MIC2544/2548 Programmable Current Limit High-Side Switch General Description Features 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 (microsmall-outline package). • • • • • • • • • • • 2.7V to 5.5V input Adjustable current-limit up to 1.5A Reverse current flow blocking (no “body diode”) 75μA typical on-state supply current 1μA typical off-state supply current 120mΩ 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. • 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 Micrel, Inc. MIC2544/2548 Ordering Information* Part Number Enable Temperature Range Package MIC2544-1BM Active High Latch* -40°C to +85°C 8-pin SOIC Pb-Free 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 April 2010 2 M9999-043010 Micrel, Inc. MIC2544/2548 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 April 2010 Pin Number SOIC-9 Pin Name Pin Function 1 1 EN Enable (Input): Logic-compatible enable input. Active-high (-1) or activelow (-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 threshold using an external resistor, RSET1 connected to ground. 154Ω < RSET < 2.29kΩ. 7 7 IN 6,8 6,8 OUT 4 5 NC Input: Output MOSFET drain. Also powers internal circuitry. Switch (Output): Output MOSFET source. Pins 6 and 8 must be externally connected. Not internally connected. 3 M9999-043010 Micrel, Inc. MIC2544/2548 Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN) ....................................................+7.0V Output Voltage (VOUT) .................................................+7.0V Output Current (IOUT) .................................Internally Limited Enable Input (VEN) .................................. –0.3V to VIN+0.3V Fault Flag Voltage (VFLG).............................................+7.0V Fault Flag Current (IFLG) ..............................................50mA Storage Temperature (Ts) .........................–65°C to +150°C Junction Temperature (TJ) ........................Internally Limited Lead Temperature (soldering, 5 sec.)........................ 260°C ESD Rating(3) .................................................................. 2kV Supply Voltage (VIN)..................................... +2.7V to +5.5V Current Limit Set Range................................... 0.1A to 1.5A Ambient Temperature (TA) .......................... –40°C to +85°C Package Thermal Resistance SOIC (θJA) ........................................................160°C/W MSOP (θJA) ......................................................206°C/W Electrical Characteristics VIN = +5V; TA = 25°C, bold values indicate –40°C to +85°C, unless noted. Symbol Parameter Condition (4) Supply Current VEN Enable Input Voltage Enable Input Capacitance RDS(on) Switch Resistance Current Limit Factor Switch off, OUT = open Min Typ Max Units # 0.75 5 μA 75 160 μA 2.4 1.7 (4) Switch on, OUT = open Enable high(4) (1) Enable low 1.5 Note 5 V 0.8 1 IOUT = 500mA IOUT = 100mA to 1A, VOUT=1V to 4V(6) (6) IOUT = 500mA to 1.5A, VOUT=1V to 4V V pF 80 120 mΩ 184 230 276 V 161 230 299 V 1 10 μA Output Leakage Current Switch off tON Output Turn-On Delay RL = 10Ω, CL = 1μF, Figures 1a, 1b 1 2 5 ms TR Output Turn-On Rise Time RL = 10Ω, CL = 1μF, Figures 1a, 1b 1 2 5 ms TOFF Output Turn-Off Delay RL = 10Ω, CL = 1μF, Figures 1a, 1b 22 μs TF Output Turn-Off Fall Time RL = 10Ω, CL = 1μF, Figures 1a, 1b 21 μs TJ increasing 140 °C TJ decreasing 130 °C Overtemperature Threshold Shutdown Error Flag Output Resistance VIN = 5V, IL = 10μA 4 15 Ω VIN = 3.3V, IL = 10μA 5 20 Ω 0.01 1 μA Error Flag Off Current VFLG = 5V EN Pulse Reset Width MIC2548 thermal shutdown latch (6) μs 5 μs VIN to EN Set-Up MIC2548 Current-Limit Response Time VOUT = 0V(6) 0 25 μs Overcurrent Flag Response Time VOUT = VIN/2 to FLG low 5 μs 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. Handling precautions recommended. Human body model, 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 ILIMIT = 230V , where RSET is in ohms. RSET April 2010 4 M9999-043010 Micrel, Inc. MIC2544/2548 Test Circuit Functional Characteristics Test Circuit Timing Diagrams Figure 1a. MIC2544/48-1 Figure 1b. MIC2544/48-2 April 2010 5 M9999-043010 Micrel, Inc. MIC2544/2548 Timing Diagrams continued Figure 2a. MIC2548-2 Timing: Output is reset by toggling EN Figure 2b. MIC2544-2 Timing April 2010 6 M9999-043010 Micrel, Inc. MIC2544/2548 Typical Characteristics April 2010 7 M9999-043010 Micrel, Inc. MIC2544/2548 Typical Characteristics continued April 2010 8 M9999-043010 Micrel, Inc. MIC2544/2548 Functional Characteristics April 2010 9 M9999-043010 Micrel, Inc. MIC2544/2548 Block Diagram April 2010 10 M9999-043010 Micrel, Inc. MIC2544/2548 Functional Description 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 GND. For a desired currentlimit, the value of the external set resistor is given by: 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 connection 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 OUT 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 (VOUT > VIN) 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. where: 154Ω < RSET <2.29kΩ For example, to set a 1A nominal current-limit, RSET is calculated as: Thermal Shutdown Thermal shutdown shuts off the output MOSFET and signals the fault flag if the die temperature exceeds 140°C. 10°C of hysteresis prevents the switch from turning on until the die temperature drops to 130°C. 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. Current through RSET increases with OUT current. The voltage across RSET could be monitored with a high impedance comparator to provide an indication of output current. RSET should be between 154Ω ±0.5% and 2.29kΩ ±0.5%. Short-Circuit Protection In the event of a short circuit, the output current will fold back to approximately 80% of the short-circuit currentlimit. 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. 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 VEN should be less than or equal to VIN. April 2010 11 M9999-043010 Micrel, Inc. MIC2544/2548 where: Tj = junction temperature TA = ambient temperature θJA = is the thermal resistance of the package Application Information Supply Filtering A 0.1μF to 1μF 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 (VIN max = 6V) even for a short duration. Transient Overcurrent Filter The inrush current from the connection of a heavy capacitive load may cause the fault flag to fall for 10μs to 200μs while the switch is in a constant-current mode, charging the capacitance. Adding an optional series resistor-capacitor (RSET2) in parallel with RSET, 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 10μs to 20μs. If RSET is 435Ω (510mA), an RSET2 of 88Ω (2.5A) and CSET of 1μF (RC = 100μs) allows transient surge of 3A to pass for 100μs 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 requirements. Also, fast reaction to short circuit faults prevent voltage droop in mobile PC applications. 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 type. 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 = RDS(on) × (IOUT)2 To relate this to junction temperature, the following equation can be used: Tj = PD × θJA + TA 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 effectively 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. April 2010 12 M9999-043010 Micrel, Inc. MIC2544/2548 Figure 5. Hot Plug Application April 2010 13 M9999-043010 Micrel, Inc. MIC2544/2548 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 believed to be accurate and reliable. However, no responsibility is assumed 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 authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended 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 significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, 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. April 2010 14 M9999-043010