MIC2012 Micrel MIC2012/MIC2072 USB Power Controller General Description Features The MIC2012 is a dual channel USB power switch designed to support the power distribution requirements for USB Wakeup from the ACPI S3 state. The MIC2012 will directly switch its two outputs between a 5V main supply and a 5V auxiliary supply normally provided in ATX style power supplies. The MIC2012 will adjust its current-limit threshold according to the ACPI state it is in. In the normal active S0 state the current-limit is set at 500mA minimum per channel satisfying the USB continuous output current specification. In the S3 state the current-limit can be reduced to only 100mA per channel to minimize the current that is supplied by the auxiliary supply thereby ensuring that voltage regulation is maintained even during fault conditions. The MIC2012 provides make-before-break switching to ensure glitch-free transitions between the S3 and S0 states. Each channel is also thermally isolated from the other so that a fault in one channel does not effect the other. FAULT status output signals are also provided indicating overcurrent and thermal shutdown conditions. The MIC2072 option latches the output off upon detecting an overcurrent condition for more than 5ms minimum. The output can be reset by either toggling the EN inputs of the MIC2072-1, -2 or by removing the load. Latching the output off provides a circuit breaker mode of operation which reduces power consumption during fault conditions. • • • • • • • • • • • • Compliant to USB power distribution specifications UL Recognized Component Two completely independent switches Integrated switching matrix supports ACPI S0/S3 state transitions without external FET circuits Make-before-break switching ensures glitch-free transitions No back-feed of auxiliary supply onto main supply during standby mode Bi-level current-limit preserves auxiliary supply voltage regulation in standby mode Thermally isolated channels Thermal shutdown protection Fault status outputs with filter prevents false assertions during hot-plug events Latched thermal shutdown options with auto-reset (MIC2072) Undervoltage lockout Applications • • • • • Desktop PCs Notebook PCs Notebook Docking stations LAN Servers PC Motherboards Typical Application ATX Power Supply 5V MAIN VBUS 5V STANDBY D+ MIC2012P MAIN AUX S3 Control D– OUT1 OUT2 Downstream USB Port 1 GND 100F S3# FAULT1# VBUS D+ FAULT2# GND 100F 82801AA or Equivalent D– Downstream USB Port 2 GND SLP S3# SLP S5# OC0 OC1 Overcurrent Port 1 Overcurrent Port 1 Figure 1. USB Wakeup with Control Input UL Recognized Component Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com January 2005 1 MIC2012/2072 MIC2012 Micrel Ordering Information Part Number Enable Fault Output Circuit Breaker Range Temperature Range Package Standard Pb-Free MIC2012BM(1) MIC2012YM(1) n/a Open-Drain 0°C to +70°C 8-lead SOIC MIC2012CM MIC2012ZM n/a Open-Drain 0°C to +70°C 8-lead SOIC MIC2012PCM MIC2012PZM MIC2012-1PCQS MIC2012-1PZQS n/a Internal Pull-Up 0°C to +70°C 8-lead SOIC Active High Internal Pull-Up 0°C to +70°C 16-lead QSOP MIC2012-2PCQS MIC2012-2PZQS Active Low Internal Pull-Up MIC2072-1PCQS MIC2072-2PZQS Active High Internal