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MIC2007/2017
Adjustable Current Limit Power Distribution Switch
General Description
The MIC2007 and MIC2017 are current limiting, highside power switches, designed for general purpose power distribution and control in PCs, PDAs, printers and other self-powered systems. The MIC2007 and MIC2017's primary functions are current limiting and power switching. They are thermally protected and will shutdown should their internal temperature reach unsafe levels. This protects both the device and the load under high current or fault conditions. Features include: user adjustable output slew rate limiting, automatic load discharge and under voltage detection. Both devices offer user programmable current limiting thereby providing designers a continuous spectrum of current limits from 200mA to 2 Amps. The MIC2017 offers a unique new feature: KickstartTM, which allows momentary high current surges to pass unrestricted without sacrificing overall system safety. The MIC2007 and MIC2017 are excellent choices for USB and IEEE 1394 (FireWire) applications or for any system where current limiting and power control are desired. The MIC2007 and MIC2017 are offered in space saving 6-pin SOT-23 and 2mm x 2mm MLFTM packages.
Features
* 70m typical on-resistance * 2.5V - 5.5V operating range * User adjustable current limit: 0.2A - 2.0A * * * * * * KickstartTM User adjustable output slew rate control Automatic load discharge Thermal protection Under voltage lock-out Low quiescent current
Applications
* * * * * * * * USB / IEEE 1394 power distribution Desktop and laptop PCs Set top boxes Game consoles PDAs Printers Docking stations Chargers
_________________________________________________________________________________________________________
Typical Application
MIC2007 MIC2017 5V Supply VIN CSLEW USB Controller ENABLE VOUT GND ILIMIT VBUS
D+/D-
USB Port
D+/D-
USB Port
Figure 1. Typical Application Circuit
Kickstart is a trademark of Micrel, Inc MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc. Micrel Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel +1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com
October 2005
M9999-102805
Micrel
MIC2007/MIC2017
MIC2000 Family Members
Part Number Normal Limiting 2003 2004 2005 2006 2007 2008 2009 Kickstart 2013 2014 2015 2016 2017 2018 2019 Adj. Fixed I Limit I Adj. ---- Enable - Pin Function CSLEW -- -FAULT/ -- --- DLM* --- ---Load Discharge - -- ---
* Dynamic Load Management
Adj = Adjustable current limit
Fixed = Factory programmed current limit
Ordering Information
Part Number MIC2007YM6 Marking(1) FHAA No MIC2007YML
(2)
Current Limit
Kickstart
Pb-Free
Package
SOT-23-6
HAA 0.2A - 2.0A Yes
2mm X 2mm MLF
MIC2017YM6
FQAA Yes
SOT-23-6
MIC2017YML(2)
Notes:
QAA
2mm X 2mm MLF
1. Under-bar symbol ( _ ) may not be to scale. 2. Consult Factory for availability
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MIC2007/MIC2017
Pin Configuration
VOUT 1 CSLEW 2 ILIMIT 3
PAD ON BACKSIDE IS GROUND
6 VIN 5 GND 4 ENABLE
VIN 1 GND 2 ENABLE 3
6 VOUT 5 CSLEW 4 ILIMIT
6-Pin 2mm X 2mm MLF (ML) Top View
SOT 23-6 (M6)
Top View
Pin Description
Pin Number SOT-23 1 2 3 4 Pin Number MLF 6 5 4 3 Pin Name VIN GND ENABLE I LIMIT Type Description
Input -Input Input
Supply input. This pin provides power to both the output switch and the MIC2007/2017's internal control circuitry. Ground. Output enable pin. A logic HIGH activates the output switch, applying power to the load attached to VOUT. Sets the current limit threshold via a resistor connected between ILIMIT and GND. I LIMIT = Current Limiting Factor (CLF) / RSET. Slew rate control. Adding a small value capacitor between this pin and VIN slows turn-ON of the power FET. Switch output. The load being driven by MIC2007/2017 is connected to this pin.
