MIC2090/MIC2091
Current Limiting Power
Distribution Switches
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
General Description
The MIC2090 and MIC2091 are high-side MOSFET power
switches optimized for general-purpose 50mA or 100mA
low power distribution in circuits requiring over-current
limiting and circuit protection. Typical applications for these
parts are for switching power in USB ports, portable
consumer items, camera and camcorder motor protection,
thermal printer head protection, and many other low
current-load switching applications.
The MIC2090 and MIC2091 come in two versions: auto-
retry current limit and output latch off on an over current
fault. The MIC2090 and MIC2091 are offered in a space
saving 5-pin SOT-23 package with an operating junction
temperature range of -40°C to +125°C.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
• 1.8V to 5.5V supply voltage
• 790 m typical RDSON at 3.3V
• MIC2090 is rated for 50mA minimum continuous current
• MIC2091 is rated for 100mA minimum continuous
current
• Reverse current blocking (OGI)
• 20ns super fast reaction time to hard short at output
• 10ms fault flag delay (tD_FAULT/) eliminates false
assertions
• Auto-retry overcurrent and short-circuit protection (-1
version)
• Latch-off on current limit (-2 version)
• Thermal shutdown
• Fault status flag indicates: over-current, over-
temperature, or UVLO
• Under-voltage lockout (UVLO)
• Low quiescent current
Applications
• USB peripherals
• Camcorder
• DSC
• MP3/iPod
• SD protection
• USB low-power hub
_________________________________________________________________________________________________________________________
Typical Application
MIC2091 USB Power Switch Startup into Short Circuit
July 2011 M9999-070611-B
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July 2011 2 M9999-070611-B
Ordering Information
Part Number Marking Current
Limit
Current-Limit
Recovery
Junction Temperature
Range Package
MIC2090-1YM5 L1K 50mA Auto-Retry –40°C to +125°C SOT-23-5
MIC2091-1YM5 M1K 100mA Auto-Retry –40°C to +125°C SOT-23-5
MIC2090-2YM5 L2K 50mA Latch-Off –40°C to +125°C SOT-23-5
MIC2091-2YM5 M2K 100mA Latch-Off –40°C to +125°C SOT-23-5
Pin Configuration
5-Pin SOT-23 (M5)
Pin Description
Pin Number Pin Name Pin Function
1 VIN
Supply (Input): +1.8V to +5.5V. Provides power to the output switch and the MIC2090/MIC2091
internal control circuitry.
2 GND Ground.
3 EN
Enable (Input): Active-high TTL compatible control input. A high signal turns on the internal
switch and supplies power to the load. This pin cannot be left floating.
4 FAULT/
Fault Status (Output): Open drain output. Can be connected to other open drain outputs. Must
be pulled high with an external resistor.
When EN=0, FAULT/ pin is high
When EN=1, a low on the FAULT/ pin indicates one or more of the following conditions:
1. The part is in current limit and is turned off.
2. The part is in thermal limit and is turned off.
3. The part is in UVLO
5 VOUT
Switched Output (Output): The voltage on this pin is controlled by the internal switch. Connect
the load driven by the MIC2090/MIC2091 to this pin.
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July 2011 3 M9999-070611-B
Absolute Maximum Ratings(1)
Supply Voltage (VIN)..................................... −0.3V to +6.0V
Output Voltage (VOUT). ................................. −0.3V to +6.0V
FAULT/ Pin Voltage (VFAULT/) ....................... −0.3V to +6.0V
FAULT/ Pin Current (I FAULT/) .......................................25mA
EN Pin Voltage (VEN)........................... −0.3V to (VIN + 0.3V)
Power Dissipation (PD)..............................Internally Limited
Maximum Junction Temperature (TJ)......................... 150°C
Storage Temperature (TS)......................... −65°C to +150°C
Lead Temperature (soldering, 10s)............................ 260°C
ESD HBM Rating(3)......................................................... 3kV
ESD MM Rating(3).........................................................200V
Operating Ratings(2)
Supply Voltage (VIN)..................................... +1.8V to +5.5V
Output Voltage (VOUT) .................................. +1.8V to +5.5V
EN Pin Voltage (VEN).............................................. 0V to VIN
FAULT/ Pin Voltage (VFAULT/) .............................. 0V to 5.5V
FAULT/ Pin Current (I FAULT/) .........................................1mA
Ambient Temperature (TA) ..........................–40°C to +85°C
Junction Temperature (TJ) ........................ –40°C to +125°C
Package Thermal Resistance
SOT23-5 (θJA) ...............................................252.7°C/W
Electrical Characteristics(4)
VIN = 5V; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C, unless noted.
