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MIC2095/MIC2097/MIC2098/MIC2099
Current-Limiting Power Distribution Switches
General Description
The MIC2095/97/98/99 family of switches are selfcontained, current-limiting, high-side power switches, ideal for power-control applications. These switches are useful for general purpose power distribution applications such as digital televisions (DTV), printers, set-top boxes (STB), PCs, PDAs, and other peripheral devices. The current limiting switches feature either a fixed 0.5A/0.9A or resistor programmable output current limit. The family also has fault blanking to eliminate false noiseinduced, over current conditions. After an over-current condition, these devices automatically restart if the enable pin remains active. The MIC2097 switch offers a unique new patented Kickstart feature, which allows momentary high-current surges up to the secondary current limit (ILIMIT_2nd). This is useful for charging loads with high inrush currents, such as capacitors. The MIC2095/97/98/99 family of switches provides undervoltage, over-temperature shutdown, and output fault status reporting. The family also provides either an active low or active high, logic level enable pin. The MIC2095/97/98/99 family is offered in a space saving 1.6mm x 1.6mm Thin MLF(R) (TMLF) package. Datasheets and support documentation can be found on Micrel's web site at: www.micrel.com.
Features
* MIC2095: 0.5A fixed current limit * MIC2098: 0.9A fixed current limit * MIC2097/99: Resistor programmable current limit - 0.1A to 1.1A * * * * * * * * * * * * * * * * * MIC2097: Kickstart for high peak current loads Under voltage lock-out (UVLO) Soft start prevents large current inrush Automatic-on output after fault Thermal protection Enable active high or active low 170m typical on-resistance @ 5V 2.5V - 5.5V operating range Digital televisions (DTV) Set top boxes PDAs Printers USB / IEEE 1394 power distribution Desktop and laptop PCs Game consoles USB keyboard Docking stations
Applications
_________________________________________________________________________________________________________________________
Typical Application
MIC2095 USB Power Switch
MLF and MicroLeadFrame are registered 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
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Ordering Information
Part Number MIC2095-1YMT MIC2095-2YMT MIC2097-1YMT MIC2097-2YMT MIC2098-1YMT MIC2098-2YMT MIC2099-1YMT MIC2099-2YMT Marking J1K J2K K1K K2K H1K H2K G1K G2K ENABLE Logic Active High Active Low Active High Active Low Active High Active Low Active High Active Low Kickstart(TM) No No Yes Yes No No No No ILIMIT 0.5A 0.5A 0.1 A - 1.1A 0.1 A - 1.1A 0.9A 0.9A 0.1 A - 1.1A 0.1 A - 1.1A FAULT/ Output Yes Yes Yes Yes Yes Yes Yes Yes Junction Temperature (1) Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C Package 6-Pin 1.6mm x 1.6mm TMLF 6-Pin 1.6mm x 1.6mm TMLF 6-Pin 1.6mm x 1.6mm TMLF 6-Pin 1.6mm x 1.6mm TMLF 6-Pin 1.6mm x 1.6mm TMLF 6-Pin 1.6mm x 1.6mm TMLF 6-Pin 1.6mm x 1.6mm TMLF 6-Pin 1.6mm x 1.6mm TMLF
Pin Configuration
6-Pin 1.6mm x 1.6mm TMLF (MT) (Top View) MIC2095-1YMT/MIC2098-1YMT
6-Pin 1.6mm x 1.6mm TMLF (MT) (Top View) MIC2095-2YMT/MIC2098-2YMT
6-Pin 1.6mm x 1.6mm TMLF (MT) (Top View) MIC2097-1YMT / MIC2099-1YMT
6-Pin 1.6mm x 1.6mm TMLF (MT) (Top View) MIC2097-2YMT / MIC2099-2YMT
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Pin Description
Pin Number 1 2 (MIC2095/MIC2098) 2 (MIC2097/MIC2099) 3 4 (MIC2095-1/MIC2097-1/ MIC2098-1/MIC2099-1) 4 (MIC2095-2/MIC2097-2/ MIC2098-2/MIC2099-2) 5 6 EP Pin Name VOUT NC ILIMIT FAULT/ Pin Function Switch output (Output): The load being driven by the switch is connected to this pin. No Connect; Pin not used. Current Limit (Input): A resistor from this pin to ground sets the current limit value. See the "setting ILMIIT" section for details on setting the resistor value. Fault status (Output): A logic low on this pin indicates the switch 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 FAULT/ outputs from multiple devices. Switch Enable (Input): Logic high on this pin enables the switch. Switch Enable (Input): Logic low on this pin enables the switch. Ground. Power input (Input): This pin provides power to both the output power switch and the internal control circuitry. Used to remove heat from die. Connect to ground. Use multiple vias to the ground plane to minimize thermal impedance. See Applications Section for additional information.
