mic2505/2506 micrel 6-4 jul 1997 mic2505/2506 single 2a / dual 1a / high-side switches general description the mic2505 and mic2506 are single and dual integrated high-side power switches that consist of ttl compatible inputs, a charge pump, and protected n-channel mosfets. the mic2505/6 can be used instead of separate high-side drivers and mosfets in many low-voltage applications. the mic2505 switches voltages ranging from 2.7v to 7.5v and can deliver at least 2a continuous current. an mic2506 can deliver at least 1a continuous current from each output. a slow turn on feature prevents high inrush current when switching capacitive loads. the internal control circuitry is powered from the same 2.7v to 7.5v. an mic2505/6 output can be forced higher than the input voltage safely while in the off mode. multipurpose open-drain fault flag outputs indicate overcur- rent limiting, open-load detection, thermal shutdown, or un- dervoltage lockout for each channel. overcurrent limiting is internally fixed and requires no exter- nal components. open-load detection is active when the switch is off. when off, a normal load pulls the output pin low. if the load is open, an optional, external, high-value resistor pulls the output pin high, triggering the fault flag. thermal shutdown turns off the output if the die temperature exceeds approximately 135 c. the switch automatically restarts when the temperature falls 10 c. undervoltage lockout (uvlo) shuts off the output if the supply drops below 2.3v typical and reenables the output when the supply exceeds 2.5v typical. the mic2505/6 is available in the 8-pin soic and dip packages with a temperature range of C40 c to +85 c. typical applications load a on off mic2505bm load ctl out flg gnd out gate in optional output delay capacitor 100k in fault 2.7v to 7.5v pull-up resistor (100k) 18 27 36 45 optional open load detect resistor 0.1? a on a off mic2506bm ctl a out a flg a flg b gnd ctl b out b in fault a 2.7v to 7.5v pull-up resistors (100k each) 18 27 36 45 optional open load detect resistors 0.1? load b 100k 100k b on b off fault b single and dual switch/circuit breakers with open-load detection and fault output features ? low mosfet on resistance to 2.7v 30m w typical at 5v (mic2505) 35m w typical at 3.3v (mic2505) 75m w typical at 5v (each mic2506 output) 80m w typical at 3.3v (each mic2506 output) ? 2.7v to 7.5v input ? 110 m a typical on-state supply current ?1 m a typical off-state supply current ? output can be forced higher than input (off-state) ? current limit ? thermal shutdown ? 2.5v undervoltage lockout (uvlo) ? open-load detection ? open-drain fault flag ? 5ms (slow) turn-on and fast turnoff applications ? 3.3v and 5v power management ? pc card card inrush limiting switch ? hot plug-in power supplies ? battery-charger circuits ordering information part number temperature range package single switch mic2505bm C40 c to +85 c 8-pin soic mic2505bn C40 c to +85 c 8-pin dip dual switch mic2506bm C40 c to +85 c 8-pin soic mic2506bn C40 c to +85 c 8-pin dip
jul 1997 6-5 mic2505/2506 micrel 6 pin configuration 1 2 3 4 8 7 6 5 out in out in ctl flg gnd gate mic2505 1 2 3 4 8 7 6 5 out a in gnd out b ctl a flg a flg b ctl b mic2506 pin description pin number pin number pin name pin function mic2505 mic2506 1 1 / 4 ctl (a/b) control (input): noninverting ttl compatible control input. high (> 1.8v typical) = on, low (< 1.6v typical) = off. 2 2 / 3 flg (a/b) fault flag (output): active-low, open-drain output. if ctl is low, indicates open load. if ctl is high, indicates current limit, thermal shutdown, or uvlo. 3 6 gnd ground: return. 4 gate output mosfet gate: open for fastest rise and fall times. connect capacitor to ground to slow rise and fall times. 5, 7 7 in supply input: output mosfet drain. also supplies ics internal circuitry. connect to supply. mic2505 only: pins 5 and 7 must be externally connected. 6, 8 8 / 5 out (a/b) switch output: output mosfet source. typically connect to switched side of load. output voltage can be pulled above input voltage in off mode. mic2505 only: pins 6 and 8 must be externally connected. 