MIC2005/2015 Fixed Current Limit Power Distribution Switch General Description Features The MIC2005 and MIC2015 are current limiting, highside power switches, designed for general purpose power distribution and control in PCs, PDAs, printers and other self-powered systems. The MIC2005 and MIC2015's primary functions are current limiting and power switching. They are thermally protected and will shut down should their internal temperature reach unsafe levels, protecting both the device and the load, under high current or fault conditions. Features include fault reporting, with fault blanking to eliminate noise-induced false alarms, output slew rate limiting and under voltage detection. Both devices are fully self-contained, with the current limit value being factory set to one of several convenient levels. * 70m typical on-resistance * 2.5V - 5.5V operating range * Pre-set current limit values: 0.5A, 0.8A and 1.2A The MIC2015 offers a unique new feature: KickstartTM, which allows momentary high current surges to pass unrestricted without sacrificing overall system safety. The MIC2005 and MIC2015 are excellent choices for USB and IEEE 1394 (FireWire) applications or for any system where current limiting and power control are desired. The MIC2005 and MIC2015 are offered in space saving 6 pin SOT-23 and 2mm x 2mm MLF packages. Data sheets and support documentation can be found on Micrel's web site at: www.micrel.com. * KickstartTM * Fault status flag * Fault masking: prevents nuisance alarms on current surges or hot plug events * Thermal Protection * Under voltage lock-out * Adjustable slew rate limited Turn-ON * Low quiescent current Applications * * * * * * * * USB / IEEE 1394 Power Distribution Desktop and Laptop PCs Set top boxes Game consoles PDAs Printers Docking stations Chargers _________________________________________________________________________________________________________ Typical Application MIC2005 MIC2015 VIN VOUT 5V Supply CSLEW GND VBUS D+/D- USB Port ENABLE FAULT/ VBUS USB Controller D+/D- USB Port Figure 1. Typical Application Circuit Kickstart is a trademark of Micrel, Inc MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc. Micrel Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel +1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com August 2005 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 MIC2000 Family Members Part Number Pin Function Enable CSLEW FAULT/ DLM* -- -- -- -- -- Load Discharge -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- Kickstart 2003 2013 2004 2014 2005 2015 2006 2016 -- 2007 2017 2008 2018 2009 2019 * Dynamic Load Management I Limit I Adj. Normal Limiting Fixed Adj. Adj = Adjustable current limit Fixed = Factory programmed current limit Ordering Information Part Number Marking(1) Current Limit MIC2005-0.5YM6 FF05 0.5A MIC2005-0.8YM6 FF08 0.8A MIC2005-1.2YM6 FF12 1.2A MIC2005-0.5YML(2) F05 0.5A MIC2005-0.8YML(2) F08 0.8A (2) F12 1.2A MIC2015-0.5YM6 FN05 0.5A MIC2015-0.8YM6 FN08 0.8A MIC2005-1.2YML MIC2015-1.2YM6 FN12 1.2A (2) N05 0.5A MIC2015-0.8YML(2) N08 0.8A (2) N12 1.2A MIC2015-0.5YML MIC2015-1.2YML Kickstart Pb-Free Package SOT-23-6 No Yes 2mmX2mm MLF SOT-23-6 Yes 2mmX2mm MLF Notes: 1. Under-bar symbol ( _ ) may not be to scale. 