Pull-Up Δ 0°C to +70°C 16-lead QSOP 0°C to +70°C 16-lead QSOP MIC2072-2PCQS MIC2072-2PZQS Active Low Internal Pull-Up Δ 0°C to +70°C 16-lead QSOP Note: 1. Contact factory for availablity Pin Configuration FAULT1 FAULT1 1 8 FAULT2 S3# 2 7 OUT1 AUX 3 6 MAIN GND 4 5 OUT2 8-Pin SOIC (M) 1 16 FAULT2 EN1 2 15 EN2 S3# 3 14 OUT1 NC 4 13 OUT1 AUX 5 12 MAIN NC 6 11 MAIN NC 7 10 OUT2 GND 8 9 OUT2 16-Pin QSOP (QS) MIC2012/2072 2 January 2005 MIC2012 Micrel Pin Description Pin Number (MIC2012) Pin Number (MIC2012-1, -2) Pin Name 1 1 FAULT1 Fault Status (Output): Internal pull-up or open-drain. Asserted LOW when Channel is in a thermal shutdown state or overcurrent condition for more than 5ms. MIC2072 latches this output in its asserted state upon an overcurrent condition. Toggling EN1 or removing the load will reset the circuit breaker latch and deassert FAULT1. n/a 2 EN1 Enable (Input): Channel 1, active-high (–1) or active-low (–2). Toggling this input also resets the latched output of the MIC2072. 2 3 S3# Control (Input): When this input is HIGH, the MAIN inputs are connected to OUT1 and OUT2 via 100mΩ MOSFET switches. When this input is LOW the AUX inputs are connected to OUT1 and OUT2 via 500mΩ MOSFET switches. 3 5 AUX Auxiliary 5V Supply (Input): Also used as power supply for internal circuitry. n/a 4, 6, 7 NC 4 8 GND Ground 5 9, 10 OUT2 Channel 2 (Output): For MIC2012-1, -2 both pins must be externally connected together. 6 11, 12 MAIN 5V Main Supply (Input): All MAIN inputs must be connected together externally. 7 13, 14 OUT1 Channel 1 (Output): For MIC2012-1, -2 both pins must be externally connected together. n/a 15 EN2 Enable (Input): Channel 2, active-high (–1) or active-low (–2). Toggling this input also resets the latched output of the MIC2072. 8 16 FAULT2 Fault Status (Output): Internal pull-up or open-drain. Asserted LOW when Channel 2 is in a thermal shutdown state or overcurrent condition for more than 5ms. MIC2072 latches this output in its asserted state upon an overcurrent condition. Toggling EN2 or removing the load will reset the circuit breaker latch and deassert FAULT2. January 2005 Pin Function No Connection: This pin may be connected to other pins without restriction. 3 MIC2012/2072 MIC2012 Micrel Absolute Maximum Ratings (Note 1, Note 4) Operating Ratings (Note 2) Supply Voltage (VIN, VMAIN, VAUX) .....................–0.3V to 6V EN1, EN2, S3# Input Pins .................................–0.3V to 6V FAULT#, OUT1, OUT2 Output Pins...................–0.3V to 6V FAULT Output Current ................................................ 25mA ESD Rating, Note 3 ...................................................... 2kV Supply Voltage (VMAIN, VAUX) ...................... +4.5V to +5.5V Ambient Temperature (TA) ............................ –0°C to +70°C Junction Temperature (TJ) ........................ Internally Limited Package Thermal Resistance QSOP (θJA)....................................................................... 163°C/W SOIC (θJA)......................................................................... 