8-pin soic (m) 8-pin dip (n) 8-pin soic (m) 8-pin dip (n) logic, charge pump 6, 8 (out) 3 (gnd) (ctl a) 1 (flg a) 2 5, 7 (in) (gate a) 4 mic2505 logic, charge pump logic, charge pump 8 (out a) 5 (out b) 7 (in) 6 (gnd) (ctl a) 1 (flg a) 2 (flg b) 3 (ctl b) 4 mic2506 absolute maximum ratings supply voltage (v in ) .................................................... 8.0v fault flag voltage (v flg ) ............................................. 7.5v fault flag current (i flg ) ............................................ 50ma output voltage (v out ) ................................................. 7.5v output current (i out ) ............................... internally limited gate voltage (v gate ) ......................................... v in + 15v control input (v ctl ) ....................................... C0.3v to 15v storage temperature (t a ) ....................... C65 c to +150 c lead temperature (soldering 5 sec.) ....................... 260 c operating ratings supply voltage (v in ) ................................... +2.7v to +7.5v ambient operating temperature (t a ) ........ C40 c to +85 c thermal resistance soic (q ja ) ......................................................... 160 c/w dip (q ja ) ............................................................ 160 c/w
mic2505/2506 micrel 6-6 jul 1997 electrical characteristics v in = +5v; gate = open; t a = 25 c, bold indicates C40 c t a +85 c; unless noted parameter condition min typ max units supply current mic2505 v ctl = logic 0, out = open .75 5 m a v ctl = logic 1, out = open 110 160 m a mic2506 v ctl = logic 0, out = open .75 5 m a v ctl = logic 1, out = open 110 160 m a control input voltage v ctl = logic 0 ? logic 1 transition 2.1 2.4 v v ctl = logic 1 ? logic 0 transition 0.8 1.9 v control input current v ctl = logic 0 0.01 1 m a v ctl = logic 1 0.01 1 m a control input capacitance 1pf output mosfet resistance mic2505 v in = 5v, t a = 25 c30 50 m w v in = 5v, C40 c < t a < +85 c 60 m w v in = 3.3v, t a = 25 c35 60 m w v in = 3.3v, C40 c < t a < +85 c 75 m w mic2506 v in = 5v, t a = 25 c75 125 m w v in = 5v, C40 c < t a < +85 c 150 m w v in = 3.3v, t a = 25 c80 135 m w v in = 3.3v, C40 c < t a < +85 c 165 m w output turn-on delay mic2505 r l = 10 w 200 850 2000 m s mic2506 r l = 10 w each output 100 700 2000 m s output turn-on rise time mic2505 r l = 10 w 500 3000 7500 m s mic2506 r l = 10 w each output 200 2000 6000 m s output turn-off delay mic2505 r l = 10 w 0.7 20 m s mic2506 r l = 10 w each output 0.8 20 m s output turn-off fall time mic2505 r l = 10 w 1.5 20 m s mic2506 r l = 10 w each output 0.7 20 m s output leakage current 10 m a current limit threshold mic2505 2 4a mic2506 1 23a open load threshold v ctl = logic low, note 1 0.5 1 1.5 v overtemperature shutdown t j increasing 135 c threshold t j decreasing 125 c error flag output resistance v in = 5v, i l = 10ma 10 25 w v in = 3.3v, i l = 10ma 15 40 w error flag off current v flag = 5v 0.01 1 m a uvlo threshold v in = increasing 2.2 2.5 2.7 v v in = decreasing 2.0 2.3 2.5 v general note: devices are esd protected, however, handling precautions recommended. general note: all limits guaranteed by testing or statistical analysis. note 1: open load threshold is the out voltage where flg becomes active (low). out driven high externally. test circuits mic2506bm ctl a out a flg a gnd ctl b out b in 18 27 36 45 flg b b on b off a on a off +5v 1? 10 w 10 w on off mic2505bm ctl out flg gnd out gate in in +5v 18 27 36 45 1? 10 w v flg 10k w 10k w v flg a v flg b 10k w
jul 1997 6-7 mic2505/2506 micrel 6 typical characteristics note 2 -2 024 time ( m s) -5 0 5 10 control (v) -2 0 2 4 6 -2 024 6 output (v) time (ms) mic2505 turn-on, turn-off characteristics r l = 5 w (i l = 1a) 0 20 40 60 80 100 2345678 output resistance (m w ) supply voltage (v) output on resistance vs. supply voltage mic2505 mic2506 0 20 40 60 80 100 -40 -20 0 20 40 60 80 100 on resistance (m w ) temperature ( c) output on resistance vs. temperature mic2506 mic2505 -1 012 time ( m s) -5 0 5 10 control (v) -2 0 2 4 6 -2 024 6 output (v) time (ms) mic2506 turn-on, turn-off characteristics r l = 5 w (i l = 1a) 1.5 2.0 2.5 3.0 -40 -20 0 20 40 60 80 100 threshold voltage (v) temperature ( c) uvlo threshold voltage vs. temperature in rising in falling 0 100 200 300 400 0.1 1 10 100 error flag voltage (mv) error flag current (ma) error flag voltage vs. error flag current flg = active v dd = 3.3v v dd = 5v 0 20 40 60 80 100 120 140 160 180 200 2345678 supply current ( m a) supply voltage (v) on-state supply current vs. supply voltage 0 0.5 1.0 1.5 2.0 2345678 supply current ( m a) supply voltage (v) off-state supply current vs. supply voltage 1.0 1.5 2.0 2.5 2345 threshold voltage (v) supply voltage (v) control threshold vs. supply voltage ctl rising ctl falling 0 20 40 60 80 100 120 140 160 180 200 -40 -20 0 20 40 60 80 100 supply current ( m a) temperature ( c) on-state supply current vs. temperature 0 0.5 1.0 1.5 2.0 -40 -20 0 20 40 60 80 100 supply current ( m a) temperature ( c) off-state supply current vs. temperature 1 1.5 2.0 2.5 -40 -20 0 20 40 60 80 100 threshold voltage (v) temperature ( c) control threshold vs. temperature ctl rising ctl falling
mic2505/2506 micrel 6-8 jul 1997 block diagrams 1.2v reference thermal shutdown osc. charge pump out uvlo gate control in open load detect flg ctl current limit gate gnd mic2505 block diagram 1.2v reference thermal shutdown charge pump out b uvlo gate control in open load detect ctl a gate control out a open load detect flg b charge pump ctl b osc. flg a current limit current limit gnd mic2506 block diagram
jul 1997 6-9 mic2505/2506 micrel 6 functional description the mic2505/6 is a noninverting high-side switch. a logic- high control input turns on the output transistor, and a logic- low turns off the output transistor. fault conditions turn off or inhibit turn on of the output transistor. control input applying a logic-high input to ctl (control input) activates the oscillator, thermal shutdown, uvlo, 1.2v reference, and gate control circuits. if there are no fault conditions, the output mosfet turns on. reference the 1.2v bandgap reference supplies a regulated voltage to the thermal shutdown and undervoltage lockout circuits. the reference is only active when ctl is high. oscillator/charge pump the oscillator produces an 80khz square wave output which drives the charge pump. the oscillator is disabled when ctl is low or during uvlo. the charge pump is a voltage quintupler (5 ). the charge pump capacitors are self contained. gate control the gate control circuit charges the output mosfet gate from the charge pump output or discharges the mosfet gate to ground as determined by ctl, thermal shutdown, or uvlo (undervoltage lockout). an optional, external capacitor may be connected to the mic2505 gate to lengthen the rise and fall times. this slows the turn on and turn off of the mosfet output switch. input and output in (input) is the supply connection to the logic circuitry and the drain of the output mosfet. out (output) is the source of the output mosfet. in a typical circuit, current flows through the switch from in to out toward the load. 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 ctl is low (switch off). in this situation, the mic2505/6 avoids undesirable drain to body diode current flow by grounding the body when the switch is off. (the conventional method for optimum turn on threshold has the source connected to the body. this would allow a large current to flow when v source > v drain + 0.6v.) mic2505 only duplicate in and out leads are not internally connected and must be connected externally for proper operation. thermal shutdown thermal shutdown shuts off the output mosfet and signals the fault flag if the die temperature exceeds 135 c. 10 c of hysteresis prevents the switch from turning on until the die temperature drops to 125 c. overtemperature detection functions only when the control input is high (output mosfet is on). undervoltage lockout uvlo (undervoltage lockout) prevents the output mosfet from turning on until in (input voltage) exceeds 2.5v typical. after the switch turns on, if the voltage drops below 2.3v typical, uvlo shuts off the output mosfet and signals the fault flag. undervoltage detection functions only when the