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mic2544/2548 programmable current limit high-side switch micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 ( 408 ) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micrel.com april 2010 m9999-043010 general description the mic2544 and mic2548 are integrated, high-side power switches optimized for low loss dc power switching and other power management applications, including advanced configuration and power interface (acpi). the mic2544/48 is a cost-effective, highly integrated solution that requires few external components to satisfy usb and acpi requirements. load current management features include a precision resistor-programmable output current-limit and a soft-start circuit which minimizes inrush current when the switch is enabled. thermal shutdown, along with current-limit, protects the switch and the attached device. the mic2544/48?s open-drain flag output is used to indicate current-limiting or thermal shutdown to a local controller. the mic2548 has an additional internal latch which turns the output off upon thermal shutdown providing robust fault control. the enable signal is compatible with both 3v and 5v logic, and is also used as the thermal shutdown latch reset for the mic2548. the mic2544 and mic2548 are available in active-high and active-low enable versions in the 8-pin soic (small-outline integrated circuit) and 8-pin msop (micro- small-outline package). features ? 2.7v to 5.5v input ? adjustable current-limit up to 1.5a ? reverse current flow blocking (no ?body diode?) ? 75 a typical on-state supply current ? 1 a typical off-state supply current ? 120m maximum on-resistance ? open-drain fault flag ? thermal shutdown ? thermal shutdown output latch (mic2548) ? 2ms (slow) turn-on and fast turnoff ? available with active-high or active-low enable applications ? usb power distribution ? pci bus power switching ? notebook pc ? acpi power distribution ? pc card hot swap applications ? inrush current-limiting _________________________________________________________________________________________________________ typical application typical advanced configuration and power interface (acpi) application
micrel, inc. mic2544/2548 april 2010 2 m9999-043010 ordering information* part number enable latch* temperature range package pb-free mic2544-1bm active high -40 c to +85 c 8-pin soic mic2544-1bmm active high -40 c to +85 c 8-pin msop mic2544-2bm active low -40 c to +85 c 8-pin soic mic2544-2bm active low -40 c to +85 c 8-pin msop mic2544-1ym active high -40 c to +85 c 8-pin soic ? mic2544-1ymm active high -40 c to +85 c 8-pin msop ? mic2544-2ym active low -40 c to +85 c 8-pin soic ? mic2544-2ymm active low -40 c to +85 c 8-pin msop ? mic2548-1bm active high ? -40 c to +85 c 8-pin soic mic2548-1bmm active high ? -40 c to +85 c 8-pin msop mic2548-2bm active low ? -40 c to +85 c 8-pin soic mic2548-2bmm active low ? -40 c to +85 c 8-pin msop mic2548-1ym active high ? -40 c to +85 c 8-pin soic ? MIC2548-1YMM active high ? -40 c to +85 c 8-pin msop ? mic2548-2ym active low ? -40 c to +85 c 8-pin soic ? mic2548-2ymm active low ? -40 c to +85 c 8-pin msop ? *thermal shutdown latch
micrel, inc. mic2544/2548 april 2010 3 m9999-043010 pin configuration 8-pin soic (m) 8-pin msop (mm) note: pins 4 and 5 for soic and msop are different. pin description pin number msop-8 pin number soic-9 pin name pin function 1 1 en enable (input): logic-compatible enable input. active-high (-1) or active- low (-2). high input >1.7v typical; low input <1.5v typical. do not float. mic2548 only: also resets thermal shutdown latch. 2 2 flg fault flag (output): active-low, open- drain output. indicates overcurrent or thermal shutdown conditions. mic2548 only: latched low on thermal shutdown. 3 3 gnd ground. 5 4 ilim current limit: sets current-limit thre shold using an external resistor, r set 1 connected to ground. 154 < r set < 2.29k . 7 7 in input: output mosfet drain. also powers internal circuitry. 6,8 6,8 out switch (output): output mosfet source. pins 6 and 8 must be externally connected. 4 5 nc not internally connected.