2. Contact factory for availability. August 2005 2 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 Pin Configuration VOUT 1 6 VIN PA D O N BACKSIDE IS GROUND CSLEW 2 FAULT/ 5 GND 4 ENABLE 3 VIN 1 6 VOUT GND 2 5 CSLEW ENABLE 3 4 FAULT/ SOT 23-6 (M6) Top View 6-Lead 2mm x 2mm MLF (ML) Top View Pin Description Pin Number SOT-23 Pin Number MLF Pin Name 1 6 VIN Input 2 5 GND -- 3 4 ENABLE Input Output enable pin. A logic HIGH activates the output switch, applying power to the load attached to VOUT. 4 3 FAULT/ Output Fault status. A logic LOW on this pin indicates the MIC2005/2015 is in current limiting, or has been shut down by the thermal protection circuit. This is an `Open Drain' output allowing logical OR'ing of multiple MIC2005/2015s. 5 2 CSLEW Input Slew rate control. Adding a small value capacitor between this pin and VIN slows turn-ON of the power FET. 6 1 VOUT Output Switch output. The load being driven by MIC2005/2015 is connected to this pin. August 2005 Type Description Supply input. This pin provides power to both the output switch and the MIC2005/2015's internal control circuitry. Ground. 3 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 Absolute Maximum Ratings(1) Operating Ratings(2) VIN, VOUT ............................................................ -0.3 to 6V All other pins .................................................. -0.3 to 5.5V Power Dissipation.................................. Internally Limited Continuous Output Current..................................... 2.25A Maximum Junction Temperature ........................... 150C Storage Temperature .............................. -65C to 150C Supply Voltage............................................. 2.5V to 5.5V Continuous Output Current Range .................... 0 to 2.1A Ambient Temperature Range .................... -40C to 85C Package Thermal Resistance (JA) SOT-23-6 ............................................. MLF 2x2 mm............................................ MLF 2x2 mm JC (5) .................................. 230C/W 90C/W 45C/W Electrical Characteristics VIN = 5V, TAMBIENT = 25C unless specified otherwise. Bold indicates -40C to +85C limits. Symbol Parameter VIN Switch Input Voltage IIN Internal Supply Current IIN Internal Supply Current Conditions Min Typ Max Units 5.5 V 1 5 A 80 330 A 12 100 A 70 100 m 125 m 2.5 Switch = OFF, ENABLE = 0V Switch = ON, IOUT = 0 ENABLE = 1.5V ILEAK Output Leakage Current VIN = 5V, VOUT = 0 V, ENABLE = 0 RDS(ON) Power Switch Resistance VIN = 5V, IOUT = 100 mA ILIMIT Current Limit: -0.5 VOUT = 0.8VIN 0.5 0.7 0.9 A ILIMIT Current Limit: -0.8 VOUT = 0.8VIN 0.8 1.1 1.5 A ILIMIT Current Limit: -1.2 VOUT = 0.8VIN 1.2 1.6 2.1 A ILIMIT_2nd Secondary current limit (Kickstart) MIC2015, VIN = 2.5V 2.2 4 6 A UVLOTHRESHOLD Under Voltage Lock Out threshold VIN rising 2.0 2.25 2.5 V VIN falling 1.9 2.15 2.4 V 0.5 V 1 5 A 0.4 V VEN ENABLE Input Voltage VIL(max.) VIH(min.) IEN ENABLE Input Current VFAULT Fault status Output Voltage IOL = 10mA .25 OTTHRESHOLD Over-temperature Threshold TJ increasing 145 TJ decreasing 135 August 2005 VEN = 0V to 5.0V 1.5 4 C M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 AC Characteristics Symbol Parameter Condition Min Typ Max Units tRISE Output turn-ON rise time RL = 10, CLOAD = 1F, 500 1000 1500 s tD_FAULT Delay before asserting or releasing FAULT/ 20 32 49 ms 77 128 192 ms VOUT = 10% to 90% Time from current limiting to FAULT/ state change. MIC2005 Time from Iout continuously exceeding primary current limit condition to FAULT/ state change. MIC2015 tD_LIMIT Delay before current limiting MIC2015 77 128 192 ms tRESET Delay before resetting Kickstart current limit delay, tD_LIMIT Out of current limit following a current limit event. 