19-2944; Rev 0; 8/03 450mA/500mA Current-Limit Switches The MAX4796 and MAX4798 have an autoretry feature where the switch turns off and issues a FLAG to the microprocessor after the blanking time and then continuously checks to see if the overload condition is present. The switch remains on after the overload condition disappears and FLAG deasserts. The MAX4795–MAX4798 are available in tiny, spacesaving, 5-pin SOT23 and 6-pin TDFN (3mm x 3mm) packages. Applications SDIO PDAs and Palmtop Devices Cell Phones Features ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ Guaranteed Current Limit: 450mA and 500mA Thermal-Shutdown Protection Reverse-Current Protection 0.2Ω On-Resistance 14ms Guaranteed Blanking Time FLAG Function Autoretry (MAX4796/MAX4798) 80µA Supply Current 6µA Latchoff Current (MAX4795/MAX4797) 0.01µA Shutdown Current +2V to +4.5V Supply Range Fast Current-Limit Response Time Tiny SOT23 and TDFN Packages UL Certification Pending Ordering Information PART TEMP RANGE PINPACKAGE TOP MARK AEDI MAX4795EUK-T -40°C to +85°C 5 SOT23-5 MAX4795ETT* 40°C to +85°C 6 TDFN-EP** MAX4796EUK-T -40°C to +85°C 5 SOT23-5 MAX4796ETT* -40°C to +85°C 6 TDFN-EP** MAX4797EUK-T -40°C to +85°C 5 SOT23-5 MAX4797ETT* -40°C to +85°C 6 TDFN-EP** GPS Systems MAX4798EUK-T -40°C to +85°C 5 SOT23-5 Hand-Held Devices MAX4798ETT* -40°C to +85°C 6 TDFN-EP** Typical Operating Circuit — AEDJ — AEDK — AEDL — *Future product—contact factory for availability. **EP = Exposed pad. Selector Guide appears at end of data sheet. +2.0V TO +4.5V Pin Configurations TOP VIEW IN ON MAX4795 MAX4796 MAX4797 MAX4798 µP FLAG IN 1 GND 2 TO SDIO PORT OUT ON 3 5 OUT MAX4795 MAX4796 MAX4797 MAX4798 IN 1 OUT 2 4 FLAG N.C. 3 6 ON MAX4795 MAX4796 MAX4797 MAX4798 5 GND 4 FLAG GND SOT23 TDFN ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX4795–MAX4798 General Description The MAX4795–MAX4798 family of switches feature internal current limiting to prevent damage to host devices due to faulty load conditions. These analog switches have a low 0.2Ω on-resistance and operate from a 2.0V to 4.5V input voltage range. They are available with guaranteed 450mA and 500mA current limits, making them ideal for SDIO and other load-switching applications. When the switch is on and a load is connected to the port, a guaranteed blanking time of 14ms ensures the transient voltages settle down. If after this blanking time, the load current is greater than the current limit, the MAX4795 and MAX4797 switches are turned off and FLAG is issued to the microprocessor. The switch can be turned on again by cycling the power or the ON input. MAX4795–MAX4798 450mA/500mA Current-Limit Switches ABSOLUTE MAXIMUM RATINGS IN, ON, FLAG, OUT to GND .....................................-0.3V to +6V OUT Short Circuit to GND .................................Internally Limited Continuous Power Dissipation (TA = +70°C) 5-Pin SOT23 (derate 7.1mW/°C above +70°C)............571mW 6-Pin TDFN (derate 24.4mW/°C above +70°C) .........1951mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C 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 = +2.0V to +4.