Symbol Parameter Condition Min. Typ. Max. Units
Power Input Supply
VIN Input Voltage Range 1.8 5.5
V
Shutdown Current VEN ≤ 0.5V (switch off), VOUT = open 5
10
IVIN
Supply Current VEN ≥ 1.5V (switch on), VOUT = open 70
110
µA
VUVLO Under-Voltage Lockout
Threshold VIN rising 1.75 V
VUVLO_HYS Under-Voltage Lockout
Threshold Hysteresis 100 mV
Enable Input
Enable Logic Level High(5) V
IH (MIN) 1.5
VEN Enable Logic Level Low(5) V
IL (MAX)
0.5 V
IEN Enable Bias Current VEN = 5V 0.1 µA
tON Output Turn-On Delay RL = 500, CL = 0.1µF See “Timing Diagrams” 215 µs
tR Output Turn-On Rise Time RL = 500, CL = 0.1µF See “Timing Diagrams” 5 µs
tOFF Output Turn-Off Delay RL = 500, CL = 0.1µF See “Timing Diagrams” 125 µs
tF Output Turn-Off Fall Time RL = 500, CL = 0.1µF See “Timing Diagrams” 115 µs
Internal Switch
MIC2090 VIN = 5.0V, IOUT = 50mA 700 1200
MIC2090 VIN = 3.3V, IOUT = 50mA 790 1200
MIC2090 VIN = 1.8V, IOUT = 50mA 1300
MIC2091 VIN = 5.0V, IOUT = 100mA 700 1200
MIC2091 VIN = 3.3V, IOUT = 100mA 790 1200
RDSON On Resistance RDS(ON)
MIC2091 VIN = 1.8V, IOUT = 100mA 1300
m
Input-to-Output Leakage
Current (Forward leakage
Current)
MIC2090 and MIC2091, VEN ≤ 0.5V, (output
off), VIN = 5.5V, VOUT = 0V
10 A
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Electrical Characteristics(4) (Continued)
VIN = 5V; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C, unless noted.
Symbol Parameter Condition Min. Typ. Max. Units
Output to Input Leakage
Current (Reverse Leakage
Current)
MIC2090 and MIC2091, VEN ≤ 0.5V, (output
off), VOUT = 5.5V, VIN = 0V
10 µA
Current Limit
MIC2090 @ VOUT = 4.5V 50 75 100
MIC2090 @ VOUT = 0V 50 100 150
MIC2091 @ VOUT = 4.5V 100 150 200
ILIMIT Current-Limit Threshold
MIC2091 @ VOUT = 0V 100 175 250
mA
tSC_RESP Short-Circuit Response
Time
Short circuit applied to output after switch is
turned on, see “Timing Diagrams”. VIN = 3.3V. 20 ns
TAUTORESTART
Time After Switch Shuts
Down From An Over-
Current Condition Before
It Tries To Turn On Again.
30 60 90 ms
FAULT/ Flag
Error Flag Output Voltage Output voltage high (1mA Sinking) 0.4 V
tD_FAULT/
Time After Switch Comes
Into Current Limit Before
The PIN FAULT/ Is Pulled
Low.
When an over-current condition happens, the
part will go into constant output current for this
time. After this time it will turn off the output
and pull low the PIN FAULT/. The MIC2090-1
and MIC2091-1 will automatically restart
themselves after the auto restart time
TAUTORESTART.
