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MIC2012
Micrel
MIC2012/MIC2072
USB Power Controller
General Description
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.
Features
* * * * * * * * * * * * 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 5V STANDBY MIC2012P MAIN AUX S3 Control S3# FAULT1# FAULT2# GND 100F 82801AA or Equivalent OUT1 OUT2 100F VBUS D+ D- GND Downstream USB Port 1
VBUS D+ D- GND Downstream USB Port 2
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
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MIC2012/2072
MIC2012
Micrel
Part Number
Ordering Information
Standard MIC2012BM(1) MIC2012CM MIC2012PCM MIC2012-1PCQS MIC2012-2PCQS MIC2072-1PCQS MIC2072-2PCQS
Note: 1. Contact factory for availablity
Pb-Free MIC2012YM(1) MIC2012ZM MIC2012PZM MIC2012-1PZQS MIC2012-2PZQS MIC2072-2PZQS MIC2072-2PZQS
Enable n/a n/a n/a Active High Active Low Active High Active Low
Fault Output Open-Drain Open-Drain Internal Pull-Up Internal Pull-Up Internal Pull-Up Internal Pull-Up Internal Pull-Up
Circuit Breaker Range
Temperature Range 0C to +70C 0C to +70C 0C to +70C 0C to +70C 0C to +70C
Package 8-lead SOIC 8-lead SOIC 8-lead SOIC 16-lead QSOP 16-lead QSOP 16-lead QSOP 16-lead QSOP

0C to +70C 0C to +70C
Pin Configuration
FAULT1 1 16 FAULT2 15 EN2 14 OUT1 13 OUT1 12 MAIN 11 MAIN 10 OUT2 9 OUT2
FAULT1
1
8 FAULT2 7 OUT1 6 MAIN 5 OUT2
EN1 2 S3# 3 NC 4 AUX 5 NC 6
S3# 2 AUX 3 GND 4
8-Pin SOIC (M)
NC 7 GND 8
16-Pin QSOP (QS)
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MIC2012
Micrel
Pin Number (MIC2012-1, -2) 1 Pin Name FAULT1 Pin Function 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. Enable (Input): Channel 1, active-high (-1) or active-low (-2). Toggling this input also resets the latched output of the MIC2072. Control (Input): When this input is HIGH, the MAIN inputs are connected to OUT1 and OUT2 via 100m MOSFET switches. When this input is LOW the AUX inputs are connected to OUT1 and OUT2 via 500m MOSFET switches. Auxiliary 5V Supply (Input): Also used as power supply for internal circuitry. No Connection: This pin may be connected to other pins without restriction. Ground Channel 2 (Output): For MIC2012-1, -2 both pins must be externally connected together. 5V Main Supply (Input): All MAIN inputs must be connected together externally. Channel 1 (Output): For MIC2012-1, -2 both pins must be externally connected together. Enable (Input): Channel 2, active-high (-1) or active-low (-2). Toggling this input also resets the latched output of the MIC2072. 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.
Pin Description
Pin Number (MIC2012) 1
n/a 2
2 3
EN1 S3#
3 n/a 4 5 6 7 n/a 8
5 4, 6, 7 8 9, 10 11, 12 13, 14 15 16
AUX NC GND OUT2 MAIN OUT1 EN2 FAULT2
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MIC2012/2072
MIC2012
Micrel
Absolute Maximum Ratings (Note 1, Note 4)
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
Operating Ratings (Note 2)
Supply Voltage (VMAIN, VAUX) ...................... +4.5V to +5.5V Ambient Temperature (TA) ............................ -0C to +70C Junction Temperature (TJ) ........................ Internally Limited Package Thermal Resistance QSOP (JA)....................................................................... 163C/W SOIC (JA)......................................................................... 160C/W
Electrical Characteristics