160°C/W Electrical Characteristics VMAIN = 5V; AUX = 5V; TA = 25°C; unless noted Symbol Parameter Condition VMAIN MAIN Supply Voltage IMAIN (ON) MAIN Supply Current Switches On Note 5 IMAIN (OFF) MAIN Supply Current Switches Off S3# = 1, no load Note 5, (MIC20x2-1, MIC20x2-2 only) ILEAK MAIN Reverse Leakage Current, VAUX AUX Supply Voltage IAUX ON AUX Supply Current, both switches on, Note 5 No load S3# = 0 IAUX OFF AUX Supply Current, switches off. (MIC20x2-1, MIC20x2-2 only) No load S3# = 0 VUV/AUX AUX Undervoltage Lockout Threshold VAUX increasing VAUX decreasing VHYS AUX Undervoltage Lockout Hysteresis Min Typ Max 4.5 5.0 5.5 V 16 22 µA 5 µA +10 µA 5.0 5.5 V 0.6 1 mA 5 µA 4.0 3.8 V V S3# = 1, no load S3# = 0, both switches ON, VMAIN = 0V –10 4.5 3.1 2.9 200 Units mV RDSMAIN MAIN On-Resistance, Each Output S3# = 1, IOUT = 500mA 100 140 mΩ RDSAUX AUX On-Resistance, Each Output S3# = 0, IOUT = 100mA 500 700 mΩ ILIMIT(MAIN) MAIN Current-Limit Threshold S3# = 1, VOUT = 4.0V, ramped load 0.8 2.0 A MAIN Short-Circuit Current-Limit VOUT = 0V 0.65 1.8 A AUXCurrent-Limit Threshold S3# = 0, VOUT = 4.0V, ramped load 105 195 mA AUX Short-Circuit Current-Limit VOUT = 0V, COUT = 100µF S3#, EN1, EN2. Input Threshold Voltage (EN1, EN2, for MIC20x2-x only) Low-to-High transition ILIMIT(AUX) VTH High-to-Low transition 150 80 0.8 mA 1.5 1.7 V 2.0 V VHYS EN1, EN2 and S3# Input Hysteresis (EN1, EN2, for MIC20x2-x only) IIN S3#, EN1, EN2 Input Current (EN1, EN2, for MIC20x2-x only) VS3/EN = 5V, 0V –1 1 µA IOFF OUT1, OUT2 Leakage Current (MIC2012-x, MIC2072-x only) Outputs are off, VOUT = 0 –10 10 µA Pull-Up Current During Latched Output State (MIC2072-1, -2) Outputs latched off MIC2012/2072 200 4 1 mV mA January 2005 MIC2012 Micrel Symbol Parameter Condition Min VTH LATCH Latch Reset Threshold (MIC2072, MIC2072-x only) VOUT Rising Minimum Output Slew Rate to Reset Latch (MIC2072, MIC2072-x only), Note 6 Overtemperature Threshold TJ increasing, single channel TJ decreasing, single channel TJ increasing, both channels TJ decreasing, both channels VOL FAULT Output Low Voltage IFAULT = 5mA VOH FAULT Output High Voltage (MIC2012-1P,-2P),(MIC2072-1P,-2P) IFAULT = –20µA FAULT Output Off Current (Not Applicable to 'P' Options) VFAULT = 5V Typ Max Units 1.95 V 0.4 V/s 140 120 160 150 °C °C °C °C 0.2 4 V V 0.2 10 µA TH MAIN to S3# Hold Time, Note 6 Figure 5 5 ms TS MAIN to S3# Set-up Time, Note 6 Figure 5 0 ms tDLY FAULT Delay Filter Response Time (Overcurrent only), Note 7 Output shorted to ground, Figure 4 5 tOC Overcurrent Response Time Output shorted to ground, Figure 4 MAIN output AUX output 10 20 ms 2 2 µs µs tON(MAIN) MAIN Output Turn-On Time RL = 10Ω, CL = 1µF, Figure 3 2 ms tOFF(MAIN) MAIN Output Turn-Off Time (MIC20x2-x only) RL = 10Ω, CL = 1µF, Figure 3 35 µs tr(MAIN) MAIN Output Rise Time RL = 10Ω, CL = 1µF, Figure 3 2 ms tf(MAIN) MAIN Output Fall Time (MIC20x2-x only) RL = 10Ω, CL = 1µF, Figure 3 32 µs tON(AUX) AUX Output Turn-On Time RL = 50Ω, CL = 1µF, Figure 3 0.6 ms tOFF(AUX) AUX Output Turn-Off Time (MIC20x2-x only) RL = 50Ω, CL = 1µF, Figure 3 120 µs tr(AUX) AUX Output Rise Time RL = 50Ω, CL = 1µF, Figure 3 0.5 ms tf(AUX) AUX Output Fall Time (MIC20x2-x only) RL = 50Ω, CL = 1µF, Figure 3 115 µs tXMA MAIN to AUX Cross Conduction Time, Note 8 S3# transition to 0 5 7.5 ms tXAM AUX to MAIN Cross Conduction