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VIN = 3.3V, TA = +25°C.) (Note 1) PARAMETER SYMBOL Operating Voltage VIN Quiescent Current IQ CONDITIONS 125 µA VIN = +3.3V 6 10 µA 1 µA ISHDN VON = 0V 0.03 MAX4795/MAX4796, VIN = 3.3V, VOUT = GND 450 720 MAX4797/MAX4798, VIN = 3.3V, VOUT = GND 500 800 MAX4795/MAX4796 720 MAX4797/MAX4798 800 ON Input Leakage -1 Shutdown Forward Leakage VON = 0V, VOUT = 0V Shutdown Reverse Leakage VON = 0V, VIN = 2V, VOUT = 4.5V ON Input Logic High Voltage VIH ON Input Logic Low Voltage VIL V 80 Shutdown Current RON UNITS 4.5 VIN = +3.3V ILATCH On-Resistance (Note 3) MAX VON = VIN, IOUT = 0, switch on Latch-Off Current Reverse Current Limit TYP 2.0 VON = VIN, after an overcurrent fault (MAX4795/MAX4797) (Note 2) Forward Current Limit MIN +1 0.01 µA µA 0.2 0.4 0.18 0.36 FLAG Output Logic Low Voltage ISINK = 1mA FLAG Output High Leakage Current VIN = V F LAG = VON = 4.5V µA 1 MAX4797/MAX4798, ILOAD = 100mA VIN > 3.6V mA 1 MAX4795/MAX4796, ILOAD = 100mA VIN = +2V to +3.6V mA 1.4 Ω V 2 0.5 V 0.4 V 1 µA Thermal Shutdown 150 °C Thermal-Shutdown Hysteresis 15 °C µs DYNAMIC Turn-On Time VON from low to high; IOUT = 10mA, CL = 0.1µF (Note 4) 120 Turn-Off Time VON from high to low; IOUT = 10mA, CL = 0.1µF (Note 4) 100 Blanking Time tBLANK Short-Circuit Current-Limit Response Time Retry Time Overcurrent fault; Figures 2, 3 14 VON = VIN, short circuit applied to OUT tRETRY MAX4796/MAX4798, Figure 2 (Note 5) ns 60 5 210 ms µs 900 ms All parts are 100% tested at +25°C. Electrical limits across the full temperature range are guaranteed by design and correlation. Latch-off current does not include the current flowing into FLAG. TDFN packages are guaranteed by design. The on-time is defined as the time taken for the current through the switch to go from 0mA to full load. The off-time is defined as the time taken for the current through the switch to go from full load to 0mA. Note 5: Retry time is typically 15 times the blanking time. 2 _______________________________________________________________________________________ Note 1: Note 2: Note 3: Note 4: 450mA/500mA Current-Limit Switches 80 60 40 9 LATCH-OFF CURRENT (µA) 100 VON = VIN 90 SUPPLY CURRENT (µA) 120 10 MAX4795 toc02 VON = VIN 140 80 70 7 6 5 4 3 1 0 0 50 2.5 3.0 3.5 4.0 4.5 -40 -15 35 60 -15 10 35 60 SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE SHUTDOWN LEAKAGE CURRENT vs. TEMPERATURE LATCH-OFF LEAKAGE CURRENT vs. TEMPERATURE 0.1 0.01 1 0.1 0.01 0.001 0.001 -15 10 35 60 -15 SHUTDOWN REVERSE LEAKAGE CURRENT vs. TEMPERATURE 0.1 0.01 0.001 60 85 -40 -15 10 35 TEMPERATURE (°C) NORMALIZED ON-RESISTANCE vs. TEMPERATURE OUTPUT CURRENT vs. OUTPUT VOLTAGE MAX4795 toc08 1.0 0.8 0.6 0.4 60 1000 900 800 OUTPUT CURRENT (mA) 0.01 35 1.2 NORMALIZED RON (Ω) 0.1 10 1.4 MAX4795 toc07 1 1 TEMPERATURE (°C) TEMPERATURE (°C) VON = 0V, VOUT = 4.5V 10 0.0001 -40 85 100 85 MAX4795 toc06 VON = 0V, VOUT = 0V LATCH-OFF LEAKAGE CURRENT (nA) MAX4795 toc04 1 10 MAX4795 toc05 TEMPERATURE (°C) 10 -40 -40 85 TEMPERATURE (°C) 100 10 10 SUPPLY VOLTAGE (V) SHUTDOWN SUPPLY CURRENT (nA) 2.0 SHUTDOWN SUPPLY CURRENT (nA) 8 2 60 20 SHUTDOWN LEAKAGE CURRENT (nA) VON = VIN 700 85 MAX4795 toc09 SUPPLY CURRENT (µA) 100 MAX4795 toc01 160 LATCH-OFF CURRENT vs. TEMPERATURE SUPPLY CURRENT vs. TEMPERATURE MAX4795 toc03 QUIESCENT SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX4797/MAX4798 600 500 400 MAX4795/MAX4796 300 200 0.001 0.2 100 0 0 0.0001 -40 -15 10 35 TEMPERATURE (°C) 60 85 -40 -15 10 35 TEMPERATURE (°C) 60 85 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 3.3 VIN - VOUT (V) _______________________________________________________________________________________ 3 MAX4795–MAX4798 Typical Operating Characteristics (VIN = 3.3V, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VIN = 3.3V, TA = +25°C, unless otherwise noted.) FORWARD CURRENT LIMIT vs. SUPPLY VOLTAGE FLAG-BLANKING TIMEOUT vs. TEMPERATURE SWITCH TURN-ON/OFF TIMES vs. TEMPERATURE 100 TURN-ON/OFF TIMES (µs) MAX4797/MAX4798 600 575 550 MAX4795/MAX4796 525 ON 10 1 0.1 2.5 3.0 3.5 4.5 4.0 40 35 30 20 0.001 2.0 45 25 OFF 