5 10 20 ms
tR_FAULT/ FAULT/ Rising Time FAULT/ is connected to VIN = 5V through 10k
and 100pF in parallel. See “Timing Diagrams” 5 µs
tF_FAULT/ FAULT/ Falling Time 1 µs
Reverse Voltage Protection (OGI)
OGI Output Voltage Greater
Than Input Voltage (OGI)
If the output voltage is greater than the input
voltage by this amount, the part will shut down.
The enable pin must be recycled to reset.
85 mV
OGITIME
Time that the output voltage can be greater
than the input voltage before the chip is shut
down.
10 ms
Thermal Protection
TJ Rising 150
TOVERTEMP Over-Temperature
Shutdown TJ Falling 140
°C
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. VIL(MAX) = Maximum positive voltage applied to the input which will be accepted by the device as a logic low.
VIH(MIN) = Minimum positive voltage applied to the input which will be accepted by the device as a logic high.
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July 2011 5 M9999-070611-B
Timing Diagrams
Output Rise and Fall Times (tR, tF)
Switch Delay Time (tON, tOFF)
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July 2011 6 M9999-070611-B
Typical Characteristics
V
IN Shutdown Current
vs. Input Voltage
0
2
4
6
8
10
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
SUPPLY CURRENT (µA)
V
IN Supply Current
vs. Input Voltage
40
50
60
70
80
1.52.02.53.03.54.04.55.05.5
INPUT VOLTAGE (V)
SUPPLY CURRENT (µA)
Enable Thresholds
vs. Input Voltage
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
ENABLE THRESHOLD (V)
V
EN
Rising
V
EN
Falling
Current Limit vs. Input Voltage
MIC2090
70.0
80.0
90.0
100.0
110.0
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
CURRENT LIMIT (mA)
I
LIMIT
@ V
OUT
= 0.9V * V
OUT
I
LIMIT
@ V
OUT
= 0V
FAULT/ Delay vs. Input Voltage
(MIC2090)
7.0
7.2
7.4
7.6
7.8
8.0
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
DELAY (ms)
C
LOAD
= 10F
Auto-Reset Time vs. Input
Voltage (MIC2090)
58.0
58.5
59.0
59.5
60.0
60.5
61.0
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
DELAY (ms)
Current Limit vs. Input Voltage
MIC2091
150.0
160.0
170.0
180.0
190.0
200.0
210.0
220.0
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
CURRENT LIMIT (mA)
I
LIMIT
@ V
OUT
= 0.9V * V
OUT
I
LIMIT
@ V
OUT
= 0V
Switch On Resistance
vs. Input Voltage
0.5
0.7
0.9
1.1
1.3
1.5
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
RESISTANCE (Ω)
I
OUT
= 10mA
Output Turn-On Delay
vs. Input Voltage
185
190
195
200
205
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
DELAY (μs)
C
LOAD
= 0.1F
R
LOAD
= 500
Micrel, Inc. MIC2090/MIC2091
July 2011 7 M9999-070611-B
Typical Characteristics (Continued)
Output Rise Time
vs. Input Voltage
0
1
2
3
4
5
6
7
8
1.52.02.53.03.54.04.55.05.5
INPUT VOLTAGE (V)
RISE TIME (μs)
C
LOAD
= 0.1F
R
LOAD
= 500
Output T urn-Off Delay
vs. Input Voltage
29
30
31
32
33
34
35
1.52.02.53.03.54.04.55.05.5
INPUT VOLTAGE (V)
DELAY (μs)
C
LOAD
= 0.1F
R
LOAD
= 500
Output Fall Time
vs. Input Voltage
70
80
90
100
110
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
FALL TIME (μs)
C
LOAD
= 0.1F
R
LOAD
= 500
OGI Threshold
vs. Input Voltage
50
60
70
80
90
100
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