VMAIN = 5V; AUX = 5V; TA = 25C; unless noted Symbol VMAIN IMAIN (ON) IMAIN (OFF) ILEAK VAUX IAUX ON IAUX OFF VUV/AUX VHYS RDSMAIN RDSAUX ILIMIT(MAIN) ILIMIT(AUX) VTH Parameter MAIN Supply Voltage MAIN Supply Current Switches On Note 5 S3# = 1, no load Condition Min 4.5 Typ 5.0 16 Max 5.5 22 5 -10 4.5 No load S3# = 0 No load S3# = 0 VAUX increasing VAUX decreasing 3.1 2.9 200 S3# = 1, IOUT = 500mA S3# = 0, IOUT = 100mA S3# = 1, VOUT = 4.0V, ramped load VOUT = 0V S3# = 0, VOUT = 4.0V, ramped load VOUT = 0V, COUT = 100F High-to-Low transition Low-to-High transition 0.8 0.8 0.65 105 150 80 1.5 1.7 200 VS3/EN = 5V, 0V Outputs are off, VOUT = 0 Outputs latched off -1 -10 1 1 10 2.0 100 500 140 700 2.0 1.8 195 5.0 0.6 +10 5.5 1 5 4.0 3.8 Units V A A A V mA A V V mV m m A A mA mA V V mV A A mA
MAIN Supply Current Switches Off S3# = 1, no load Note 5, (MIC20x2-1, MIC20x2-2 only) MAIN Reverse Leakage Current, AUX Supply Voltage AUX Supply Current, both switches on, Note 5 AUX Supply Current, switches off. (MIC20x2-1, MIC20x2-2 only) AUX Undervoltage Lockout Threshold AUX Undervoltage Lockout Hysteresis MAIN On-Resistance, Each Output AUX On-Resistance, Each Output MAIN Current-Limit Threshold MAIN Short-Circuit Current-Limit AUXCurrent-Limit Threshold AUX Short-Circuit Current-Limit S3#, EN1, EN2. Input Threshold Voltage (EN1, EN2, for MIC20x2-x only) EN1, EN2 and S3# Input Hysteresis (EN1, EN2, for MIC20x2-x only) S3#, EN1, EN2 Input Current (EN1, EN2, for MIC20x2-x only) OUT1, OUT2 Leakage Current (MIC2012-x, MIC2072-x only) Pull-Up Current During Latched Output State (MIC2072-1, -2) S3# = 0, both switches ON, VMAIN = 0V
VHYS IIN IOFF
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MIC2012
Symbol VTH LATCH Parameter Latch Reset Threshold (MIC2072, MIC2072-x only) 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 IFAULT = 5mA IFAULT = -20A VFAULT = 5V Figure 5 Figure 5 Output shorted to ground, Figure 4 Output shorted to ground, Figure 4 MAIN output AUX output RL = 10, CL = 1F, Figure 3 RL = 10, CL = 1F, Figure 3 RL = 10, CL = 1F, Figure 3 RL = 10, CL = 1F, Figure 3 RL = 50, CL = 1F, Figure 3 RL = 50, CL = 1F, Figure 3 RL = 50, CL = 1F, Figure 3 RL = 50, CL = 1F, Figure 3 S3# transition to 0 S3# transition to 1 5 0 5 10 20 4 0.2 10 Condition VOUT Rising Min Typ 1.95 0.4 Max
Micrel
Units V V/s
140 120 160 150 0.2
C C C C V V A ms ms ms
VOL VOH
FAULT Output Low Voltage FAULT Output High Voltage (MIC2012-1P,-2P),(MIC2072-1P,-2P) FAULT Output Off Current (Not Applicable to 'P' Options)
TH TS tDLY tOC
MAIN to S3# Hold Time, Note 6 MAIN to S3# Set-up Time, Note 6 FAULT Delay Filter Response Time (Overcurrent only), Note 7 Overcurrent Response Time
2 2 2 35 2 32 0.6 120 0.5 115 5 5 7.5 7.5
s s ms s ms s ms s ms s ms ms
tON(MAIN) tOFF(MAIN) tr(MAIN) tf(MAIN) tON(AUX) tOFF(AUX) tr(AUX) tf(AUX) tXMA tXAM
Note 1. Note 2. Note 3. Note 4. Note 5. Note 6. Note 7. Note 8.
MAIN Output Turn-On Time MAIN Output Turn-Off Time (MIC20x2-x only) MAIN Output Rise Time MAIN Output Fall Time (MIC20x2-x only) AUX Output Turn-On Time AUX Output Turn-Off Time (MIC20x2-x only) AUX Output Rise Time AUX Output Fall Time (MIC20x2-x only) MAIN to AUX Cross Conduction Time, Note 8 AUX to MAIN Cross Conduction Time, Note 8
Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. All voltages are referenced to ground. 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. Guaranteed by design. Not production tested. 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. Cross conduction time is the duration in which both MAIN and AUX internal switches are on subsequent to S3# transitioning.