77 128 192 ms Output Turn-on Delay RL = 43, CL = 120F, 1000 1500 s 700 s Max Units tON_DLY (MIC2015 only) CSLEW 10pF, VEN = 50% to VOUT = 10% tOFF_DLY Output Turn-off Delay RL = 43, CL = 120F, CSLEW 10pF, VEN = 50% to VOUT = 90% ESD Symbol Parameter Condition Min VESD_HB Electro Static Discharge Voltage: Human Body Model VOUT and GND 4 2 kV 200 V VESD_MCHN Electro Static Discharge Voltage; Machine Model All other pins All pins Typ kV Machine Model 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. Specification for packaged product only. 5. Requires proper thermal mounting to achieve this performance. August 2005 5 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 Timing Diagrams ENABLE 50% 50% tON_DLY tOFF_DLY 90% VOUT 10% Switching Delay Times tFALL tRISE 90% 90% 10% 10% Rise and Fall Times tRISE 90% VOUT 10% Output Rise Time August 2005 6 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 Typical Characteristics Supply Current Output Enabled 1.00 25C -40C 80 85C 0.80 0.70 (A) 0.50 0.40 40 -40C 0.30 0.20 20 4 VIN (V) 5 0 2 6 I 1.6 1.60 ILIMIT (A) 0.8A 1.0 0.8 0.5A 0.6 1.45 0.2 1.30 0 -50 -30 -10 10 30 50 70 TEMPERATURE (C) VIN = 5V vs. Temperature (MIC20xx - 0.5) 0.61 5V 0.59 3V 0.57 2.5V 0.55 -50 -30 -10 10 30 50 70 TEMPERATURE (C) 100 0.60 5V 0.20 3V overlay each 2.5V other. 0.00 -50 -30 -10 10 30 50 70 TEMPERATURE (C) RON vs. Temperature 120 100 20 0 2 3.3V 90 2.5V 80 60 5V 40 20 2.5 3 3.5 4 4.5 VIN (V) 5 5.5 0 -50 -30 -10 10 30 50 70 TEMPERATURE (C) 90 UVLO Threshold vs. Temperature 2.25 THRESHOLD (V) the 3 plots RON vs. 40 90 Please note that 0.40 Supply Voltage 60 2.3 V RISING 2.2 V FALLING 2.15 2.1 2.05 -50 August 2005 90 0.80 80 RON (mOhm) 0.75 0.73 0.71 0.69 0.67 0.65 0.63 1.00 RON (mOhm) LIMIT 1.20 1.25 -50 -30 -10 10 30 50 70 TEMPERATURE (C) 90 (MIC20xx - 0.8) 1.40 1.40 1.35 90 ILIMIT vs. Temperature VIN = 3V 1.50 0.4 I 7 VIN = 2.5V 1.55 1.2 6 vs. Temperature (MIC20xx-1.2) 1.65 1.2A 1.4 4 5 VIN (V) LIMIT Temperature 1.8 3 ILIMIT (A) 3 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0 -50 -30 -10 10 30 50 70 TEMPERATURE (C) 25C 85C 0.10 ILIMIT vs. ILIMIT (A) 1.00 0.60 60 0 2 ILIMIT (A) Switch Leakage Current - OFF 0.90 SUPPLY CURRENT (A) SUPPLY CURRENT (A) 100 Supply Current Output Disabled 0 50 100 TEMPERATURE (C) 7 150 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 Functional Characteristics Current Limit Response Thermal Shutdown CSLEW Response FAULT/ (2.5V/div) FAULT/ (2.5V/div) ENABLE (2.5V/div) ENABLE (2.5V/div) 0pF 100pF 1800pF 820pF VIN = 5.0V RLOAD CLOAD = 47F 2700pF 3500pF VOUT (1V/div) VOUT (1V/div) VIN = 5.0V RLOAD CLOAD = 0F IOUT (150mA/div) 0 2000 6000 10000 14000 Time (s) 18000 IOUT (250mA/div) 22000 0 50 100 Kickstart Response Normal Load with Temporary High Load 200 250 300 Time (ms) 350 400 450 500 550 Kickstart Response No Load to Short Circuit FAULT/ (2.5V/div) FAULT/ (1V/div) ENABLE (2.5V/div) ENABLE (1V/div) VOUT (1V/div) VOUT (1V/div) IOUT (0.5A/div) IOUT (0.5A/div) 0 50 100 150 200 250 300 350 Time (ms) 400 450 500 0 550 50 Kickstart Response Normal Load with Temporary Short Circuit FAULT/ (2.5V/div) ENABLE (2.5V/div) ENABLE (2.5V/div) VOUT (1V/div) VOUT (1V/div) IOUT (0.5A/div) IOUT (0.5A/div) 0 50 100 150 200 250 300 350 Time (ms) 400 450 500 100 150 200 250 300 350 Time (ms) 400 450 500 550 Kickstart Response Device Enabled into a Short Circuit FAULT/ (2.5V/div) August 2005 150 0 550 8 50 100 150 200 250 300 350 Time (ms) 400 450 500 550 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 Inrush Current Response MIC20xx-0.5 Turn-On/Turn-Off FAULT/ (2.5V/div) FAULT/ (2.5V/div) RL CSLEW = 0pF ENABLE (2.5V/div) ENABLE (2.5V/div) VIN = 5.0V RLOAD CLOAD = 100F CSLEW = 0pF 0F 10F 22F47F 100F VOUT (1V/div) VOUT (1V/div) 220F 470F IOUT (200mA/div) IOUT (200mA/div) 0 4 8 12 16 20 24 Time (ms) 28 32 36 0 40 2 4 6 UVLO Increasing 8 Time (ms) 10 FAULT/ (2.5V/div) ENABLE (2.5V/div) ENABLE (2.5V/div) Enable tied to VIN Enable tied to V IN VOUT (1V/div) VOUT (1V/div) VIN (1/div) VIN (1/div) August 2005 4 8 12 14 UVLO Decreasing FAULT/ (2.5V/div) 0 12 16 20 24 28 Time (s) 32 36 40 44 0 48 4 8 12 16 20 24 28 32 36 40 44 48 Time (s) 9 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 Functional Diagram Under Voltage Detector VIN Current Mirror FE T Pow er FET ENABLE Control Logic and Delay T imer Gate Control