Time, Note 8 S3# transition to 1 5 7.5 ms Note 1. Exceeding the absolute maximum rating may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. Note 4. All voltages are referenced to ground. Note 5. For MIC20x2-1(P) OFF occurs when VEN < 0.8V and ON occurs when VEN > 2.4V. For MIC20x2-2(P) OFF occurs when VEN > 2.4V and ON occurs when VEN < 0.8V. Note 6. Guaranteed by design. Not production tested. Note 7. Assumes only one channel in current-limit. Delay circuitry is shared among channels so it is possible for tDLY to be 40ms max if one channel enters current-limit as the other is about to time-out. Note 8. Cross conduction time is the duration in which both MAIN and AUX internal switches are on subsequent to S3# transitioning. January 2005 5 MIC2012/2072 MIC2012 Micrel Timing Diagrams 50% VE N tO F F tON 90% VOUT 10% Figure 2. MIC2012/72-1 50% VE N tO F F tON 90% VOUT 10% Figure 3. MIC2012/72-2 Output shorted to ground VOUT IOUT ILIMIT tOC FAULT# tDLY Figure 4. Overcurrent Response Timing tH tS MAIN S3# 1.5V 1.5V Figure 5. MAIN to S3# Timing MIC2012/2072 6 January 2005 MIC2012 Micrel Test Circuit VOUT Device Under OUT Test IOUT RL CL tr tf 90% VOUT 10% 10% January 2005 90% 7 MIC2012/2072 MIC2012 Micrel Typical Characteristics Main Supply Current vs. Temperature Main Supply Current vs. Temperature (Main 1 and Main 2 = ON) V MAIN = 4.5, 5.0, 5.5V EN1 = EN2 = [ON],V 25 AUX = S3# = 5.0V 0.25 0.225 15 5.0 V MAIN 4.5 V MAIN 10 5 0.05 IOUT = 0µA 0 20 40 60 TEMPERATURE (°C) 80 100 Main Short-Circuit Current-Limit Threshold vs. Temperature 1.40 1.35 V MAIN = 5.0V = S3# = 4.5, 5.0, 5.5V V EN1 = EN2 = [OFF],V 5.0V AUX 4.5V AUX 5.5V AUX 0.025 0 -40 -20 IOUT = 0µA 0 20 40 60 TEMPERATURE (°C) 80 100 0 20 40 60 TEMPERATURE (°C) 80 100 1.05 4.5V AUX 1.00 -40 -20 Main Rise-Time vs. Temperature 2000 (AUX 1 and AUX 2 = ON) V AUX = S3# = 4.5, 5.0, 5.5V 4.5V AUX V AUX = 4.5, 5.0, 5.5V 900 V = S3# = 0V MAIN 800 600 1000 500 800 400 5.5 V AUX R L = 10Ω C L = 1µF 200 -40 -20 0 20 40 60 TEMPERATURE (°C) 80 100 100 -40 -20 Enable Threshold (decreasing) vs. Temperature (MIC2012-1/-2) 5.5V AUX 2.0 1.8 1.6 80 100 Enable Threshold (increasing) vs. Temperature (MIC2012-1/-2) 2.2 5.5V AUX 1.4 4.5 V AUX 1.4 1.2 -40 -20 0 20 40 60 TEMPERATURE (°C) 5.0 V AUX 80 100 5.0V MAIN 1.0 -40 -20 Enable Threshold (decreasing) vs. Temperature ( MIC2012-1/-2) 1.8 5.5V MAIN 4.5 V AUX 1.2 V AUX = 4.5, 5.0, 5.5V V MAIN = S3# = 5.0V 80 100 (Output Latched Off–MIC2072) 1600 4.5V MAIN 0 20 40 60 TEMPERATURE (°C) Pull-Up Current vs. Temperature 1800 2.0 2.0 V AUX = 4.5, 5.0, 5.5V V MAIN = S3# = 5.0V 1.6 5.0 V AUX 4.5 V AUX 80 100 2.0 1.8 4.5V MAIN 0 20 40 60 TEMPERATURE (°C) (MIC2012-1/-2) 2.2 0.20 5.0 V AUX 0.10 0.00 -40 -20 0 20 40 60 TEMPERATURE (°C) IOUT = 0µA EN1 = EN2 = [ON] 200 V AUX = 4.5, 5.0, 5.5V 5.5V AUX 5.0 V AUX 4.5 V AUX 300 Enable Threshold (increasing) vs. Temperature I OUT = 0µA EN1 = EN2 = [OFF] 5.5V AUX 700 5.0 V AUX (AUX 1 and AUX 2 = OFF) V MAIN = S3# = 0V 80 100 1000 V MAIN = 5.0V AUX Supply Current vs. Temperature 0.50 0.40 0.30 0 20 40 60 TEMPERATURE (°C) AUX Supply Current vs. Temperature (EN Toggled) 400 1.10 -40 -20 5.0V AUX 4.5 V MAIN 600 1.15 1.20 1.10 1200 1.20 AUX 1.25 