OGI THRESHOLD (mV)
OGI Delay
vs. Input Voltage
5
6
7
8
9
10
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
DELAY (ms)
V
IN
ShutdownCurrent
vs. Temperature
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
-40 -15 10 35 60 85
TEMPERATURE (°C)
SHUTDOWN CURRENT (µA)
V
IN
= 5V
V
IN
= 1.8V
V
IN
Supply Current
vs.Temperature
40
45
50
55
60
65
70
75
80
-40 -15 10 35 60 85
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
V
IN
= 5V
V
IN
= 1.8V
R
LOAD
= 0
Enable Threshold
vs. Temperature
1.00
1.05
1.10
1.15
1.20
1.25
1.30
1.35
1.40
-40 -15 10 35 60 85
TEMPERATURE (°C)
ENABLE THRESHOLD (V)
V
EN
Rising
V
EN
Falling
V
IN
= 5.0V
Current Limit vs. Temperature
(MIC2090)
70
72
74
76
78
80
82
84
86
88
90
92
94
96
-40 -15 10 35 60 85
TEMPERATURE (°C)
CURRENT LIMIT (mA)
V
IN
= 5.0V
I
LIMIT
@ V
OUT
= 0V
I
LIMIT
@ V
OUT
= 4.5V
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July 2011 8 M9999-070611-B
Typical Characteristics (Continued)
Current Limit vs.
Temperature (MIC2090)
70
75
80
85
90
95
100
105
110
-40 -15 10 35 60 85
TEMPERATURE (°C)
CURRENT LIMIT (mA)
V
IN
= 1.8V
I
LIMIT
@ V
OUT
= 0V
I
LIMIT
@ V
OUT
= 1.6V
FAULT/ Delay vs. Temperature
(MIC2090)
6.5
7.0
7.5
8.0
8.5
-40 -15 10 35 60 85
TEMPERATURE (°C)
DELAY (ms)
V
IN
= 5V
V
IN
= 1.8V
Auto-Reset Time vs.
Temperature (MIC2090)
58
59
60
61
62
63
64
65
66
-40 -15 10 35 60 85
TEMPERATURE (°C)
DELAY (ms)
V
IN
= 1.8V
V
IN
= 5.0V
Current Limit vs. Temperature
(MIC2091)
140
150
160
170
180
190
200
210
220
230
240
-40 -15 10 35 60 85
TEMPERATURE (°C)
CURRENT LIMIT (mA)
V
IN
= 1.8V
I
LIMIT
@ V
OUT
= 0V
I
LIMIT
@ V
OUT
= 1.6V
Current Limit vs. Temperature
(MIC2091)
140
150
160
170
180
190
-40 -15 10 35 60 85
TEMPERATURE (°C)
CURRENT LIMIT (mA)
V
IN
= 5.0V
I
LIMIT
@ V
OUT
= 0V
I
LIMIT
@ V
OUT
= 4.5V
R
DS(ON)
vs. Temperature
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
-40 -15 10 35 60 85
TEMPERATURE (°C)
RESISTANCE (Ω)
V
IN
= 5.0V
V
IN
= 1.8V
I
OUT
= 10mA
Output Turn-On Delay
vs. Temperature
185
190
195
200
205
210
215
-40 -15 10 35 60 85
TEMPERATURE (°C)
DELAY (μs)
V
IN
= 1.8V
V
IN
= 5.0V
C
LOAD
= 0.1F
R
LOAD
=500
Output Rise Time
vs. Temperature
0
1
2
3
4
5
6
7
-40 -15 10 35 60 85
TEMPERATURE (°C)
RISE TIME (μs)
V
IN
= 1.8V
V
IN
= 5.0V
C
LOAD
= 0.1F
R
LOAD
=500
Output Turn-Off Delay
vs. Temperature
25
27
29
31
33
35
-40 -15 10 35 60 85
TEMPERATURE (°C)
DELAY (μs)
V
IN
= 1.8V
V
IN
= 5.0V
C
LOAD
= 0.1F
R
LOAD
=500
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July 2011 9 M9999-070611-B
Typical Characteristics (Continued)
Output Fall Time
vs. Temperature
60
70
80
90
100
110
120
-40 -15 10 35 60 85
TEMPERATURE (°C)
FALL TIME (μs)
V
IN
= 1.8V
V
IN
= 5.0V
C
LOAD
= 0.1F
R
LOAD
=500
OGI Threshold
vs. Temperature
0
20
40
60
80
100
120
-40 -15 10 35 60 85
TEMPERATURE (°C)
OGI THRESHOLD (mV)
V
IN
= 1.8V
V
IN
= 5.0V
OGI Delay
vs. Temperature
7.6
7.8
8.0
8.2
8.4
8.6
8.8
9.0
-40 -15 10 35 60 85
TEMPERATURE (°C)
DELAY (ms)
V
IN
= 1.8V
V
IN
= 5.0V
V
IN
UVLO Thresholds
vs. Temperature
1.0
1.1
1.2
1.3
1.4
-40 -15 10 35 60 85
TEMPERATURE (°C)
V
IN
ULVO THRESHOLDS (V)
V
IN
Rising
V
IN
Falling