0.01 500 50 MAX4795 toc12 625 ILOAD = 10mA FLAG-BLANKING TIMEOUT (ms) OUT = GND MAX4795 toc11 1000 MAX4795 toc10 650 FORWARD CURRENT LIMIT (mA) MAX4795–MAX4798 450mA/500mA Current-Limit Switches -40 -15 10 35 60 -40 85 -15 10 TEMPERATURE (°C) MAX4797/MAX4798 CURRENT-LIMIT RESPONSE MAX4797/MAX4798 CURRENT-LIMIT RESPONSE CURRENT-LIMIT RESPONSE (OUT SHORTED TO GND) 3V 3.3V VIN 2V/div VIN = VON 1V/div VIN 2V/div 0V 3.3V VON 2V/div 0V 0V 3.3V VOUT 2V/div 0V 0V IOUT 200mA/div VIN = 3.3V COUT = 1µF CIN = 1µF VSEL = 3.3V 85 MAX4795 toc15 MAX4795 toc14 3.3V IOUT 200mA/div CIN = 1µF COUT = 1µF VIN = VON COUT = 1µF CIN = 1µF 0V 40µs/div IOUT 5A/div 0V 4µs/div 40µs/div MAX4797/MAX4798 REVERSE CURRENT LIMIT SWITCH TURN-ON TIME RESPONSE MAX4795 toc16 MAX4795 toc17 VIN 2V/div 3V 0V 3V 3V VIN = 3.3V VON 1V/div VOUT 2V/div 0V 0V IOUT 1A/div 0V CIN = 1µF COUT = 1µF IOUT 10mA/div 0V 200µs/div 4 60 TEMPERATURE (°C) MAX4795 toc13 0V 35 SUPPLY VOLTAGE (V) 20µs/div _______________________________________________________________________________________ 450mA/500mA Current-Limit Switches MAX4797/MAX4798 FLAG-BLANKING RESPONSE (OVERLOAD CONDITION) SWITCH TURN-OFF TIME RESPONSE MAX4795 toc18 MAX4795 toc19 3.3V 3.3V VON 1V/div VIN 2V/div 0V 3.3V VOUT 2V/div 0V 3.3V 0V IOUT 10mA/div 0V VFLAG 2V/div 0V VIN = 3.3V CIN = 1µF COUT = 1µF 0V 40ns/div IOUT 500mA/div 10ms/div Pin Description PIN SOT23 TDFN NAME FLAG 1 1 IN 2 5 GND 3 4 6 4 REVERSE-CURRENT DETECTOR FUNCTION BLANKING TIME CIRCUITRY Input. Bypass with a 0.1µF ceramic capacitor to ground. Ground ON Active-High Switch On Input. A logic high turns the switch on. FLAG Fault Output. This open-drain output goes low when the device stays in forward or reverse current limit for more than the blanking time period. FLAG is high impedance when a fault is not present or when ON is low. 5 2 OUT Switch Output. Bypass with a 0.1µF ceramic capacitor to ground. — 3 N.C. No Connection. Not internally connected. FORWARD-CURRENT DETECTOR N IN OUT ON GND LOGIC AUTORETRY MAX4795–MAX4798 Figure 1. Functional Diagram _______________________________________________________________________________________ 5 MAX4795–MAX4798 Typical Operating Characteristics (continued) (VIN = 3.3V, TA = +25°C, unless otherwise noted.) MAX4795–MAX4798 450mA/500mA Current-Limit Switches Detailed Description FLAG Indicator The MAX4795–MAX4798 are forward/reverse currentlimited switches that operate from a 2V to 4.5V input voltage range and guarantee a 450mA and 500mA minimum current-limit threshold for different options. The voltage drop across an internal sense resistor is compared to two reference voltages to indicate a forward or reverse current-limit fault. When the load current exceeds the preset current limit for greater than the fault-blanking time, the switch opens. The MAX4795–MAX4798 feature a latched output (FLAG). Whenever an overcurrent condition is encountered, the MAX4795/MAX4797 latch FLAG low and turn the switch off. The MAX4796/MAX4798 latch FLAG low and keep it low until the overcurrent condition is removed. During this time, the switch cycles on and off in the autoretry mode. When the overcurrent condition is removed, FLAG deasserts and the switch turns on (Figure 2). FLAG is an open-drain output transistor and requires an external pullup resistor from FLAG to IN. During shutdown (ON is low), the pulldown on FLAG output is released to limit power dissipation. FLAG goes low when any of the following conditions occur: • The die temperature exceeds the thermal-shutdown temperature limit of +150°C. The MAX4796 and MAX4798 have an autoretry function that turns