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MIC2012/2072
MIC2012
Micrel
Timing Diagrams
VE N 50% tO F F tON VOUT 90% 10%
Figure 2. MIC2012/72-1
VE N
50% tO F F tON
VOUT
90% 10%
Figure 3. MIC2012/72-2
Output shorted to ground
VOUT IOUT FAULT# ILIMIT tOC tDLY
Figure 4. Overcurrent Response Timing
tH MAIN S3# 1.5V
tS
1.5V
Figure 5. MAIN to S3# Timing
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MIC2012
Micrel
VOUT Device Under OUT Test IOUT RL CL
Test Circuit
tr VOUT 10% 90% 90% 10%
tf
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MIC2012/2072
MIC2012
Micrel
Typical Characteristics
Main Supply Current vs. Temperature
(Main 1 and Main 2 = ON)
Main Supply Current vs. Temperature
(Main 1 and Main 2 = OFF)
Main Short-Circuit Current-Limit vs. Temperature
1.30 1.25 1.20 1.15 5.5V AUX 1.10 5.0V AUX 4.5V AUX 0 20 40 60 TEMPERATURE (C) 80 100
V MAIN = 5.0V = S3# = 4.5, 5.0, 5.5V V
AUX
30
V MAIN = 4.5, 5.0, 5.5V
25 20 15
EN1 = EN2 = [ON],V
AUX
= S3# = 5.0V
0.25 0.225 0.2 0.175 0.15 0.125 0.1 0.075 0.05
V MAIN = 4.5, 5.0, 5.5V EN1 = EN2 = [OFF],V
AUX
= S3# = 5.0V
5.5V MAIN 5.0 V MAIN
5.5V MAIN
5.0 V MAIN
4.5 V MAIN 10 5 0 -40 -20
4.5 V MAIN IOUT = 0A 0 20 40 60 TEMPERATURE (C) 80 100 1.05 1.00 -40 -20
IOUT = 0A 0 20 40 60 TEMPERATURE (C) 80 100
0.025 0 -40 -20
Main Short-Circuit Current-Limit Threshold vs. Temperature
1.40 1.35 1.30 1.25 1.20 4.5V AUX 1.15 1.10 -40 -20 0 20 40 60 TEMPERATURE (C) 80 100 5.0V AUX
V MAIN = 5.0V = S3# = 4.5, 5.0, 5.5V V
AUX
Main Rise-Time vs. Temperature
(EN Toggled)
AUX Supply Current vs. Temperature
(AUX 1 and AUX 2 = ON)
2000 1800 1600 1400 1200 1000 800 600 400
V MAIN = 5.0V V AUX = S3# = 4.5, 5.0, 5.5V
1000 4.5V AUX
V AUX = 4.5, 5.0, 5.5V 900 V = S3# = 0V MAIN 800 700 600 500 400 4.5 V AUX 300 200 100 -40 -20
5.5V AUX
5.5V AUX
5.0 V AUX
5.0 V AUX IOUT = 0A EN1 = EN2 = [ON]
5.5 V AUX
R L = 10 C L = 1F 80 100
200 -40 -20
0 20 40 60 TEMPERATURE (C)
0 20 40 60 TEMPERATURE (C)
80 100
AUX Supply Current vs. Temperature
(AUX 1 and AUX 2 = OFF)
Enable Threshold (increasing) vs. Temperature
(MIC2012-1/-2) 2.2
2.0
Enable Threshold (decreasing) vs. Temperature
(MIC2012-1/-2) V AUX = 4.5, 5.0, 5.5V V MAIN = S3# = 5.0V
1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30
V AUX = 4.5, 5.0, 5.5V V MAIN = S3# = 0V I OUT = 0A EN1 = EN2 = [OFF]
2.0 1.8
5.5V AUX
1.8 1.6
5.0 V AUX 1.6
5.5V AUX 4.5 V AUX
5.5V AUX
4.5 V AUX V AUX = 4.5, 5.0, 5.5V V MAIN = S3# = 5.0V 0 20 40 60 TEMPERATURE (C) 80 100
1.4 1.2
4.5 V AUX 5.0 V AUX
0.20 5.0 V AUX 0.10 0.00 -40 -20 0 20 40 60 TEMPERATURE (C)
1.4
80 100
1.2 -40 -20
1.0 -40 -20
0 20 40 60 TEMPERATURE (C)
80 100
Enable Threshold (increasing) vs. Temperature
(MIC2012-1/-2) 2.2 2.0 5.5V MAIN 1.8 1.6 1.4 V MAIN = 4.5V to 5.5V V AUX = S3# = 5.0V 1.2 -40 -20 0 20 40 60 TEMPERATURE (C) 80 100 4.5V MAIN 5.0V MAIN
Enable Threshold (decreasing) vs. Temperature (MIC2012-1/-2)