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July 2011 10 M9999-070611-B
Functional Characteristics
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July 2011 11 M9999-070611-B
Functional Characteristics (Continued)
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July 2011 12 M9999-070611-B
Functional Characteristics (Continued)
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July 2011 13 M9999-070611-B
Functional Characteristics (Continued)
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July 2011 14 M9999-070611-B
Functional Diagram
MIC2090/MIC2091 Functional Diagram
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July 2011 15 M9999-070611-B
Functional Description
VIN and VOUT
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.
When the switch is disabled, current will not flow to the
load, except for a small unavoidable leakage current of a
few microamps (forward leakage current).
CIN
A minimum 1F bypass capacitor positioned close to the
VIN and GND pins of the switch is both good design
practice and required for proper operation of the switch.
This will control supply transients and ringing. Without a
sufficient bypass capacitor, large current surges or a
short may cause sufficient ringing on VIN (from supply
lead inductance) to cause erratic operation of the
switch’s control circuitry. For best performance, place a
ceramic capacitor next to the IC.
An additional 10µF (or greater) capacitor, positioned
close to the VIN and GND pins of the switch is
necessary if the distance between a larger bulk capacitor
and the switch is greater than three inches. This
additional capacitor limits input voltage transients at the
switch caused by fast changing input currents that occur
during a fault condition, such as current limit and thermal
shutdown.
When bypassing with capacitors of 10F or more, 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
0.1F to 1F are recommended. Again, good quality,
low-ESR capacitors, preferably ceramic, should be
chosen.
COUT
An output capacitor is required to reduce ringing and
voltage sag on the output during a transient condition. A
value between 1F and 10F is recommended.
A 10F or larger capacitor should be used if the distance
between the MIC2090/MIC2091 and the load is greater
than three inches. The internal switch in the
MIC2090/MIC2091 turns off in (typically) 20ns. This
extremely fast turn-off can cause an inductive spike in
the output voltage when the internal switch turns off
during an overcurrent condition. The larger value
capacitor prevents the output from glitching too low.
Limitations on COUT
The part may enter current limit when turning on with a
large output capacitance, which is an acceptable
condition. However, if the part remains in current limit for
a time greater than tD_FAULT, the FAULT/ pin will assert
low. The maximum value of COUT may be approximated
by Equation 1:
IN_MAX
ND_FAULT_MILIMIT_MIN
OUT_MAX V
TI
C
×
= Eq. 1
Where: ILIMIT_MIN and TD_FAULT_MIN are the minimum
specified values listed in the Electrical Characteristic
table and VIN_MAX is the maximum input voltage to the
switch.