ENABLE ENABLE/ GND VIN EP
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Absolute Maximum Ratings(1)
Supply Voltage (VIN) ....................................... -0.3V to 6.0V Output Voltage (VOUT) ....................................... -0.3V to VIN FAULT Pin Voltage (VFAULT) .............................. -0.3V to VIN ENABLE Pin Voltage (VENABLE).......................... -0.3V to VIN ILIMIT Pin Voltage (VILIMIT) ................................ -0.3V to VIN Power Dissipation (PD) ..............................Internally Limited Maximum Junction Temperature (TJ)......................... 150C Storage Temperature (Ts).........................-65C to +150C Lead Temperature (soldering, 10sec.)....................... 260C ESD HBM Rating (VOUT, GND)(3) ................................. 4kV ESD HBM Rating (FAULT, ENABLE, VIN)(3) ................. 2kV
Operating Ratings(2)
Supply Voltage (VIN)......................................... 2.5V to 5.5V ENABLE Pin Voltage (VENABLE) .............................. 0V to VIN FAULT Pin Voltage (VFAULT) ................................... 0V to VIN Ambient Temperature Range (TA) .............. -40C to +85C Package Thermal Resistance(6) 1.6mm x 1.6mm TMLF (JA) .............................. 93C/W
Electrical Characteristics(4)
VIN = 5V; CIN = 1F TA = 25C unless noted, bold values indicate -40C TA +85C. Symbol Power Input Supply VIN Input Voltage Range Quiescent Supply Current(5) IIN Shutdown Current Switch = ON Active Low Enable, VEN = 0V Active High Enable, VEN = 1.5V Switch = OFF Active Low Enable, VEN = 1.5V Switch = OFF Active High Enable, VEN = 0.5V VIN Rising UVLOTHRESHOLD VIN UVLO Threshold VIN Falling VIN UVLO Hysteresis Enable Control VEN IEN tON_DLY tOFF_DLY tRISE ENABLE Logic Level Low(5) ENABLE Logic Level High ENABLE Bias Current Output Turn-on Delay Output Turn-off Delay Output Turn-on rise time
(5)
Parameter
Condition
Min.
Typ.
Max.
Units
2.5 80
5.5 300
V A
8 0.1 2 1.9 2.25 2.15 100
15 5 2.5 2.4
A A V V mV
VIL(MAX) VIH(MIN) 0V VEN 5V RL = 43, CL = 120F VEN = 50% to VOUT = 10% RL = 43, CL = 120F VEN = 50% to VOUT = 90% RL = 100, CLOAD = 1F VOUT = 10% to 90% 500 1000 1.5 0.1 1000
0.5
V V
5 1500 700 1500
A s s s
Thermal Protection OTThreshold Over-temperature Shutdown TJ Rising TJ Falling 145 135 C C
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Electrical Characteristics (Continued)
VIN = 5V; CIN = 1F TA = 25C unless noted, bold values indicate -40C TA +85C. Symbol Internal Switch RDS(ON) On Resistance VIN = 5V, IOUT = 100mA Switch = OFF, VOUT = 0V Active Low Enable, VEN = 1.5V Active High Enable, VEN = 0V 170 220 275 0.1 10 m m A Parameter Condition Min. Typ. Max. Units
ILEAK
Output Leakage Current
Output Current Limit (MIC2095) ILIMIT Fixed Current Limit VOUT = 0.8 x VIN 0.5 0.7 0.9 A
Output Current Limit (MIC2098) ILIMIT Fixed Current Limit VOUT = 0.8 x VIN 0.9 1.1 1.5 A
Output Current Limit (MIC2097, MIC2099) IOUT = 1.1A, VOUT = 0.8 x VIN; VIN =2.5V CLF Variable Current Limit Factors IOUT = 0.5A, VOUT = 0.8 x VIN; VIN =2.5V IOUT = 0.2A, VOUT = 0.8 x VIN; VIN =2.5V IOUT = 0.1A, VOUT = 0.8 x VIN; VIN =2.5V Kickstart ILIMIT_2nd tD_LIMIT Fault Flag VFAULT/ Fault Flag Output Voltage Fault Flag Off Current IOL = 10mA VFAULT/ =5V 0.25 0.01 0.4 1 V A
TM
175 152 138 121
215 206 200 192
263 263 263 263
V V V V
Current Limit (MIC2097) Secondary Current Limit Duration of Kickstart Current Limit
TM
VIN = 2.5V; VOUT = 0V VIN = 2.5V 77
1.5 105 192
A ms
Fault Delay (MIC2095, MIC2098, MIC2099) tD_FAULT Delay before asserting or releasing FAULT/ Time from current limiting (VOUT = 0.4 x VIN) to FAULT/ state change 20 32 49 ms