2.0 1.8 1.6 1.4 1.2 5.5V MAIN V MAIN = 4.5V to 5.5V V AUX = S3# = 5.0V 0 20 40 60 TEMPERATURE (C) 80 100 4.5V MAIN 5.0V MAIN
1800 1600 1400 1200 1000 800 600 400
Pull-Up Current vs. Temperature
(Output Latched Off-MIC2072) V MAIN = 5.0 V V AUX = S3# = 4.5, 5.0, 5.5V 5.5V AUX
5.0V AUX 4.5V AUX
1.0 -40 -20
200 -40 -20
0 20 40 60 TEMPERATURE (C)
80 100
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Micrel
Output Reset Threshold vs. Temperature
3.00 2.75 2.50 2.25 2.00 1.75 1.50 -40 -20 4.5V AUX 5.0V AUX 80 100
V V
(Output Latched Off -MIC2072) V OUT Rising
MAIN AUX = 5.0 V = S3# = 4.5, 5.0, 5.5V
5.5V AUX
0 20 40 60 TEMPERATURE (C)
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MIC2012
Micrel
Functional Characteristics
AUX Start-up by UVLO AUX Shutdown by UVLO
IOUT VOUT FAULT VAUX (50mA/div) (2V/div) (2V/div) (2V/div)
TIME (500s/div)
IOUT (50mA/div)
VAUX ramps from 0V to 5V VMAIN = S3# = 0V = 5V VMAIN = V EN = [ON] AUX RLOAD = 50CL = 100F CLOAD = 1F RL = 10
VOUT FAULT VAUX (2V/div) (2V/div) (2V/div)
2.96V
VAUX ramps from 5V to 0V VMAIN = S3# = 0V EN = [ON] RLOAD = 50 CLOAD = 1F
VMAIN = VAUX = 5V CL = 100F RL = 10
TIME (10ms/div)
Main Start-up by UVLO
VMAIN = VAUX;VMAIN & VAUX ramp from 0V to 5V S3# = 5V EN = [ON] RLOAD = 10 3.20V CLOAD = 1F
Main Shut-down by UVLO
2.96V
IOUT VOUT FAULT VMAIN (200mA/div) (2V/div)(2V/div) (2V/div)
IOUT VOUT FAULT VMAIN (200mA/div) (2V/div) (2V/div) (2V/div)
S3# = 5V EN = [ON] RLOAD = 101/2 CLOAD = 1F VMAIN = VAUX;VMAIN & VAUX ramp from 5V to 0V TIME (10ms/div)
TIME (500s/div)
Main Turn-On Response
Main Turn-Off Response
FAULT EN (5V/div) (5V/div)
VOUT (2V/div)
VOUT (5V/div)
FAULT EN (5V/div) (5V/div)
IOUT (200mA/div)
TIME (250s/div)
IOUT (200mA/div)
VMAIN = VAUX =5V S3# = 5V EN toggles from [OFF] to [ON] RLOAD = 10 CLOAD = 1F
VMAIN = VAUX =5V S3# = 5V EN toggles from [ON] to [OFF] RLOAD = 10 CLOAD = 1F
TIME (100s/div)
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MIC2012
Micrel
AUX Turn-On Response
AUX Turn-Off Response
VOUT FAULT EN (5V/div) (5V/div) (5V/div)
FAULT EN (5V/div) (5V/div)
IOUT (50mA/div)
TIME (100s/div)
IOUT (50mA/div)
VAUX =5V VMAIN = S3# = 0V EN toggles from [OFF] to [ON] RLOAD = 50 CLOAD = 1F
VOUT (5V/div)
VAUX =5V VMAIN = S3# = 0V EN toggles from [ON] to [OFF] RLOAD = 50 CLOAD = 1F
TIME (100s/div)
Turn-On from S3# to AUX
VOUT FAULT S3# (5V/div) (5V/div) (5V/div)
Turn-Off from AUX to S3#
IOUT (50mA/div)
TIME (100s/div)
IOUT (50mA/div)
VAUX =5V, VMAIN = 0V EN = [ON] S3# toggles from [HI] to [LOW] RLOAD = 50 CLOAD = 1F
VOUT (2V/div)
FAULT S3# (5V/div) (5V/div)
VAUX =5V, VMAIN = 0V S3# toggles from [LO] to [HI] EN = [ON] RLOAD = 50 CLOAD = 1F
TIME (1ms/div)
Main Inrush Current into CLOAD
VOUT FAULT EN (5V/div) (5V/div) (5V/div) FAULT (5V/div)
Main-Ramped to Short by MOSFET
CL = 560F
IOUT (500mA/div) IOUT (500mA/div)
VOUT (2V/div)
VMAIN = VAUX = 5V S3# = 5V EN toggles from [OFF] to [ON] RLOAD = OPEN CLOAD = 10F, 100F, 560F