FAULT/ VOUT Thermal Sensor CSLEW Slew Rate Control VREF Curre nt L imit control Loop GND Factory a djuste d Figure 2. MIC2005/2015 Block Diagram August 2005 10 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 immediately to restrict output current to the secondary limit for the duration of the Kickstart period. After this time, the MIC2015 reverts to its normal current limit. An example of Kickstart operation is shown below. Functional Description Input and Output VIN is both the power supply connection for the internal circuitry driving the switch and the input (Source connection) of the power MOSFET switch. VOUT is the Drain connection of the power MOSFET and supplies power to the load. In a typical circuit, current flows from VIN to VOUT toward the load. Since the switch is bidirectional when enabled, if VOUT is greater than VIN, current will flow from VOUT to VIN. When the switch is disabled, current will not flow to the load, except for a small unavoidable leakage current of a few microamps. However, should VOUT exceed VIN by more than a diode drop (~0.6V), while the switch is disabled, current will flow from output to input via the power MOSFET's body diode. This effect can be used to advantage when large bypass capacitors are placed on MIC2005/2015's's output. When power to the switch is removed, the output capacitor will be automatically discharged. If discharging CLOAD is required by your application, consider using MIC2004/2014 or MIC2007/2017 in place of MIC2005/2015. These MIC2000 family members are equipped with a discharge FET to insure complete discharge of CLOAD. OUT OUT Figure 3. Kickstart Operation Picture Key: A) MIC2015 is enabled into an excessive load (slew rate limiting not visible at this time scale) The initial current surge is limited by either the overall circuit resistance and power supply compliance, or the secondary current limit, whichever is less. B) RON of the power FET increases due to internal heating (effect exaggerated for emphasis). C) Kickstart period. D) Current limiting initiated. FAULT/ goes LOW. E) VOUT is non-zero (load is heavy, but not a dead short where VOUT = 0. Limiting response will be the same for dead shorts). F) Thermal shutdown followed by thermal cycling. G) Excessive load released, normal load remains. MIC2015 drops out of current limiting. H) FAULT/ delay period followed by FAULT/ going HIGH. Current Sensing and Limiting The MIC2005/2015 protects the system power supply and load from damage by continuously monitoring current through the on-chip power MOSFET. Load current is monitored by means of a current mirror in parallel with the power MOSFET switch. Current limiting is invoked when the load exceeds an internally set overcurrent threshold. When current limiting is activated, the output current is constrained to the limit value, and remains at this level until either the load/fault is removed, the load's current requirement drops below the limiting value, or the MIC2005/2015 goes into thermal shutdown. Kickstart (MIC2015 only) The MIC2015 is designed to allow momentary current surges (Kickstart) before the onset of current limiting, which permits dynamic loads, such as small disk drives or portable printers to draw the energy needed to overcome inertial loads without sacrificing system safety. In this respect, the MIC2015 differs markedly from MIC2005 and its peers, which immediately limit load current, potentially starving the motor and causing the appliance to stall or stutter. During this delay period, typically 128 ms, a secondary current limit is in effect. If the load demands a current in excess of the secondary limit, MIC2015 acts August 2005 Under Voltage Lock Out Under voltage lock-out insures no anomalous operation occurs before the device's minimum input voltage of 2.5V had been achieved. Prior to reaching this voltage, the output switch (power MOSFET) is OFF and no circuit functions, such as FAULT/ or ENABLE, are considered to be valid or operative. 