Fault Delay (MIC2097) tD_FAULT Delay before asserting or releasing FAULT/ Time from current limiting (VOUT = 0.8 x VIN) to FAULT/ state change; VIN = 2.5V 77 105 192 ms
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. Specifications for packaged product only. 5. Check the Ordering Information section to determine which parts are Active High or Active Low. 6. Requires proper thermal mounting to achieve this performance.
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Timing Diagrams
tRISE 90% 10% 90% 10% tFALL
Rise and Fall Times
ENABLE
50% tON_DLY
50% tOFF_DLY 90%
VOUT 10%
Switching Delay Times
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Typical Characteristics
VIN Shutdown Current vs. Input Voltage
10 SUPPLY CURRENT (A) SUPPLY CURRENT (A) 8 6 4
-2 Version
VIN Shutdown Current vs. Input Voltage
6 SUPPLY CURRENT (A) 100 80 60 40 20 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 2.5 3.0
VIN Supply Current vs. Input Voltage
4
2
2 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V)
0
-1 Version
-2 INPUT VOLTAGE (V)
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
Current Limit vs. Input Voltage MIC2097/MIC2099
1.2 1.0
Current Limit vs. Input Voltage MIC2095
1.0 0.8 0.6
ISC ILIMIT
Current Limit vs. Input Voltage MIC2098
1.2 1.0 CURRENT LIMIT (A) 0.8
ISC ILIMIT
0.8 0.6 0.4
VOUT=0.8*VIN RSET = 298, ISET = 0.7A RSET = 508, ISET = 0.4A
CURRENT LIMIT (A)
CURRENT LIMIT (A)
RSET = 200, ISET = 1.08A
0.6 0.4 0.2 0.0
VOUT = 0.8*VIN
0.4 0.2 0.0
0.2 0.0 2.5 3.0 3.5
RSET = 1920, ISET=0.1A
VOUT = 0.8*VIN
4.0
4.5
5.0
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Current Limit vs. Input Voltage MIC2097/MIC2099
1.2 1.0 CURRENT LIMIT (A) 0.8 0.6 0.4 0.2 0.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V)
ISC RSET =195 ISET = 1.1A VOUT = 0.8*VIN
Switch On Resistance vs. Input Voltage
240 220 RESISTANCE (m) 40 35 30 DELAY (ms) 25 20 15 10
IOUT = 100mA
Fault Delay vs. Input Voltage MIC2095/MIC2098/MIC2099
ILIMIT
200 180 160 140 120 100 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V)
CLOAD = 1F RLOAD = 100
5 0 2.5 3.0 3.5 4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
Fault Delay vs. Input Voltage MIC2097
140 PEAK CURRENT (A) 120 100 DELAY (ms) 80 60 40 20 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V)
CLOAD = 1F RLOAD = 100
Kickstart Current vs. Input Voltage MIC2097
1.8 1.6 1.4 1.2
TIME (ms) 120 100 80 60 40 20 140
Kickstart Period vs. Input Voltage MIC2097
1.0 0.8 0.6 0.4 0.2 0.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V)
RSET = 195 ISET = 1.1A VOUT = 0.8*VIN
0 2.5 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) 5.5
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Typical Characteristics (Continued)
VIN ShutdownCurrent vs. Temperature
1.0 SHUTDOWN CURRENT (A)
-1 Version
VIN ShutdownCurrent vs. Temperature
10.0
-2 Version
VIN Supply Current vs.Temperature
100
VIN = 5V
SUPPLY CURRENT (A)
0.8 0.6 0.4 0.2
VIN = 5V
8.0 6.0 4.0
VIN = 3V VIN = 5V
SUPPLY CURRENT (A)
80 60 40 20 0
VIN = 3V
VIN = 3V
2.0 0.0
0.0 -40 -15 10 35 60 85 TEMPERATURE (C)
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (C)
TEMPERATURE (C)
1.0 0.8 0.6 0.4 0.2 0.0 -40
Current Limit vs. Temperature MIC2095
ILIMIT
1.2 CURRENT LIMIT (A) 1.0 0.8 0.6 0.4 0.2 0.0 -40
Current Limit vs. Temperature MIC2098
1.2 1.0 CURRENT LIMIT (A)
Current Limit vs.Temperature MIC2097/MIC2099
CURRENT LIMIT (A)
ITHRESHOLD
ILIMIT
0.8 0.6
ISC
ISC VIN = 5.0V VOUT = 4V
0.4 0.2
VIN = 5.0V VOUT = 4V RSET =195 ISET = 1.1A
ISC
VIN = 5.0V VOUT = 4V
-15
10
35
60