1.4A VMAIN = VAUX =5V S3# = 5V, EN = [ON] CLOAD = 1F RLOAD toggles from > 1k to <0.5 TIME (50ms/div)
CL = 100F
CL = 10F TIME (500s/div)
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MIC2012
Micrel
AUX Ramped to Short by MOSFET
FAULT (5V/div)
Main Turn-On into Short
VOUT FAULT EN (5V/div) (5V/div) (5V/div)
VAUX = 5V VMAIN = S3# = 0V, EN = [ON] RLOAD toggles from >1k to <0.5 CLOAD = 1F
VOUT (2V/div)
1.2A
IOUT (100mA/div)
TIME (25ms/div)
IIN (500mA/div)
VMAIN = VAUX =5V S3# = 5V EN toggles from [OFF] to [ON] RLOAD = Short CLOAD = 1F
TIME (2.5ms/div)
AUX Turn-On into Short
VAUX =5V VMAIN = S3# = 0V EN toggles from [OFF] to [ON] CLOAD = 100F
VOUT FAULT EN (5V/div) (10V/div) (5V/div)
AUX Inrush Current into Large CLOAD
VOUT FAULT EN (2V/div) (5V/div) (5V/div)
230mA
VAUX =5V VMAIN = S3#= 0V EN toggles from [OFF] to [ON] ILOAD < 10mA CLOAD = 220F
IOUT (100mA/div)
TIME (2.5ms/div)
IIN (50mA/div)
TIME (2.5ms/div)
AUX Inrush Current into Small CLOAD
VOUT FAULT EN (5V/div) (10V/div) (5V/div) S3# VOUT (5V/div) (5V/div)
Main-to-AUX Cross Conduction
IIN (50mA/div)
IMAIN (50mA/div)
IAUX (50mA/div)
VAUX =5V VMAIN = S3# = 0V EN toggles from [OFF] to [ON] ILOAD < 10mA CLOAD = 10F
VMAIN = VAUX = 5V S3# toggles from [HI] to [LO] EN = [ON] RLOAD = 50 950s C = 1F
LOAD
TIME (100s/div)
TIME (250s/div)
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Micrel
AUX-to-Main Cross Conduction
S3# (5V/div) VOUT (5V/div)
VMAIN = VAUX =5V S3# toggles from [LO] to [HI] EN = [ON] RLOAD = 50 CLOAD = 1F
IAUX (50mA/div)
3.96ms
IMAIN (50mA/div)
TIME (1ms/div)
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MIC2012
Micrel
MAIN Current Limit
Functional Diagram
MAIN FET
EN
Charge Pump + Gate Control
AUX FET
OUT
S3# Current Limit
AUX
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 500m, 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 100m, 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 140C and the overheated channel is in current limit. The other channel is not affected. If, however, the die temperature exceeds 160C, 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) x 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 x JA + TA where: TJ = junction temperature TA = ambient temperature JA = 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 120C. 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 dead short on the output. 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
EN (MIC2010-2) VOUT FAULT
Thermal Shutdown Reached
Micrel exceeds the current-limit threshold. The FAULT response delay time tDLY is typically 10ms. 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
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
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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. (c) 2004 Micrel Incorporated
MIC2012/2072
16
January 2005

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