON Active-Low, Switch-On Input. Drive ON low to turn on the switch. — 3 — 4 — 4 ON Active-High, Switch-On Input. Drive ON high to turn on the switch. 4 4 5 5 2 2 GND Ground 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. 5 5 6 6 3 3 _______________________________________________________________________________________ 7 MAX4995A/AF/AL/MAX4995B/MAX4995C Pin Configurations MAX4995A/AF/AL/MAX4995B/MAX4995C 50mA to 600mA Programmable Current-Limit Switches Pin Description (continued) PIN (UTQFN) PIN (TDFN-EP) MAX4995AL MAX4995_ MAX4995AL 6, 9 6, 9 7 PIN (SOT23) MAX4995_ MAX4995AL 7 — MAX4995_ — NAME FUNCTION N.C. No Connect. Not internally connected. Switch Output. Bypass OUT with a 1μF capacitor to ground. Connect both outputs (OUT) together. 7, 8 7, 8 8 8 1 1 OUT — — — — — — EP Exposed Pad. Connect EP to GND. For TDFN package only. Functional Diagram MAX4995A/MAX4995AF/ MAX4995AL/MAX4995B/ MAX4995C REVERSECURRENT PROTECTION IN OUT THERMAL SHUTDOWN UVLO CONTROL LOGIC BUFFER FLAG TIMING CIRCUITRY BANDGAP REFERENCE N.C. SOFT-START CURRENT LIMIT SETI BUFFER ON (ON)* GND *( ) FOR THE MAX4995AL ONLY. 8 _______________________________________________________________________________________ 50mA to 600mA Programmable Current-Limit Switches The MAX4995A/MAX4995AF/MAX4995AL/MAX4995B/ MAX4995C programmable current-limit switches operate 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. Table 1. Switch Truth Table MAX4995_/ MAX4995AF MAX4995AL ON ON 0 1 Off 1 0 On SWITCH STATUS Programmable Current Limit A resistor from SETI to GND programs the current limit for the switch (see the Setting the Current Limit section). 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 present for tBLANK. The timer resets if the overcurrent condition 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 thermal 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 programmed 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 overcurrent condition disappears before t BLANK has elapsed. The switch turns off if the overcurrent condition continues beyond the blanking time. Reset the switch by either toggling the control logic (ON) or cycling the input voltage. If the thermal power rating of the package is exceeded during tBLANK, the MAX4995B goes into thermal shutdown. Continuous Current Limit (MAX4995C) When the forward current reaches the forward currentlimit threshold, the MAX4995C limits the output current to the programmed current limit. FLAG asserts if the current limit is present for tBLANK and deasserts when the overload condition is removed. In this mode, if the thermal power rating of the package is exceeded, the MAX4995C goes into thermal shutdown. Switch-On/Off Control The ON input for the MAX4995_/MAX4995AF and ON input for the MAX4995AL control the switch; see Table 1. Toggle ON for the MAX4995B to reset the fault condition once the short current is detected and the device shuts down. Reverse-Current Protection The MAX4995 features a reverse-current protection circuit that limits the backflow current to 10µA when the output voltage exceeds the input voltage by 110mV (typ). The switch turns off and FLAG asserts without waiting for tBLANK to elapse. The switch turns back on and FLAG deasserts when the output voltage drops below the detecting threshold by 10mV (typ). _______________________________________________________________________________________ 9 MAX4995A/AF/AL/MAX4995B/MAX4995C Detailed Description MAX4995A/AF/AL/MAX4995B/MAX4995C 50mA to 600mA Programmable Current-Limit Switches tBLANK tRETRY tBLANK tRETRY tBLANK tBLANK OUT CURRENT LIMIT THE DEVICE GOES TO THERMAL-SHUTDOWN MODE LOAD CURRENT FLAG Figure 2. Autoretry Fault Diagram tBLANK tBLANK OUT CURRENT LIMIT LOAD CURRENT THE DEVICE GOES TO THERMAL-SHUTDOWN MODE FLAG Figure 3. Latchoff Fault Diagram FLAG Indicator Thermal Shutdown FLAG is an open-drain fault indicator output and requires an external pullup resistor to a DC supply. FLAG goes low when any of the following conditions occurs: Thermal-shutdown circuitry protects the devices from overheating. The switch turns off and FLAG goes low immediately when the junction temperature exceeds +150°C (typ). The switch turns on again after the device temperature drops by approximately 15°C (typ). • The device is in current-limit mode. • The OUT voltage is above the IN voltage by more than 110mV (typ). • The die temperature exceeds the thermal-shutdown temperature limit of +150°C. • SETI is connected to ground. 