1.15 1400 5.5V AUX 1.25 1.8 5.0 V MAIN 1600 1.30 1.00 0.90 0.80 0.70 0.60 = S3# = 5.0V AUX 5.5V MAIN 1800 AUX V MAIN = 5.0V = S3# = 4.5, 5.0, 5.5V V V MAIN = 4.5, 5.0, 5.5V 0.15 0.125 0.1 0.075 0 -40 -20 1.30 0.2 0.175 5.5V MAIN 20 Main Short-Circuit Current-Limit vs. Temperature (Main 1 and Main 2 = OFF) 30 V MAIN = 5.0 V V AUX = S3# = 4.5, 5.0, 5.5V 1400 1.6 5.5V AUX 1200 5.0V MAIN 1000 1.6 1.4 1.4 V MAIN = 4.5V to 5.5V V AUX = S3# = 5.0V 1.2 1.2 -40 -20 MIC2012/2072 0 20 40 60 TEMPERATURE (°C) 80 100 800 5.5V MAIN 600 V MAIN = 4.5V to 5.5V V AUX = S3# = 5.0V 1.0 -40 -20 0 20 40 60 TEMPERATURE (°C) 8 5.0V AUX 4.5V AUX 400 80 100 200 -40 -20 0 20 40 60 TEMPERATURE (°C) 80 100 January 2005 MIC2012 Micrel Output Reset Threshold vs. Temperature 3.00 2.75 (Output Latched Off –MIC2072) V OUT Rising V V 2.50 MAIN AUX = 5.0 V = S3# = 4.5, 5.0, 5.5V 5.5V AUX 2.25 2.00 1.75 1.50 -40 -20 January 2005 4.5V AUX 5.0V AUX 0 20 40 60 TEMPERATURE (°C) 80 100 9 MIC2012/2072 MIC2012 Micrel Functional Characteristics VOUT FAULT VAUX (2V/div) (2V/div) (2V/div) AUX Shutdown by UVLO IOUT (50mA/div) VAUX ramps from 0V to 5V V VMAIN = S3# = V= 0V = 5V ENMAIN = [ON] AUX RLOAD = 50CL = 100F CLOAD = 1F RL = 10 VMAIN = VAUX = 5V CL = 100F RL = 10 Main Start-up by UVLO Main Shut-down by UVLO IOUT VOUT FAULT VMAIN (200mA/div) (2V/div) (2V/div) (2V/div) 2.96V S3# = 5V EN = [ON] RLOAD = 10½ CLOAD = 1µF VMAIN = VAUX;VMAIN & VAUX ramp from 5V to 0V TIME (500s/div) TIME (10ms/div) Main Turn-On Response Main Turn-Off Response FAULT EN (5V/div) (5V/div) VOUT (5V/div) VOUT (2V/div) VMAIN = VAUX =5V S3# = 5V EN toggles from [OFF] to [ON] RLOAD = 10 CLOAD = 1F IOUT (200mA/div) IOUT (200mA/div) VAUX ramps from 5V to 0V VMAIN = S3# = 0V EN = [ON] RLOAD = 50 CLOAD = 1F TIME (10ms/div) VMAIN = VAUX;VMAIN & VAUX ramp from 0V to 5V S3# = 5V EN = [ON] RLOAD = 10 3.20V CLOAD = 1F TIME (250s/div) MIC2012/2072 2.96V TIME (500s/div) FAULT EN (5V/div) (5V/div) IOUT VOUT FAULT VMAIN (200mA/div) (2V/div)(2V/div) (2V/div) IOUT VOUT FAULT VAUX (50mA/div) (2V/div) (2V/div) (2V/div) AUX Start-up by UVLO VMAIN = VAUX =5V S3# = 5V EN toggles from [ON] to [OFF] RLOAD = 10 CLOAD = 1F TIME (100s/div) 10 January 2005 MIC2012 Micrel FAULT EN (5V/div) (5V/div) AUX Turn-Off Response IOUT (50mA/div) VAUX =5V VMAIN = S3# = 0V EN toggles from [OFF] to [ON] RLOAD = 50 CLOAD = 1F IOUT (50mA/div) VAUX =5V VMAIN = S3# = 0V EN toggles from [ON] to [OFF] RLOAD = 50 CLOAD = 1F VOUT (5V/div) VOUT FAULT EN (5V/div) (5V/div) (5V/div) AUX Turn-On Response TIME (100s/div) Turn-On from S3# to AUX Turn-Off from AUX to S3# VOUT (2V/div) FAULT S3# (5V/div) (5V/div) VOUT FAULT S3# (5V/div) (5V/div) (5V/div) TIME (100s/div) IOUT (50mA/div) IOUT (50mA/div) VAUX =5V, VMAIN = 0V EN = [ON] S3# toggles from [HI] to [LOW] RLOAD = 50 CLOAD = 1F VAUX =5V, VMAIN = 0V S3# toggles from [LO] to [HI] EN = [ON] RLOAD = 50 CLOAD = 1F TIME (1ms/div) Main Inrush Current into CLOAD Main-Ramped to Short by MOSFET FAULT (5V/div) VOUT FAULT EN (5V/div) (5V/div) (5V/div) TIME (100s/div) VOUT (2V/div) VMAIN = VAUX = 5V S3# = 5V EN toggles from [OFF] to [ON] RLOAD = OPEN CLOAD = 10F, 100F, 560F 1.4A IOUT (500mA/div) IOUT (500mA/div) CL = 560F CL = 100F CL = 10F