general description the max890l smart, low-voltage, p-channel, mosfet power switch is intended for high-side load-switching applications. this switch operates with inputs from 2.7v to 5.5v, making it ideal for both 3v and 5v systems. internal current-limiting circuitry protects the input sup- ply against overload. thermal-overload protection limits power dissipation and junction temperatures. the max890l? maximum current limit is 1a. the cur- rent limit through the switch is programmed with a resistor from set to ground. the quiescent supply cur- rent is a low 10 m a. when the switch is off, the supply current decreases to 0.1 m a. the max890l is available in an 8-pin so package. ________________________applications pcmcia slots access bus slots portable equipment ____________________________features ? 2.7v to 5.5v input range ? programmable current limit ? low quiescent current 10 m a (typ) at v in = 3.3v 0.1 m a (typ) with switch off ? thermal shutdown ? fault indicator output ? 0.09 (typ) on-resistance max890l 1a, current-limited, high-side p-channel switch with thermal shutdown ________________________________________________________________ maxim integrated products 1 1 2 8 7 fault out out set in in on gnd max890l so top view 3 4 6 5 pin configuration max890l 1 m f 0.1 m f 100k w in output out input in out fault on on/off r set gnd set typical operating circuit 19-1146; rev 2; 11/98 part* max890lc/d 0? to +70? temp. range pin- package dice** ordering information * to order this unit in tape and reel, add (-t) to the end of the part number. ** dice are tested at t a = +25?. current limit 1a 1a max890lesa -40 c to +85? 8 so for free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. for small orders, phone 1-800-835-8769.
max890l 1a, current-limited, high-side p-channel switch with thermal shutdown 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v in = 3v, t a = 0? to +85?, unless otherwise noted. typical values are at t a = +25?.) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. in to gnd ..................................................................-0.3v to 6v on , fault to gnd ....................................................-0.3v to 6v set, out to gnd ...................................... -0.3v to (v in + 0.3v) maximum continuous switch current ..................................1.5a continuous power dissipation (t a = +70?) so (derate 5.88mw/? above +70?) ..........................471mw operating temperature range max890lesa ....................................................-40? to +85? storage temperature range ........................... -65? to +150? lead temperature (soldering, 10sec) . ...........................+300? on = in, v in = v out = 5.5v v in = 5v v in = 3v, i out = 500ma v in = 5v, on = gnd, i out = 0 v in = 5v, i out = 500ma 20% current overdrive, v cc = 5v v fault = 5.5v, v set = 1v v in = 2.7v to 3.6v v in = 2.7v to 5.5v i sink = 1ma, v set = 1.4v v set = 1.24v, i out = 0; v in = v out i out = 500ma, v out > 1.6v on = in, v in = 5.5v, v out = 0 rising edge, 1% hysteresis v in = 4.5v v on = 5.5v v set required to turn the switch off (note 1) v in = 4.5v to 5.5v conditions ? 25 turn-off time ? 185 turn-on time 120 200 ? 2 fast-current-loop response time ? 5 slow-current-loop response time ? 0.05 1 fault logic output high leakage current v 0.4 fault logic output low voltage ? 0.5 3 i set bias current ? 0.01 1 on input leakage v 2.4 on input high voltage ? 0.03 1 off-supply current ? 13 20 v 2.7 5.5 operating voltage quiescent current 2.0 v 0.8 on input low voltage a/a 970 1110 1300 i out to i set current ratio a 1 maximum output current limit ? 0.04 15 off-switch current v 2.0 2.4 2.6 undervoltage lockout 75 130 v 1.178 1.240 1.302 current-limit-amplifier threshold units min typ max parameter v in = 3.0v m 90 150 on-resistance note 1: tested with i out = 100ma and v set raised until v in - v out 3 0.8v.