micrel, inc. mic2544/2548 april 2010 4 m9999-043010 absolute maximum ratings (1) supply voltage (v in ) ....................................................+7.0v output voltage (v out ) .................................................+7.0v output current (i out ) .................................internally limited enable input (v en ) .................................. ?0.3v to vin+0.3v fault flag voltage (v flg ).............................................+7.0v fault flag current (i flg ) ..............................................50ma storage temperature (t s ) .........................?65c to +150 c junction temperature (t j ) ........................internally limited lead temperature (solde ring, 5 se c.)........................ 260c esd rating (3) .................................................................. 2kv operating ratings (2) supply voltage (v in )..................................... +2.7v to +5.5v current limit set rang e................................... 0.1a to 1.5a ambient temperature (t a ) .......................... ?40c to +85c package thermal resistance soic ( ja ) ........................................................160c/w msop ( ja ) ......................................................206c/w electrical characteristics v in = +5v; t a = 25c, bold values indicate ?40c to +85c, unless noted. symbol parameter condition min typ max units switch off, out = open (4) # 0.75 5 a supply current switch on, out = open (4) 75 160 a enable high (4) 2.4 1.7 v v en enable input voltage enable low (1) 1.5 0.8 v enable input capacitance note 5 1 pf r ds(on) switch resistance i out = 500ma 80 120 m i out = 100ma to 1a, v out =1v to 4v (6) 184 230 276 v current limit factor i out = 500ma to 1.5a, v out =1v to 4v (6) 161 230 299 v output leakage current switch off 1 10 a t on output turn-on delay r l = 10 , c l = 1 f, figures 1a, 1b 1 2 5 ms t r output turn-on rise time r l = 10 , c l = 1 f, figures 1a, 1b 1 2 5 ms t off output turn-off delay r l = 10 , c l = 1 f, figures 1a, 1b 22 s t f output turn-off fall time r l = 10 , c l = 1 f, figures 1a, 1b 21 s t j increasing 140 c overtemperature threshold shutdown t j decreasing 130 c v in = 5v, i l = 10 a 4 15 error flag output resistance v in = 3.3v, i l = 10 a 5 20 error flag off current v flg = 5v 0.01 1 a en pulse reset width mic2548 thermal shutdown latch 5 s v in to en set-up mic2548 (6) 0 s current-limit response time v out = 0v (6) 25 s overcurrent flag response time v out = v in /2 to flg low 5 s notes: 1. exceeding the absolute maximum rating may damage the device. 2. the device is not guaranteed to function outside its operating rating. 3. devices are esd sensitive. handli ng precautions recommended. human body mo del, 1.5k in series with 100pf. 4. off is 0.8v and on is 2.4v for the mic2544-1 and mic2548-1. off is 2.4v and on is 0.8v for the mic2544-2 and mic2548-2. the enable input has about 200mv of hysteresis. 5. guaranteed by design but not production tested. 6. current limit threshold is determined by i limit = , where r set is in ohms. 230v r set
micrel, inc. mic2544/2548 april 2010 5 m9999-043010 test circuit functional characteristics test circuit timing diagrams figure 1a. mic2544/48-1 figure 1b. mic2544/48-2
micrel, inc. mic2544/2548 april 2010 6 m9999-043010 timing diagrams continued figure 2a. mic2548-2 timing: out put is reset by toggling en figure 2b. mic2544-2 timing
micrel, inc. mic2544/2548 april 2010 7 m9999-043010 typical characteristics
micrel, inc. mic2544/2548 april 2010 8 m9999-043010 typical characteristics continued
micrel, inc. mic2544/2548 april 2010 9 m9999-043010 functional characteristics
micrel, inc. mic2544/2548 april 2010 10 m9999-043010 block diagram
micrel, inc. mic2544/2548 april 2010 11 m9999-043010 functional description the mic2544 and mic2548 are high-side n-channel switches available with active-high or active-low enable inputs. fault conditions turn-off or inhibit turn-on of the output transistor and activate the open-drain error flag transistor making it sink current to ground. input and output in is the power supply conne ction to the logic circuitry and the drain of the output mosfet. out is the source of the output mosfet. in a typical circuit, current flows from in to out toward the load. if vout is greater than vin, current will flow from ou t to in since the switch is bidirectional when enabled. the output mosfet and driver circuitry are also designed to allow the mosfet source to be externally forced to a higher voltage than the drain (v out > v in ) when the switch is disabled. in this situation, the mic2544/48 avoids undesirable current flow from out to in. both out pins must be connected together. thermal shutdown thermal shutdown shuts off the output mosfet and signals the fault flag if the die temperature exceeds 140c. 10c of hysteresis prevents the switch from turning on until the die temperature drops to 130c. overtemperature detection functions only when the switch is enabled. the mic2548 features an internal latch which causes the part to remain off after thermal shutdown until a reset pulse is provided via the enable pin (pin 1). while in current-limit, the thermal shutdown latch prevents on/off cycling of the output. refer to figures 2a and 2b for timing diagram. the flag remains low until reset. enable input en must be driven logic high or logic low, or be pulled high or low for a clearly defined input. floating the input may cause unpredictable operation. en should not be allowed to go negative with respect to gnd, and v en should be less than or equal to v in . adjustable current-limit the short-circuit current-limit is user-adjustable with an external set resistor. current-limit in the range of 100ma to 1.5a is available with a set point accuracy of better than 20%. the current-limit circuit prevents damage to the output mosfet and external load. the nominal current-limit value is set with an external resistor between ilim and gn d. for a desired current- limit, the value of the external set resistor is given by: where: 154 < r set < 2.29k for example, to set a 1a nominal current-limit, r set is calculated as: current through r set increases with out current. the voltage across r set could be monitored with a high impedance comparator to provide an indication of output current. r set should be between 154 ? 0.5% and 2.29k ? 0.5%. short-circuit protection in the event of a short circui t, the output current will fold back to approximately 80% of the short-circuit current- limit. fault flag flg is an n-channel, open-drain mosfet output. the faultflag is active (low) for current-limit or thermal shutdown conditions. the flag output mosfet is capable of sinking a 10ma load to typically 100mv above ground.