10 ______________________________________________________________________________________ 50mA to 600mA Programmable Current-Limit Switches Setting the Current Limit A resistor from SETI to ground programs the current-limit value for the MAX4995. Table 2 lists various current limits set by different resistor values at SETI. Shorting SETI to ground asserts FLAG. Use the following formula to calculate the current limit: RSETI (kΩ) = 29042(V) − 2.48 (kΩ) ILIM (mA) Using an RSETI with a value smaller than 45.8kΩ results in a higher current limit. A programmed output current greater than 660mA can damage the device. Connecting any capacitance larger than 20pF to SETI can cause instability. Table 2. Current Limit vs. Resistor Values RSETI (kΩ) TYPICAL CURRENT LIMIT (mA) 45.8 602 55.6 500 70.6 397 94.2 300 143 200 191 150 287 100 576 50 ∞ (Open) 0 Input Capacitor Connect a capacitor from IN to GND to limit the input voltage drop during momentary output short-circuit conditions. Use a 1µF minimum ceramic capacitor for proper device operation. Larger capacitor values reduce the voltage undershoot at the input. Due to the very fast current-limit reaction time of the MAX4995AF, a larger input capacitance might need to be connected at the input to dampen oscillation due to long wires. Choose a value large enough to ensure IN doesn’t exceed the absolute maximum ratings. Output Capacitor For stable operation over the full temperature range and over the full programmable current-limit range, use a 1µF ceramic capacitor from OUT to ground. If the load capacitance is too large, then current may not have enough time to charge the capacitance and the device assumes that there is a faulty load condition. Calculate the maximum capacitive load (CMAX) value that can be connected to OUT using the following formula: C MAX (μ F) = I LIM (mA) × t BLANK(MIN) (ms ) VIN (V) For example, for VIN = 3.3V, tBLANK(MIN) = 10ms, and ILIM = 300mA, CMAX equals 909µF. Due to the very fast current-limit reaction time of the MAX4995AF, a larger output capacitance might need to be connected at the output to dampen oscillation due to long wires. Choose a value large enough to ensure OUT doesn’t exceed the absolute maximum ratings. Layout and Thermal Dissipation To optimize the switch response time to output shortcircuit conditions, it is very important to keep all traces as short as possible to reduce the effect of undesirable parasitic inductance. Place input and output capacitors as close as possible to the device. IN and OUT must be connected with wide, short traces to the power bus. During normal operation, the power dissipation is small and the package temperature change is minimal. If the output is continuously shorted to ground at the maximum supply voltage, the operation of the switches with the autoretry option does not cause problems because the total power dissipated during the short is scaled by the duty cycle: P MAX = VIN(MAX) × I OUT(MAX) × t BLANK t RETRY + t BLANK Attention must be given to the MAX4995C continuous current-limit version when the power dissipation during a fault condition may cause the device to reach thermal shutdown threshold. ______________________________________________________________________________________ 11 MAX4995A/AF/AL/MAX4995B/MAX4995C Applications Information MAX4995A/AF/AL/MAX4995B/MAX4995C 50mA to 600mA Programmable Current-Limit Switches Typical Operating Circuit VCC 1µF VIO IN OUT FLAG 1µF ON (ON*) µP SETI MAX4995A/ MAX4995AF/ MAX4995AL/ MAX4995B/ MAX4995C RSETI LOAD N.C. GND *( ) FOR THE MAX4995AL ONLY. Package Information Chip Information PROCESS: BiCMOS 12 For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 10 UTQFN V101A1CN+1 21-0028 6 SOT23 U6SN+1 21-0058 8 TDFN T822+1 21-0168 ______________________________________________________________________________________ 50mA to 600mA Programmable Current-Limit Switches REVISION NUMBER REVISION DATE 0 11/08 1 6/09 Corrected the Ordering Information/Selector Guide. 2 2/10 • Added TDFN package information to the Ordering Information/Selector Guide, Absolute Maximum Ratings, Pin Description, and Package Information sections. • Added the TDFN pin configuration drawing to the Pin Configurations section. DESCRIPTION Initial release. PAGES CHANGED — 1, 11 1, 2, 7, 12 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13 © 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX4995A/AF/AL/MAX4995B/MAX4995C Revision History