control input is high (output mosfet is on). overcurrent limit the overcurrent limit is preset internally. the preset level prevents damage to the output mosfet but allows a mini- mum current of 2a through the output mosfet for the mic2505 and 1a for each output mosfet for the mic2506. output current is monitored by sensing the voltage drop across the output mosfet drain metal resistance. overcurrent detection functions only when the control input is high (output mosfet is on). open-load detection open-load detection indicates the absence of an output load by signaling the fault flag. open-load detection is optional and is enabled by connecting a high-value pull-up resistor between in and out. if there is no load, the circuit detects a high out (output) voltage (typically 3 1v) and signals the fault flag. under normal conditions, the low resistance of a typical load pulls out low. open-load detection functions only when the control input is low (output mosfet is off). fault flag flg is an n-channel, open-drain mosfet output. the fault- flag is active (low) for one or more of the following conditions: open load, undervoltage, current limit, or thermal shutdown. the flag output mosfet is capable of sinking a 10ma load to typically 100mv above ground.
mic2505/2506 micrel 6-10 jul 1997 applications information supply filtering a 0.1 m f to 1 m f bypass capacitor from in to gnd, located at the mic2505/6, is strongly recommended to control supply transients. without a bypass capacitor, an output short may cause sufficient ringing on the input (from supply lead induc- tance) to destroy the internal control circuitry. input transients must not exceed the absolute maximum supply voltage (v in max = 7.5v) even for a short duration. on off mic2505bm ctl out flg gnd out gate in in 18 27 36 45 0.1? to 1? 2.7v to 7.5v figure 1. supply bypassing the bypass capacitor may be omitted only if board design precautions are followed, such as using extremely short supply leads or power and ground planes. control input ctl 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. open-load detection refer to typical applications (first page). the optional open-load detection resistor supplies a small current to the load when the mic2505/6 is off. (a 100k resistor will draw 50 m a from a 5v supply.) normally, the load dominates, pulling out low. if the load is absent, the optional resistor pulls out high, activating the fault flag. open-load detection will not function with a pure capacitive load. omit the resistor when open load detection is not required and for the minimum off-state supply current. power bus switch the mic2505/6 features a mosfet switch circuit that pre- vents current from flowing backwards (from out to in) when ctl is low (switch off). in figure 2, when u1 is on and u2 is off, this feature prevents current flow from the load (5v) backward through u2 to the 3.3v supply. (if a discrete mosfet and driver were used, the mosfets internal body diode would short the 5v load to the 3.3v supply.) in a bus switch circuit, flg will be active (low) on any switch that is off, whenever the load voltage is greater than the open load threshold (approximately 1v). logic-high = 5v output logic-low = 3.3v output u1 mic2505bm load ctl out flg gnd out gate in in +5v 18 27 36 45 0.1? u2 mic2505bm ctl out flg gnd out gate in in 18 27 36 45 +3.3v 0.1? figure 2. 5v/3.3v switch concept this circuits function would otherwise require a dual driver, two mosfets, plus two diodes (or a dual driver plus four mosfets). hot plug-in applications the mic2505/6 can be used to protect the socket-side and card-side of a supply circuit from transients caused when a capacitive load is connected to an active supply. the switch presents a high impedance when off, and slowly becomes a low impedance as it turns on. this reduces the inrush current and related voltage drop that result from charging a capacitive load. mic2505bm ctl out flg gnd out gate in in 18 27 36 45 0.1? capacitive load 3.3v power control circuitry gnd card socket figure 3. hot plug-in concept the gate capacitor slows the turn on time even more, reduc- ing the inrush.
|