85
0.0 -40 -15 10 35 60 85 TEMPERATURE (C)
-15
10
35
60
85
TEMPERATURE (C)
TEMPERATURE (C)
240 220 RESISTANCE (m) 200 180 160 140 120 100 -40 -15
RDS(ON) vs. Temperature
VIN = 3.3V
Output Fall Time vs. Temperature
340 300 FALL TIME (s) 260 220 180 140 100
CLOAD = 1F RLOAD =100 VIN = 3V VIN = 5.0V
1200 1000 RISE TIME (s) 800 600 400 200 0 -40 -15 10 35 60 85 -40 -15
Output Rise Time vs. Temperature
VIN = 5.0V
VIN = 3V
VIN = 5.0V
CLOAD = 1F RLOAD =100
10
35
60
85
10
35
60
85
TEMPERATURE (C)
TEMPERATURE (C)
TEMPERATURE (C)
2.5 VIN ULVO THRESHOLDS (V) 2.4
VIN UVLO Thresholds vs. Temperature
40 35
Fault Delay vs. Temperature MIC2095/MIC2099
VIN = 5.0V
Kickstart Current vs. Temperature MIC2097
1.60 1.55 PEAK CURRENT (A) 1.50 1.45 1.40 1.35 1.30 1.25 1.20 85 -40 -15 10 35
VOUT = 4V RSET =195 ISET = 1.1A VIN = 5.0V VIN = 3V
VIN Rising
30 Delay (ms) 25 20 15 10 5
CLOAD = 1F RLOAD =100 VIN = 3V
2.3 2.2 2.1 2.0 -40 -15 10 35 60 85 TEMPERATURE (C)
VIN Falling
0 -40 -15 10 35 60 TEMPERATURE (C)
60
85
TEMPERATURE (C)
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Typical Characteristics (Continued)
Kickstart Period vs. Temperature MIC2097
VIN = 5.0V
ILIMIT & ISET vs. RSET MIC2097/MIC2099
1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 250 200 VIN - VOUT (mV)
ISET
VIN - VOUT (VIN = 5.0V) vs. Output Current
85C 25C
160 140 120 TIME (ms)
80 60 40 20 0 -40 -15
VIN = 3V
ISET (A)
100
150 100 50
-40C
ILIMIT
VIN = 5V Vo=4V TA = 25C
VIN = 5V
0 300 600 900 1200 1500 1800 2100 R SET() 0.0 0.2 0.4 0.6 0.8 1.0 1.2 OUTPUT CURRENT (A)
10
35
60
85
TEMPERATURE (C)
VIN - VOUT (VIN = 3.0V) vs. Output Current
250 200 VIN - VOUT (mV) 150 100
VIN = 3V 85C 25C -40C
50 0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 OUTPUT CURRENT (A)
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Functional Characteristics
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Functional Characteristics (Continued)
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Functional Characteristics (Continued)
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Functional Characteristics (Continued)
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Functional Characteristics (Continued)
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Functional Diagram
MIC2095/97/98/99 Functional Diagram
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MIC2095/97/98/99 Limitations on COUT The part may enter current limit when turning on with a large output capacitance. This 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 the following equation:
ILIMIT _ MIN x t D _ FAULT _ MIN VIN _ MAX
Functional Description and Application Information
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. 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 micro amps. 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. When the switch is enabled, current can flow both ways, from VIN to VOUT, or VOUT to VIN. CIN A minimum 1F bypass capacitor positioned as close as possible 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 a good quality, low-ESR ceramic capacitor is recommended. An additional 22F (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 3 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 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 0.1F to 1F are recommended. Again, good quality, low-ESR capacitors, preferably ceramic, should be chosen. COUT An output capacitor is recommended to reduce ringing and voltage sag on the output during a transient condition. A value between 1f and 10f is recommended, however, larger values can be used.