11 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 surges when charged through a high-side switch such as the MIC2005/2015. For this reason, the MIC2005/2015 provides built-in slew rate control to limit the initial inrush currents upon enabling the power MOSFET switch. Slew rate control is active upon powering up, and upon re-enabling the load. At shutdown, the discharge slew rate is controlled by the external load and output capacitor. On MIC2005/2015 Slew Rate is adjustable and can be further reduced by adding an external capacitance between VIN and the CSLEW pins. Enable ENABLE is a HIGH true control signal, which activates the main MOSFET switch. ENABLE will operate with logic running from supply voltages as low as 1.8V. ENABLE can be wire-OR'd with other MIC2005/2015s or similar devices without damage to the device. ENABLE may be driven higher than VIN, but no higher than 5.5V. FAULT/ FAULT/ is an N-channel `open drain' output, which is asserted (LOW true) when MIC2005/2015's either begins current limiting or enters thermal shutdown. In MIC2005, FAULT/ asserts after a brief delay period, usually 32 ms. This delay ensures that FAULT/ is asserted only upon valid, enduring, over-current conditions and that transitory event error reports are filtered out. MIC2015's FAULT/ asserts at the end of the Kickstart period. This masks initial current surges, such as would be seen by a motor load starting up. If the load current remains above the current limit threshold after the Kickstart has timed out, then FAULT/ will be asserted. After a fault clears, FAULT/ remains asserted for the delay period; 32ms for the MIC2005 or 128 ms for the MIC2015. Because FAULT/ is an `open drain' it must be pulled HIGH with an external resistor output and it may be wire-OR'd with other similar outputs, sharing a single pull-up resistor. FAULT/ may be tied to a pull-up voltage source which is higher than VIN, but no greater than 5.5V. Thermal Shutdown Thermal shutdown is employed to protect the MIC2005/2015 from damage should the die temperature exceed safe operating levels. Thermal shutdown shuts off the output MOSFET and asserts the FAULT/ output if the die temperature reaches 145C. The MIC2005/2015 will automatically resume operation when the die temperature cools down to 135C. If resumed operation results in reheating of the die, another shutdown cycle will occur and the MIC2005/2015 will continue cycling between ON and OFF states until the offending load has been removed. Depending upon PCB layout, package type, ambient temperature, etc., hundreds of milliseconds may elapse from the incidence of a fault to the output MOSFET being shut off. This delay is due to thermal time constants within the system itself. In no event will the device be damaged due to thermal overload because die temperature is monitored continuously by on-chip circuitry. Slew Rate Control Large capacitive loads can create significant current August 2005 12 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 Application Information ILIMIT vs. IOUT measured The MIC2005/2015's current limiting circuitry is designed to act as a constant current source to the load. As the load tries to pull more than the allotted current, VOUT drops and the input to output voltage differential increases. When VIN -VOUT exceeds 1V, IOUT drops below ILIMIT to reduce the drain of fault current on the system's power supply and to limit internal heating of the MIC2005/2015. When measuring IOUT, it is important to bear this voltage dependence in mind, otherwise, the measurement