Current Sensing and Limiting
The MIC2090/MIC2091 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 the over-
current threshold. When current limiting is activated in
the -1 version, 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 switch goes into
thermal shutdown. If the overcurrent fault is large
enough to drop VOUT below (typically) 1.8V, the internal
MOSFET turns off very quickly (typically 20ns). This
prevents excessive current from flowing through the
device and damaging the internal MOSFET.
The latch-off feature of the -2 version latches the output
off when the output current exceeds the overcurrent
threshold. VIN or the enable pin must be toggled to reset
the latch.
Enable Input
The EN pin is a TTL logic level compatible input which
turns the internal MOSFET switch on and off. The
FAULT/ pin remains high when the EN pin is pulled low
and the output is turned off. Toggling the enable pin
resets the output after an OGI (output greater than input)
condition occurs. In the -2 version, toggling the enable
pin resets the output after an overcurrent event.
Fault Output
The FAULT/ is an N-channel open-drain output, which is
asserted LOW when the MIC2090/MIC2091 switch
either begins current limiting or enters thermal shutdown.
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July 2011 16 M9999-070611-B
During an overcurrent or short circuit, The FAULT/ signal
asserts after a brief delay period, tD_FAULT/, in order to
filter out false or transient over-current conditions.
The FAULT/ output is open-drain and must be pulled
HIGH with an external resistor. The FAULT/ signal may
be wire-OR’d with other similar outputs, sharing a single
pull-up resistor.
Power Dissipation and Thermal Shutdown
Thermal shutdown is used to protect the
MIC2090/MIC2091 switch from damage should the die
temperature exceed a safe operating temperature.
Thermal shutdown shuts off the output MOSFET and
asserts the FAULT/ output if the die temperature
reaches the over-temperature threshold, TOVERTEMP.
The switch will automatically resume operation when the
die temperature cools down to 140°C. If resumed
operation results in reheating of the die, another
shutdown cycle will occur and the switch will continue
cycling between ON and OFF states until the reason for
the overcurrent condition has been resolved.
Depending upon the PCB layout, package type, ambient
temperature, etc., hundreds of milliseconds may elapse
from the time a fault occurs to the time the output
MOSFET will be shut off. This delay is caused because
of the time it takes for the die to heat after the fault
condition occurs.
Power dissipation depends on several factors such as
the load, PCB layout, ambient temperature, and supply
voltage. Calculation of power dissipation can be
accomplished by Equation 2:
PD = RDS(ON) × (IOUT)2 Eq.2
To relate this to junction temperature, Equation 3 can be
used:
TJ = PD × Rθ(J-A) + TA Eq. 3
Where:
TJ = Junction Temperature
TA = Ambient Temperature
Rθ(J-A) is the thermal resistance of the package.
In normal operation, excessive switch heating is most
often caused by an output short circuit. If the output is
shorted, when the switch is enabled, the
MIC2090/MIC2091 switch limits the output current to the
maximum value. The heat generated by the power
dissipation of the switch continuously limiting the current
may exceed the package and PCB’s ability to cool the
device and the MIC2090/MIC2091 will shut down and
signal a fault condition. Please see the “Fault Output”
description for more details on the FAULT/ output.
After the MIC2090/MIC2091 shuts down, and cools, it
will re-start itself if the enable signal remains true.
n Figure 2, die temperature is plotted against IOUT
assuming a constant ambient temperature of 85°C and a
worst case internal switch on-resistance (RON). This plot
is valid for both the MIC2090 and MIC2091.
Die Temperature vs. Output Current
(Ambient Temperature = 85°C)
83
84
85
86
87
88
89
90
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
I
OUT
(A)
DIE TEMPERATURE (°C)
Figure 2. Die Temperature vs. IOUT
ILIMIT vs. IOUT Measured (-1 version only)
When the MIC2090/MIC2091 is current limiting, it is
designed to act as a constant current source to the load.
As the load tries to pull more than the maximum current,
VOUT drops and the input to output voltage differential
increases. When VOUT drops below 1.8V, then the output
switch momentarily turns off to insure the internal
MOSFET switch is not damaged by a very fast short
circuit event.