C OUT _ MAX =
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 current limiting switches protect 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 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 switch goes into thermal shutdown. KickstartTM The MIC2097 has a Kickstart feature that allows higher momentary current surges before the onset of current limiting. This permits dynamic loads, such as small disk drives or portable printers to draw the inrush current needed to overcome inertial loads without sacrificing system safety. The Kickstart parts differ from the nonKickstart parts which more rapidly limit load current, potentially starving a motor and causing the appliance to stall or stutter. During the Kickstart delay period, (typically 105ms), a secondary current limit (nominally set at 1.5A), is in effect. If the load demands a current in excess the secondary limit, Kickstart parts act immediately to restrict output current to the secondary limit for the duration of the Kickstart period. After this time the Kickstart parts revert to their normal current limit. An example of Kickstart operation is in Figure 1. Kickstart may be over-ridden by the thermal protection circuit and if sufficient internal heating occurs, Kickstart will be terminated and the output switch will be turned off. After the parts cools, if the load is still present IOUT ILIMIT, not ILIMIT_2nd.
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MIC2095/97/98/99 pull-up resistor. FAULT/ may be tied to a pull-up voltage source which is less than or equal to VIN. Soft-Start Control Large capacitive loads can create significant inrush current surges when charged through the current limiting switch. When the switch is enabled, the built-in soft-start limits the initial inrush current by slowly turning on the output. Power Dissipation and Thermal Shutdown Thermal shutdown is used to protect the current limiting 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 145C (typical). The switch 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 switch will continue cycling between ON and OFF states until the reason for the overcurrent condition has been resolved. Depending on 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 the following equation:
PD = R DS(ON) x (IOUT )
2
Figure 1. MIC2097 Kickstart Operation
Figure 1 Label Key: A. The MIC2097 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. 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 = 0V. Limiting response will be the same for dead shorts). F. Thermal shutdown followed by thermal cycling. G. Excessive load released, normal load remains. MIC2097 drops out of current limiting. H. FAULT/ delay period followed by FAULT/ going HIGH. Enable Input The ENABLE pin is a logic level compatible input which turns on or off the main MOSFET switch. There are two versions of each device. The -1 version has an active high (ENABLE) and the -2 version has an active low (ENABLE/). Fault Output The FAULT/ is an N-channel open-drain output, which is asserted (LOW true) when the device either begins current limiting or enters thermal shutdown. The FAULT/ signal asserts after a brief delay period in order to filter out very brief over current conditions. After an overcurrent or over-temperature fault clears, the FAULT/ pin remains asserted (low) for the delay period. 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
Eq. 2
To relate this to junction temperature, the following equation can be used:
TJ = PD x R (J- A) + TA
Eq. 3
Where TJ = junction temperature, TA = ambient temperature, and R(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 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 switch will shut down and signal a fault condition. Please see the Fault Output description in the previous page for more details on the FAULT/ output. After the switch 17
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Die Temperature vs Output Current (Ambient Temperature = 85C)
MIC2095/97/98/99 For the sake of this example, the typical value of CLF at an IOUT of 1.1A is 215V. Applying Equation 5:
R LIMIT ( ) = 215V = 195 1.1A
Eq. 6
130 DIE TEMPERATURE (C) 120 110 100 90 80 70
Tamb=85C
Choose RLIMIT = 196 (the closest standard 1% value) Designers should be aware that variations in the measured ILIMIT for a given RLIMIT resistor, will occur because of small differences between individual ICs (inherent in silicon processing) resulting in a spread of ILIMIT values. In the example above we used the typical value of CLF to calculate RLIMIT. We can determine ILIMIT's spread by using the minimum and maximum values of CLF and the calculated value of RLIMIT:
ILIMIT_MIN = 175V = 0.89 A 196 263 V = 1.34 A 196
0.0
0.2
0.4
0.6 IOUT (A)
0.8
1.0
1.2
Eq. 7
Figure 2. Die Temperature vs. IOUT
ILIMIT _ MAX =
Eq. 8
Setting ILIMIT The current limit of the MIC2097 and MIC2099 parts are user programmable and controlled by a resistor connected between the ILIMIT pin and Ground. The value of the current limit resistor is determined by the following equations:
ILIMIT = CurrentLim itFactor(CLF) R LIMIT CurrentLimitFactor(CLF) ILIMIT
Giving us a maximum ILIMIT variation of: ILIMIT_MIN 0.89A (-19%) ILIMIT_TYP 1.1A ILIMIT_MAX 1.34A (+22%)
Eq. 4
For convenience, Table 2 lists the resistance values for the RSET pin, for various current limit values.