data may appear to indicate a problem when none really exists. This voltage dependence is illustrated in Figures 4 and 5. In Figure 4, output current is measured as VOUT is pulled below VIN, with the test terminating when VOUT is 1V below VIN. Observe that once ILIMIT is reached, IOUT remains constant throughout the remainder of the test. In Figure 5, this test is repeated but with VIN - VOUT exceeding 1V. When VIN - VOUT > 1V, the MIC2005/2015's current limiting circuitry responds by decreasing IOUT, as can be seen in Figure 5. In this demonstration, VOUT is being controlled and IOUT is the measured quantity. In real life applications, VOUT is determined in accordance with Ohm's law by the load and the limiting current. Figure 5. IOUT in Current Limiting for VIN - VOUT >1V NORMALIZED OUTPUT CURRENT (A) This folding back of ILIMIT can be generalized by plotting ILIMIT as a function of VOUT, as shown below. The slope of VOUT between IOUT = 0 and IOUT = ILIMIT (where ILIMIT = 1) is determined by RON of MIC2005/2015 and ILIMIT. 1.2 Normalized Output Current vs. Output Voltage (5V) 1.0 0.8 0.6 0.4 0.2 0 0 1 2 3 4 5 OUTPUT VOLTAGE (V) 6 Figure 6. Figure 4. IOUT in Current Limiting for VIN - VOUT 1V August 2005 13 M9999-080305 (408) 955-1690 MIC2005/MIC2015 NORMALIZED OUTPUT CURRENT (A) Micrel 1.2 from a short circuit fault. For this reason, the upper limit on the value of CSLEW is 4nF. Normalized Output Current vs. Output Voltage (2.5V) Kickstart (MIC2015) Kickstart allows brief current surges to pass to the load before the onset of normal current limiting, which permits dynamic loads to draw bursts of energy without sacrificing system safety. Functionally, Kickstart is a forced override of the normal current limiting function provided by the MIC2015. The Kickstart period is governed by an internal timer which allows current to pass unimpeded to the load for 128ms and then normal (primary) current limiting goes into action. During Kickstart, a secondary current limiting circuit monitors output current to prevent damage to the MIC2015, as a hard short combined with a robust power supply can result in currents of many tens of amperes. This secondary current limit is nominally set at 4 Amps and reacts immediately and independently of the Kickstart period. Once the Kickstart timer has finished its count, the primary current limiting circuit takes over and holds IOUT to its programmed limit for as long as the excessive load persists. Once the MIC2015 drops out of current limiting, the Kickstart timer initiates a lock-out period of 128ms such that no further bursts of current, above the primary current limit, will be allowed until the lock-out period has expired. Kickstart may be over-ridden by the thermal protection circuit and if sufficient internal heating occurs, Kickstart will be terminated and IOUT AE 0. Upon cooling, if the load is still present IOUT AE ILIMIT, not IKICKSTART. 1.0 0.8 0.6 0.4 0.2 0 0 0.5 1.0 1.5 2.0 2.5 OUTPUT VOLTAGE (V) 3.0 Figure 7. CSLEW The CSLEW input is provided to increase control of the output voltage ramp at turn-on. This input allows designers the option of decreasing the output's slew rate (slowing the voltage rise) by adding an external capacitance between the pin, CSLEW, and VIN. This capacitance slows the rate at which the pass FET gate voltage increases and thus, slows both the response to an Enable command as well as VOUT's ascent to its final value. Figure 8 illustrates effect of CSLEW on turn-ON delay and output rise time. Typical Turn-on Times vs. External C Capacitance SLEW 0.014 14 TON 0.012 12 TDELAY TIME (mS) 0.01 10 0.0088 FAULT/ 6 0.006 TRISE 4 0.004 ENABLE 0.002 2 0 0 0.5 4 4.5 3 3.5 2 2.5 0 1 0 1.5 0 0 0 0 0 0 0 V OUT CSLEW (nF) Figure 8. Kickstart CSLEW's effect on ILIMIT An