TIME (500s/div) January 2005 VMAIN = VAUX =5V S3# = 5V, EN = [ON] CLOAD = 1F RLOAD toggles from > 1k to <0.5 TIME (50ms/div) 11 MIC2012/2072 MIC2012 Micrel Main Turn-On into Short VOUT FAULT EN (5V/div) (5V/div) (5V/div) FAULT (5V/div) AUX Ramped to Short by MOSFET VOUT (2V/div) VAUX = 5V VMAIN = S3# = 0V, EN = [ON] RLOAD toggles from >1k to <0.5 CLOAD = 1F VMAIN = VAUX =5V S3# = 5V EN toggles from [OFF] to [ON] RLOAD = Short CLOAD = 1F TIME (25ms/div) TIME (2.5ms/div) AUX Turn-On into Short AUX Inrush Current into Large CLOAD VOUT FAULT EN (5V/div) (10V/div) (5V/div) VOUT FAULT EN (2V/div) (5V/div) (5V/div) IIN (500mA/div) IOUT (100mA/div) 1.2A 230mA VAUX =5V VMAIN = S3#= 0V EN toggles from [OFF] to [ON] ILOAD < 10mA CLOAD = 220F IIN (50mA/div) IOUT (100mA/div) VAUX =5V VMAIN = S3# = 0V EN toggles from [OFF] to [ON] CLOAD = 100F AUX Inrush Current into Small CLOAD Main-to-AUX Cross Conduction S3# VOUT (5V/div) (5V/div) TIME (2.5ms/div) VAUX =5V VMAIN = S3# = 0V EN toggles from [OFF] to [ON] ILOAD < 10mA CLOAD = 10F IAUX (50mA/div) IMAIN (50mA/div) TIME (250s/div) TIME (100s/div) MIC2012/2072 VMAIN = VAUX = 5V S3# toggles from [HI] to [LO] EN = [ON] RLOAD = 50 950s C = 1F LOAD IIN (50mA/div) VOUT FAULT EN (5V/div) (10V/div) (5V/div) TIME (2.5ms/div) 12 January 2005 MIC2012 Micrel VMAIN = VAUX =5V S3# toggles from [LO] to [HI] EN = [ON] RLOAD = 50 CLOAD = 1F 3.96ms IMAIN (50mA/div) IAUX (50mA/div) VOUT (5V/div) S3# (5V/div) AUX-to-Main Cross Conduction TIME (1ms/div) January 2005 13 MIC2012/2072 MIC2012 Micrel Functional Diagram MAIN Current Limit MAIN FET Charge Pump + Gate Control EN OUT AUX FET AUX S3# Current Limit Thermal Sense AUX * 'P' options only Latch 10ms Timer * /FAULT *MIC2070-1/2 Only To Other Channel Functional Description The MIC2012/2072 are designed to support the power distribution requirements for USB wakeup from the ACPI S3 state. It integrates two independent channels under control of input S3#. When S3# is asserted LOW (S3 state) the MIC2012/2072 will switch a 500mΩ, 100mA MOSFET switch from the AUX input to each of its two outputs. Conversely when the S3# input is HIGH (S0 state) the MIC2012/72 will switch a 100mΩ, 500mA MOSFET switch from the MAIN input to each of its two outputs. The lower current limit during the ACPI S3 state helps to ensure that the standby supply maintains regulation even during fault conditions. Thermal Shutdown Thermal shutdown is employed to protect the device from damage should the die temperature exceed safe margins due mainly to short circuit faults. Thermal shutdown shuts off the output MOSFET and asserts the FAULT output if the die temperature reaches 140°C and the overheated channel is in current limit. The other channel is not affected. If, however, the die temperature exceeds 160°C, both channels will be shut off even if neither channel is in current limit. Power Dissipation The device’s junction temperature depends on several factors such as the load, PCB layout, ambient temperature and package type. The power dissipated in each channel is PD = RDS(on) × IOUT2 where RDS(on) is the on-resistance of the internal MOSFETs and IOUT is the continuous output current. Total power dissipation of the device