max890l 1a, current-limited, high-side p-channel switch with thermal shutdown _______________________________________________________________________________________ 3 note 2: specifications to -40? are guaranteed by design, not production tested. on = in, v in = v out = 5.5v v in = 5v v in = 5v, on = gnd, i out = 0 i sink = 1ma, v set = 1v i out = 500ma, v out > 1.6v on = in, v in = 5.5v, v out = 0 rising edge, 1% hysteresis v in = 4.5v v set required to turn the switch off (note 1) conditions v in = 3.0v m 150 ? 200 on-resistance turn-on time v 0.4 fault logic output low voltage ? 2.2 off-supply current ? 50 v 2.9 5.5 operating voltage quiescent current a/a 925 1390 i out to i set current ratio ? 15 off-switch current v 2.0 2.9 undervoltage lockout 130 v 1.14 1.34 current-limit-amplifier threshold units min typ max parameter electrical characteristics (v in = 3v, t a = -40? to +85?, unless otherwise noted.) (note 2) v in = 5v ? 120 turn-off time
max890l 1a, current-limited, high-side p-channel switch with thermal shutdown 4 _______________________________________________________________________________________ -40 0 20 60 80 40 -20 100 off-switch current vs. temperature max890l toc04 temperature (?) off-switch current (na) 1000 0.01 1 10 0.1 100 0.6 -40 -20 40 20 100 normalized on-resistance vs. temperature 0.8 max890-05 temperature (?) normalized r on 06080 1.2 1.0 0.7 1.3 1.1 0.9 i out = 1/2i limit 0 020 80 60 140 i out /i set ratio vs. i limit 400 max890-06 i limit (%) i out /i set ratio 40 100 120 1200 800 200 1400 1000 600 0 0.2 0.4 0.6 0.8 1.0 1.2 normalized output current vs. output voltage max890-06a output voltage (v) normalized output current 01 234 56 i limit v in = 5v 260 60 turn-on time vs. temperature 100 220 max980-07 temperature (?) t on ( m s) 180 140 240 80 200 160 120 i load = i limit v in = 3v v in = 5v -40 -20 40 20 100 06080 0 turn-off time vs. temperature 2 8 max980-08 temperature (?) t off ( m s) 6 4 1 7 5 3 i load = i limit v in = 3v v in = 5v -40 -20 40 20 100 06080 __________________________________________typical operating characteristics (t a = +25?, unless otherwise noted.) 0 2 4 6 8 10 12 14 quiescent current vs. input voltage max890-01 input voltage (v) 01 234 56 on = gnd i out = 0 quiescent current ( m a) 7 -40 -20 40 20 100 quiescent current vs. temperature 9 max890-02 temperature (?) quiescent current ( m a) 06080 13 11 8 14 12 10 v in = 3v v in = 5v 100 0.01 -40 -20 20 060 40 80 100 off-supply current vs. temperature 0.1 max890l toc03 temperature (?) off-supply current (na) 1 10
v in = 5v, i out = i limit a: v on , 2v/div b: v out , 2v/div switch turn-on time a b 20?/div switch turn-off time a b 0v 0v 2?/div v in = 5v, i out = i limit a: v on , 2v/div b: v out , 2v/div v in = 5v a: i out = 0ma to 750ma, 0.5a/div load-transient response a b 0a 0v 5ms/div b: v out ripple, 200mv/div, ac coupled c in = 100?, c out = 0.1? a: v in , 1v/div, ac coupled current-limit response (r l = 0.3 w ) a5v b c 0v 2?/div 0a b: i out , 5a/div c: v out , 2v/div c in = 100?, c out = 0.1? a: v in , 1v/div, ac coupled current-limit response (r l = 0.6 w ) a5v b c 0v, 0a 2?/div b: i out , 1a/div c: v out , 2v/div max890l 1a, current-limited, high-side p-channel switch with thermal shutdown _______________________________________________________________________________________ 5 ____________________________typical operating characteristics (continued) (t a = +25?, unless otherwise noted.)