micrel, inc. mic2544/2548 april 2010 12 m9999-043010 application information supply filtering a 0.1 f to 1 f bypass capacitor from in to gnd, located near the mic2544 and mic2548, is strongly recommended to control supply transients. without a bypass capacitor, an output short may cause sufficient ringing on the input (from supply lead inductance) to damage internal control circuitry. input transients must not exceed the absolute maximum supply voltage (v in max = 6v) even for a short duration. figure 3. supply bypassing power dissipation the device's junction temperature depends on several factors such as the load, pcb layout, ambient temperature, and package ty pe. equations that can be used to calculate power dissipation and junction temperature are found below. calculation of power dissipation can be accomplished by the following equation: pd = r ds(on) (i out ) 2 to relate this to junction temperature, the following equation can be used: t j = p d ja + t a where: t j = junction temperature t a = ambient temperature ja = is the thermal resistance of the package transient overcurrent filter the inrush current from the connection of a heavy capacitive load may cause the fault flag to fall for 10 s to 200 s while the switch is in a constant-current mode, charging the capacitance. adding an optional series resistor-capacitor (r set2 ) in parallel with r set , as shown in figure 4, allows the transient current-limit to be set to a different value than steady state. a typical usb hot-plug inrush is 2a to 3a for 10 s to 20 s. if r set is 435 ? (510ma), an r set2 of 88 ? (2.5a) and c set of 1 f (rc = 100 s) allows transient surge of 3a to pass for 100 s without tripping the overcurrent flag (flg). usb power distribution the mic2544 is ideal for meeting usb power distribution requirements. figure 4 depicts a usb host application. rset should be set to a value providing a current-limit >500ma. the accurate current-limit of the mic2544 will reduce power supply current requirement s. also, fast reaction to short circuit faults prevent voltage droop in mobile pc applications. printed circuit board hot-plug the mic2544/48 are ideal inrush current-limiters suitable for hot-plug applications. due to the integrated charge pump, the mic2544/48 presents a high impedance when off and slowly becomes a low impedance as it turns on. this ?softstart? feature effect ively isolates power supplies from highly capacitive loads by reducing inrush current during hot-plug events. figure 5 shows how the mic2544 may be used in a hot-plug application. figure 4. usb host application note : msop package option uses pin 5 for ilim. pin 4 is not connected (nc). bold lines indicate 0.1? wide, 1- oz. copper high-current traces.
micrel, inc. mic2544/2548 april 2010 13 m9999-043010 figure 5. hot plug application
micrel, inc. mic2544/2548 april 2010 14 m9999-043010 package information 8-pin soic (m) 8-pin msop (mm) micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel +1 (408) 944-0800 fax +1 (408) 474-1000 web http://www.micrel.com the information furnished by micrel in this data sheet is belie ved to be accurate and reliable. however, no responsibility is a ssumed by micrel for its use. micrel reserves the right to change circuitry and specifications at any time without notification to the customer. micrel products are not designed or authori zed for use as components in life support app liances, devices or systems where malfu nction of a product can reasonably be expected to result in pers onal injury. life support devices or system s are devices or systems that (a) are in tended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significan t injury to the user. a purchaser?s use or sale of micrel produc ts for use in life support app liances, devices or systems is a purchaser?s own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2004 micrel, incorporated.

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