When measuring IOUT in an overcurrent condition, it is
important to remember voltage dependence, otherwise
the measurement data may appear to indicate a problem
when none really exists. This voltage dependence is
illustrated in Figures 3 and 4.
In Figure 3, output current is measured as VOUT is pulled
below VIN, with the test terminating when VOUT is 2.5V
below VIN. Observe that once ILIMIT is reached IOUT
remains constant throughout the remainder of the test.
Figure 4 repeats this test but simulates operation deeper
into an overcurrent condition. When VOUT drops below
1.8V, the switch turns off for a few microseconds before
turning back on.
Micrel, Inc. MIC2090/MIC2091
July 2011 17 M9999-070611-B
Figure 3. IOUT in Current Limiting for VOUT > 1.8V
Figure 4. IOUT in Current Limiting for VOUT < 1.8V
Under-Voltage Lock Out (UVLO)
The MIC2090/MIC2091 switches have an Under-Voltage
Lock Out (UVLO) feature that will shut down the switch
in a reproducible way when the input power supply
voltage goes too low. The UVLO circuit disables the
output until the supply voltage exceeds the UVLO
threshold. Hysteresis in the UVLO circuit prevents noise
and finite circuit impedance from causing chatter during
turn-on and turn-off. While disable by the UVLO circuit,
the output switch (power MOSFET) is OFF and no circuit
functions, such as FAULT/ or EN, are considered to be
valid or operative.
OGI (Output Greater th an Input)
The internal MOSFET switch turns off when it senses an
output voltage that is greater than the input voltage.
This feature prevents continuous current from flowing
from the output to the input.
If the output voltage rises above VIN by the OGI
threshold voltage (typically 85mV), the internal MOSFET
switch turns off after a period of time, specified in the
electrical characteristics table as OGITIME. The FAULT/
pin remains high during and after an OGI event.
Figure 5 shows the output voltage, input current and
FAULT/ pin voltage when the output voltage is raised
above the input. Reverse current flows through the
internal MOSFET switch for the OGITIME period, until the
internal MOSFET switch is turned off and the input
current goes to 0A.
Figure 5. OGI Event
Micrel, Inc. MIC2090/MIC2091
July 2011 18 M9999-070611-B
MIC2090/MIC2091 Evaluation Board Schematic
Micrel, Inc. MIC2090/MIC2091
July 2011 19 M9999-070611-B
Bill of Materials
Item Part Number Manufacturer Description Qty.
C1, C2 08056D106MAT2A AVX(1) 10µF, 6.3V Ceramic Capacitor, X5R 2
C3, C4 NF (No Fill) 2
R1, R3 CRCW06031002FRT1 Vishay Dale(2) 10k, 1%, 0603 Resistor 2
R2 NF (No Fill) 1
U1 MIC2090-1YM5 Micrel, Inc.(3) Current Limiting Power Distribution Switch 1
U1 MIC2091-1YM5 Micrel, Inc.(3) Current Limiting Power Distribution Switch 0
U1 MIC2090-2YM5 Micrel, Inc.(3) Current Limiting Power Distribution Switch 0
U1 MIC2091-2YM5 Micrel, Inc.(3) Current Limiting Power Distribution Switch 0
Notes:
1. AVX: www.avx.com.
2. Vishay Tel: www.vishay.com.
3. Micrel, Inc.: www.micrel.com.
Micrel, Inc. MIC2090/MIC2091
July 2011 20 M9999-070611-B
PCB Layout Recommendations
Top Silk Screen
Top Copper
Micrel, Inc. MIC2090/MIC2091
July 2011 21 M9999-070611-B
PCB Layout Recommendations (Continued)
Bottom Copper
Bottom Silk Screen
Micrel, Inc. MIC2090/MIC2091
July 2011 22 M9999-070611-B
Package Information
5-Pin SOT23 (SOT23-5)
Micrel, Inc. MIC2090/MIC2091
July 2011 23 M9999-070611-B
Recommended Landing Pattern
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