Nominal ILIMIT
or
R LIMIT =
Eq. 5
RLIMIT
ILIMIT_MIN
ILIMIT_MAX
0.1A
1920 1000 672 508 412 344 298 263 235 213 195
0.063 0.138 0.211 0.288 0.369 0.448 0.533 0.620 0.709 0.801 0.895
0.137 0.263 0.391 0.517 0.638 0.764 0.884 1.002 1.118 1.233 1.346
The Current-Limit Factor (CLF) is a number that is characteristic to the MIC2097/9 switches. The CLF is a product of the current-setting resistor value, and the desired current-limit value. Please note that the CLF varies with the current output current, so caution is necessary to use the correct CLF value for the current that you intend to use the part at. For example: If one wishes to set a ILIMIT = 1.1A, looking in the electrical specifications we will find CLF at ILIMIT = 1.1 A, as noted in Table 1.
Min. Typ. Max. Units
0.2A 0.3A 0.4A 0.5A 0.6A 0.7A 0.8A 0.9A 1.0A 1.1A
175
215
263
V
Table 2. MIC2097 and MIC2099 RLIMIT Table
Table 1. CLF at ILIMIT = 1.1A
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Micrel, Inc. ILIMIT vs. IOUT Measured When in current limit, the switches are 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. As the (VIN - VOUT) voltage differential increases, the IC internal temperature also increases. To limit the IC's power dissipation, the current limit is reduced as a function of output voltage. This folding back of ILIMIT can be generalized by plotting ILIMIT as a function of VOUT, as shown in Figures 3 and 4. The slope of VOUT between IOUT = 0V and IOUT = ILIMIT (where ILIMIT is a normalized 1A) is determined by RON of the switch and ILIMIT.
MIC2095/97/98/99 When measuring IOUT 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 5 and 6. In Figure 5, 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 6 this test is repeated but with (VIN - VOUT) is 4V.
NORMALIZED OUTPUT CURRENT (A)
1.2 1.0 0.8 0.6 0.4 0.2 0
Normalized Output Current vs. Output Voltage (5V)
Figure 5. IOUT in Current Limiting for VOUT = 4V
0
1 2 3 4 5 OUTPUT VOLTAGE (V)
6
Figure 3. Normalized Output Current vs. Output Voltage
NORMALIZED OUTPUT CURRENT (A)
1.2 1.0 0.8 0.6 0.4 0.2 0
Normalized Output Current vs. Output Voltage (2.5V)
Figure 6. IOUT in Current Limiting for VOUT = 1V
0
0.5 1.0 1.5 2.0 2.5 OUTPUT VOLTAGE (V)
3.0
Figure 4. Normalized Output Current vs. Output Voltage
Under Voltage Lock Out (UVLO) The switches have an Under Voltage Lock Out (UVLO) feature that will shut down the switch in a reproducible manner 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 turnoff. While disable by the UVLO circuit, the output switch (power MOSFET) is OFF and no circuit functions, such as FAULT/ or ENABLE, are considered to be valid or operative.
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MIC2095/97/98/99
Typical Application Schematics
Figure 7. MIC2095-1 or MIC2098-1 Typical Schematic
Note: MIC2095-1 and MIC2098-1; R5=NF; EN pin uses R4 (pull-up resistor to VIN) to enable the output without an external enable signal. MIC2095-2 and MIC2098-2; R4=NF; EN/ pin uses R5 (pull-down resistor to GND) to enable the output without an external enable signal.