will be the summation of PD for both channels. To relate this to junction temperature, the following equation can be used: MIC2012/2072 14 TJ = PD × θJA + TA where: TJ = junction temperature TA = ambient temperature θJA = is the thermal resistance of the package Current Sensing and Limiting The current-limit thresholds are preset internally for each state. The preset level prevents damage to the device and external load but still allows a minimum current of 100mA or 500mA to be delivered to the load depending on the state of the device according to the S3# input. When S3# is LOW the current-limit is set at 100mA minimum. When S3# is HIGH the current-limit is set at 500mA minimum. Should an over-current condition last longer than tDLY, the MIC2072 will latch the faulty output off. The output will remain off until either the load is removed or the EN signal (MIC20721, -2) is toggled. When the MIC2072 enters a latched output condition a 1mA pull-up current source is activated. This provides a way to automatically reset the output once the load is removed without the need to toggle the enable input such as in the MIC2072. Please refer to Figure 7 for timing details. The MIC2012 will automatically reset its output when the die temperature cools down to 120°C. The MIC2012 output and FAULT signal will continue to cycle on and off until the device is disabled or the fault is removed. Figure 6 depicts typical timing. Depending on PCB layout, package, ambient temperature, etc., it may take several hundred milliseconds from the incidence of the fault to the output MOSFET being shut off. This time duration will be shortest in the case of a January 2005 MIC2012 Micrel dead short on the output. exceeds the current-limit threshold. The FAULT response delay time tDLY is typically 10ms. Fault Status Output The FAULT signal is an active-low output with an open-drain or weak pull-up configuration. FAULT is asserted (active-low) when either an overcurrent or thermal shutdown condition occurs. In the case of an overcurrent condition, FAULT will be asserted only after the flag response delay time, tDLY, has elapsed. This ensures that FAULT is asserted only upon valid overcurrent conditions and that erroneous error reporting is eliminated. For example, false overcurrent conditions can occur during hot-plug events when a highly capacitive load is connected and causes a high transient inrush current that Undervoltage Lockout Undervoltage lockout (UVLO) prevents the output MOSFET from turning on until the AUX input exceeds approximately 3.5V. UVLO ensures that the output MOSFETs remain off to prevent high transient inrush current due to stray or bulk load capacitance. This helps to ensure that the power supply Overcurrent Fault EN (MIC2010-2) VOUT FAULT Thermal Shutdown Reached Figure 6. MIC2012 System Timing Overcurrent Fault EN (MIC2070-2) VOUT FAULT Load Removed– Output Reset Figure 7. MIC2072 System Timing— Output Resets When Load is Removed January 2005 15 MIC2012/2072 MIC2012 Micrel Package Information 16-Pin QSOP (QS) 8-Pin SOIC (M) 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 This 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 MIC2012/2072 16 January 2005