on the switch again after an internal retry time expires. If the faulty load condition is still present after the blanking time, the switch turns off again and the cycle is repeated. If the faulty load condition is not present, the switch remains on. The MAX4795 and MAX4797 do not have the autoretry option and the switch remains in latch-off mode until the ON pin or the input power is cycled from high to low and then high again. • The device is in current limit for more than the faultblanking period. • The switch is in autoretry. Reverse-Current Protection tBLANK The MAX4795–MAX4798 limit the reverse current (VOUT to VIN) from exceeding the maximum IREV value. The switch is shut off and FLAG is asserted if the reverse current-limit condition persists for more than the blanking time. This feature prevents excessive reverse currents from flowing through the device. Switch-On/Off Control Toggle ON high to enable the current-limited switches. The switches are continuously on if there is no fault. When a forward/reverse current fault is present or the die exceeds the thermal-shutdown temperature of +150°C, OUT is internally disconnected from IN and the supply current decreases to 8µA (latch off). The switch is now operating in one of its off states. The switch-off state also occurs when driving ON low, thus reducing the supply current (shutdown) to 0.01µA. Table 1 illustrates the ON/OFF state of the MAX4795–MAX4798 current-limit switches. tRETRY tBLANK tBLANK CURRENT LIMIT SHORT CONDITION REMOVED ON SWITCH STATUS OFF FLAG PIN STATUS Figure 2. MAX4796/MAX4798 Autoretry Fault-Blanking Diagram Table 1. MAX4795–MAX4798 Switch Truth Table 6 ON FAULT Low X High Thermal High Current limit SWITCH ON/OFF SUPPLY CURRENT MODE OFF Shutdown OFF immediately (tBLANK period does not apply) Latchoff OFF after tBLANK period has elapsed Latchoff ON during tBLANK period, OFF during tRETRY period for the MAX4796 and MAX4798; cycle repeats until fault is removed See the Autoretry section _______________________________________________________________________________________ 450mA/500mA Current-Limit Switches Latchoff (MAX4795/MAX4797) When the forward or reverse current-limit threshold is exceeded, tBLANK timer begins counting. The timer resets if the overcurrent condition disappears before tBLANK has elapsed. The switch is shut off and FLAG asserts if the overcurrent condition continues up to the end of the blanking time. Reset the switch by either toggling ON (Figure 3) or cycling the input voltage. Fault Blanking The MAX4795–MAX4798 feature 14ms (min) fault blanking. Fault blanking allows current-limit faults, including momentary short-circuit faults that occur when hot swapping a capacitive load, and also ensures that no fault is issued during power-up. When a load transient causes the device to enter current limit, an internal counter starts. If the load-transient fault persists beyond the fault-blanking timeout, FLAG asserts low. Load-transient faults less than tBLANK do not cause a FLAG output assertion. Only current-limit faults are blanked. A thermal fault causes FLAG to assert immediately and does not wait for the blanking time. Thermal Shutdown The MAX4795–MAX4798 have a thermal-shutdown feature to protect the devices from overheating. The switch tBLANK MAX4795–MAX4798 Autoretry (MAX4796/MAX4798) When the forward or reverse current-limit threshold is exceeded, tBLANK timer begins counting (Figure 2). The timer resets if the overcurrent condition disappears before tBLANK has elapsed. A retry time delay, tRETRY, is started immediately after tBLANK has elapsed and during