Figure 8. MIC2097-1 Typical Schematic
Note: MIC2097-1; R5=NF; EN pin uses R4 (pull-up resistor to VIN) to enable the output without an external enable signal. MIC2097-2; R4=NF; EN/ pin uses R5 (pull-down resistor to GND) to enable the output without an external enable signal.
Figure 9. MIC2099-1 Schematic
Note: MIC2099-1; R5=NF; EN pin uses R4 (pull-up resistor to VIN) to enable the output without an external enable signal. MIC2099-2; R4=NF; EN/ pin uses R5 (pull-down resistor to GND) to enable the output without an external enable signal.
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MIC2095/97/98/99
Evaluation Board Schematic
Figure 10. Schematic of MIC209X Evaluation Board
Notes: 1. Evaluation board is used for all parts. 2. Part numbering scheme is 209X-Y where X is the place holder for the last number (i.e. MIC2095, MIC2097, MIC2098 or MIC2099) and Y is the polarity of the enable signal (-1 indicates active high logic and -2 indicates active low logic). 3. MIC209X-1 EN pin only requires R4 (pull-up resistor to VIN) to enable the output without an external enable signal. 4. MIC209X-2 EN/ pin only requires R3 (pull-down resistor-to-GND) to enable the output without an external enable signal. 5. R1 is NF (no fill) with the MIC2095 (fixed current limit).
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MIC2095/97/98/99
MIC209x Bill of Materials
Item Part Number Manufacturer Description Qty.
C1 C2 C3 C4 R1
(4)
08056D106MAT2A 06033D105MAT2A 0805D226MAT2A CRCW06032000FRT1 CRCW06031002FRT1
MIC2095-1YMT MIC2095-2YMT MIC2097-1YMT
AVX AVX
(1) (1)
Ceramic Capacitor, 10F, 6.3V, X5R Ceramic Capacitor, 1F, 25V, X5R Ceramic Capacitor, 22F, 6.3V, X5R 120F (optional)
(2) (2)
1 1 1 0 1 3
1 0 0
AVX(1) Vishay Dale
Resistor, 200 (0603 size), 1% Resistor, 10k (0603 size), 1%
Current-Limiting Power Distribution Switch - 0.5A Fixed Current Limit - Active High Enable Current-Limiting Power Distribution Switch - 0.5A Fixed Current Limit - Active Low Enable Current-Limiting Power Distribution Switch - Adjustable Current Limit with Kickstart - Active High Enable Current-Limiting Power Distribution Switch - Adjustable Current Limit with Kickstart - Active Low Enable Current-Limiting Power Distribution Switch - 0.9A Fixed Current Limit - Active High Enable Current-Limiting Power Distribution Switch - 0.9A Fixed Current Limit - Active Low Enable Current-Limiting Power Distribution Switch - Adjustable Current Limit - Active High Enable Current-Limiting Power Distribution Switch - Adjustable Current Limit - Active Low Enable
R2, R3, R4
U1 U1 U1
Vishay Dale
Micrel, Inc.
(3)
Micrel, Inc.(3) Micrel, Inc.(3)
U1 U1 U1 U1 U1
Notes: 1. AVX: www.avx.com.
MIC2097-2YMT MIC2098-1YMT MIC2098-2YMT MIC2099-1YMT MIC2099-2YMT
Micrel, Inc.(3) Micrel, Inc.(3) Micrel, Inc.(3) Micrel, Inc.(3) Micrel, Inc.(3)
0 0 0 0 0
2. Vishay: www.vishay.com. 3. Micrel, Inc.: www.micrel.com. 4. May be omitted when used with the MIC2095 or MIC2098 (fixed current limit).
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MIC2095/97/98/99
PCB Layout Recommendations
Figure 11. MIC209X Evaluation Board Top Layer
Figure 12. MIC209X Evaluation Board Bottom Layer
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MIC2095/97/98/99
Package Information
6-Pin 1.6mm x 1.6mm TMLF (MT)
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MIC2095/97/98/99
Recommended Landing Pattern
6-Pin 1.6mm x 1.6mm TMLF (MT)
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) 2010 Micrel, Incorporated.
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