max890l 1a, current-limited, high-side p-channel switch with thermal shutdown 6 _______________________________________________________________________________________ pin description switch output. p-channel mosfet drain. bypass out with a 0.1 m f capacitor to ground. out 6, 7 fault-indicator output. this open-drain output goes low when in current limit or when the die temperature exceeds +135?. fault 8 set current-limit input. a resistor from set to ground sets the current limit for the switch. r set = 1.38 x 10 3 / i limit, where i limit is the desired current limit in amperes. set 5 ground gnd 4 pin active-low switch on input. a logic low turns the switch on. on 3 input. p-channel mosfet source. bypass in with a 1 m f capacitor to ground. in 1, 2 function name detailed description the max890l p-channel mosfet power switch limits output current to a programmed level. when the output current is increased beyond the programmed current limit, or 1a (i max ), the current also increases through the replica switch (i out /1110) and through r set (figure 1). the current-limit error amplifier compares the voltage across r set to the internal 1.24v reference, and regulates the current back to the lesser of the pro- grammed limit (i limit ) or 1a. this switch is not bidirectional; therefore, the input volt- age must be higher than the output voltage. setting the current limit the max890l features internal current-limiting circuitry with a maximum programmable value (i max ) of 1a. for best performance, set the current limit (i limit ) between 0.2 i max i limit i max . this current limit remains in effect throughout the input supply-voltage range. program the current limit with a resistor (r set ) from set to ground (figure 2) as follows: i set = i limit / 1110 r set = 1.24v / i 8 = 1.38 x 10 3 / i limit where i limit is the desired current limit. short-circuit protection the max890l is a short-circuit-protected switch. in the event of an output short circuit or current-overload con- dition, the current through the switch is limited by the internal current-limiting error amplifier to 1.5 x i limit . when the fault condition is removed, the replica error amplifier will set the current limit back to i limit . for a high dv ds /dt during an output short-circuit condi- tion, the switch turns off and disconnects the input supply from the output. the current-limiting amplifier then slow- ly turns the switch on with the output current limited to 1.5 x i limit . when the fault condition is removed, the current limit is set back to i limit . refer to output short- circuit fast-loop response and output short-circuit slow-loop response in the typical operating characteristics . max890l p p p r set set out gnd 1.24v n fault on on current-limit amplifier replica amplifier on hot in control circuitry figure 1. functional diagram
max890l 1a, current-limited, high-side p-channel switch with thermal shutdown _______________________________________________________________________________________ 7 thermal shutdown the max890l features thermal shutdown. the switch turns off when the junction temperature exceeds +135?. once the device cools by 10?, the switch turns back on. if the fault short-circuit condition is not removed, the switch will cycle on and off, resulting in a pulsed output. fault indicator the max890l provides a fault output ( fault ). this open-drain output goes low when in current limit or when the die temperature exceeds +135?. a 100k pull-up resistor from fault to in provides a logic- control signal. applications information input capacitor to limit the input voltage drop during momentary output short-circuit conditions, connect a capacitor from in to gnd. a 1? ceramic capacitor will be adequate for most applications; however, higher capacitor values will further reduce the voltage drop at the input. output capacitor connect a 0.1? capacitor from out to gnd. one function of this capacitor is to prevent inductive para- sitics from pulling out negative during turn-off. layout and thermal-dissipation consideration to take full advantage of the switch-response time to output short-circuit 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). under normal operating conditions, the package can dissipate and channel heat away. calculate the maxi- mum power as follows: p = i 2 limit x r on where r on is the on-resistance of the switch. when the output is short circuited, the voltage drop across the switch equals the input supply. hence, the power dissipated across the switch increases, as does the die temperature. if the fault condition is not removed, the thermal-overload-protection circuitry turns the switch off until the die temperature falls by 10?. a ground plane in contact with the device will help dissi- pate additional heat. chip information transistor count: 396 max890l set r set gnd figure 2. setting the current limit
max890l 1a, current-limited, high-side p-channel switch with thermal shutdown ________________________________________________________package information maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 8 _____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 1998 maxim integrated products printed usa is a registered trademark of maxim integrated products. soicn.eps
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