that time, the switch is latched off and FLAG asserts. At the end of tRETRY, the switch is turned on again. If the fault still exists, the cycle is repeated. If the fault has been removed, the switch stays on and FLAG deasserts. The autoretry feature saves system power in the case of an overcurrent or short-circuit condition. During tBLANK, when the switch is on, the supply current is at the current limit. During tRETRY, when the switch is off, the current through the switch is zero. Instead of observing the full load current, the switch sees the equivalent load current times duty cycle or ISUPPLY = I LOAD ✕ t BLANK /(t BLANK + t RETRY ). With a typical tBLANK = 37ms and typical tRETRY = 555ms, the duty cycle is 6%, which results in a 94% power savings over the switch being on the entire time. The duty cycle is consistent across the process and devices. tBLANK LOAD CURRENT ON SWITCH STATUS OFF ON PIN VOLTAGE FLAG PIN STATUS (a) tBLANK tBLANK LOAD CURRENT ON SWITCH STATUS OFF IN PIN VOLTAGE FLAG PIN STATUS Figure 3. MAX4795/MAX4797 Latch-Off Fault Blanking turns off and FLAG goes low immediately (no fault blanking) when the junction temperature exceeds +150°C. The switches with autoretry turn back on when the device temperature drops approximately 15°C. The switches with latchoff require ON cycling. Applications Information Input Capacitor To limit the input voltage drop during momentary output short-circuit conditions, connect a capacitor from IN to GND. A 0.1µF ceramic capacitor is adequate for most applications; however, higher capacitor values further reduce the voltage drop at the input and are recommended for lower voltage applications. _______________________________________________________________________________________ 7 MAX4795–MAX4798 450mA/500mA Current-Limit Switches Output Capacitance Connect a 0.1µF capacitor from OUT to GND. This capacitor helps prevent inductive parasitics from pulling OUT negative during turn off, thus preventing the MAX4795–MAX4798 from tripping erroneously. If the load capacitance is too large, then current may not have enough time to charge the capacitor and the device assumes that there is a faulty load condition. The maximum capacitive load value that can be driven from OUT is obtained by the following formula: CMAX < IFWD _ MIN × tBLANK _ MIN VIN 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 (no more than 5mm). IN and OUT pins must be connected with short traces to the power bus. Selector Guide PART CURRENT LIMIT (mA) PMAX = VIN _ MAX × IOUT _ MAX × tBLANK tRETRY + tBLANK 450 No MAX4795ETT 450 No MAX4796EUK-T 450 Yes MAX4796ETT 450 Yes MAX4797EUK-T 500 No MAX4797ETT 500 No MAX4798EUK-T 500 Yes MAX4798ETT 500 Yes = 211mW where VIN = 4.5V, IOUT = 750mA, tBLANK = 14ms, and tRETRY = 210ms. Attention must be given to the MAX4795 and MAX4797 where the latchoff condition must be manually reset by toggling ON from high to low. If the latchoff time duration is not sufficiently high, it is possible for the device to reach the thermal-shutdown threshold and never be able to turn the device on until it cools down. Chip Information TRANSISTOR COUNT: 2539 PROCESS: BiCMOS AUTORETRY MAX4795EUK-T 8 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: _______________________________________________________________________________________ 450mA/500mA Current-Limit Switches SOT-23 5L .EPS PACKAGE OUTLINE, SOT-23, 5L 21-0057 E 1 1 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 _____________________ 9 © 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX4795–MAX4798 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)