unavoidable consequence of adding CSLEW capacitance is a reduction in the MIC2005/2015's ability to quickly limit current transients or surges. A sufficiently large capacitance can prevent both the primary and secondary current limits from acting in time to prevent damage to the MIC2005/2015 or the system August 2005 Current Limiting IOUT Load Removed 0 14 100 200 300 Time (ms ) 400 500 600 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 any MIC2005/2015 designs intending continuous currents of 1A or more. Figure 9. Kickstart Supply Filtering A 0.1F to 1F bypass capacitor positioned close to the VIN and GND pins of the MIC2005/2015 is both good design practice and required for proper operation of the MIC2005/2015. This will control supply transients and ringing. Without a bypass capacitor, large current surges or an output short may cause sufficient ringing on VIN (from supply lead inductance) to cause erratic operation of the MIC2005/2015's control circuitry. Good quality, low ESR capacitors, such as Panasonic's TE or ECJ series, are suggested. When bypassing with capacitors of 10F and up, it is good practice to place a smaller value capacitor in parallel with the larger to handle the high frequency components of any line transients. Values in the range of 0.01F to 0.1F are recommended. Again, good quality, low ESR capacitors should be chosen. to supply Die Temperature vs. Iout for Tcase = 85C 160 Die Temperature - C 140 120 100 80 60 40 SOT-23 20 MLF 0 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 Iout - Amps Figure 10. Power Dissipation Power dissipation depends upon several factors such as the load, PCB layout, ambient temperature, and supply voltage. Calculation of power dissipation can be accomplished by the following equation: Figure 10 assumes no backside contact is made to the thermal pad provided on the MLF package. For optimal performance at higher current levels, or in higher temperature environments, thermal contact with the PCB and the exposed power paddle on the back side of the MLF package should be made. This significantly reduces the package's thermal resistance thereby extending the MIC2005/2015's operating range. It should be noted that this backside paddle is electrically active and is connected to the MIC2005/2015's GND pin. PD = R DS(ON) x (IOUT )2 To relate this to junction temperature, the following equation can be used: TJ = PD x R (J- A) + TA Where: TJ = junction temperature, 2 Vias 0.3 mm diam. to Ground Plane TA = ambient temperature R(J-A) is the thermal resistance of the package In normal operation, the MIC2005/2015's Ron is low enough that no significant I2R heating occurs. Device heating is most often caused by a short circuit, or very heavy load, when a significant portion of the input supply voltage appears across the MIC2005/2015's power MOSFET. Under these conditions the heat generated will exceed the package and PCB's ability to cool the device and thermal limiting will be invoked. In Figure 10, die temperature is plotted against IOUT assuming a constant case temperature of 85C. The plots also assume a worst case RON of 140 m at a die temperature of 135C. Under these conditions, it is clear that an SOT-23 packaged device will be on the verge of thermal shutdown, typically 145C die temperature, when operating at a load current of 1.25A. For this reason, it is recommend that MLF package be used for August 2005 1.4 mm 0.8 mm Figure 11. Pad for thermal mounting to PCB 15 M9999-080305 (408) 955-1690 Micrel MIC2005/MIC2015 Package Information 6-Pin SOT-23 (M6) 6 Pin 2mmX2mm MLF (ML) 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. (c) 2005 Micrel, Incorporated. August 2005 16 M9999-080305 (408) 955-1690 Micrel August 2005 MIC2005/MIC2015 17 M9999-080305 (408) 955-1690