5 6
2 1
CSLEW VOUT
Input Output
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MIC2007/MIC2017
Absolute Maximum Ratings(1)
All pins ...........................................................-0.3 to 6V Power Dissipation...............................Internally Limited Continuous Output Current.................................. 2.25A Maximum Junction Temperature ........................ 150C Storage Temperature ........................... -65C to 150C
Operating Ratings(2)
Supply Voltage............................................. 2.5V to 5.5V Continuous Output Current Range .................... 0 to 2.1A Ambient Temperature Range .................... -40C to 85C Package Thermal Resistance (JA) SOT-23-6 ....................................................230C/W MLF 2x2 mm...................................................90C/W MLF 2x2 mm JC (5) .........................................45C/W
Electrical Characteristics
VIN = 5V, TAMBIENT = 25C unless specified otherwise. Bold indicates -40C to +85C limits. Symbol
VIN IIN IIN ILEAK RDS(ON) RDSCHG CLF
Parameter
Switch Input Voltage Internal Supply Current Internal Supply Current Output Leakage Current Power Switch Resistance Load Discharge Resistance Current Limit: Factor RSET () = CLF (V) IOUT (A)
Conditions
Switch = OFF, ENABLE = 0V Switch = ON, IOUT = 0 ENABLE = 1.5V VIN = 5V, VOUT = 0 V, ENABLE = 0 VIN = 5V, IOUT = 100 mA VIN = 5V, ISINK = 5 mA IOUT = 2.0A, VOUT = 0.8VIN IOUT = 1.0A, VOUT = 0.8VIN IOUT = 0.5A, VOUT = 0.8VIN IOUT = 0.2A, VOUT = 0.8VIN MIC2017, VIN = 2.5V VIN rising VIN falling VIL(max.) VIH(min.)
Min
2.5
Typ
1 80 1.2 70
Max
5.5 5 330 10 100 125 200 286 293 298 299 6 2.5 2.4 0.5
Units
V A A A m m V V V V A V V V A C
70 210 190 168 144 2.2 2.0 1.9 1.5
126 250 243 235 225 4 2.25 2.15
ILIMIT_2nd UVLOTHRESHOLD VEN IEN OTTHRESHOLD
Secondary current limit (Kickstart) Under Voltage Lock Out threshold ENABLE Input Voltage ENABLE Input Current Over-temperature Threshold
VEN = 0V to 5.0V TJ increasing TJ decreasing
1 145 135
5
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MIC2007/MIC2017
AC Characteristics
Symbol tRISE tD_LIMIT tRESET Parameter Output turn-ON rise time Delay before current limiting Delay before resetting Kickstart current limit delay, tD_LIMIT Output Turn-on Delay Condition RL = 10, CLOAD = 1F, VOUT = 10% to 90% MIC2017 Out of current limit following a current limit event. MIC2017 RL = 43, CL = 120F, CSLEW 10pF, VEN = 50% to VOUT = 10% tOFF_DLY Output Turn-off Delay RL = 43, CL = 120F, CSLEW 10pF, VEN = 50% to VOUT = 90% 700 s 1000 1500 s 77 77 128 128 192 192 ms ms Min 500 Typ 1000 Max 1500 Units s
tON_DLY
ESD
Symbol VESD_HB VESD_MCHN Parameter Electrostatic Discharge Voltage: Human Body Model Electrostatic Discharge Voltage: Machine Model Condition VOUT and GND All other pins All pins Machine Model Min 4 2 200 Typ Max Units kV kV V
Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. Human body model: 1.5k in series with 100pF. 4. Specification for packaged product only. 5. Requires proper thermal mounting to achieve this performance.
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Timing Diagrams
ENABLE
50% tON_DLY
50% tOFF_DLY 90%
VOUT
10%
Switching Delay Times
tRISE 90% 10% 90% 10%
tFALL
Rise and Fall Times
tRISE 90%
10%
VOUT
Output Rise Time
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MIC2007/MIC2017
Typical Characteristics
100 SUPPLY CURRENT (A) 80 60 40 20 0 2
Supply Current Output Enabled
25C -40C 85C
1.00 0.90 SUPPLY CURRENT (A) 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0 2
Supply Current Output Disabled
Switch Leakage Current - OFF
1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0 -50 -30 -10 10 30 50 70 TEMPERATURE (C)
-40C 25C 85C
3 4 5 V IN (V) 6 7
(A)
3
4 VIN (V)
5
6
90
2.3 2.25 THRESHOLD (V) 2.2
UVLO Threshold vs. Temperature
V RISING RON (mOhm)
RON vs.
100 80 60 40 20 0 2 RON (mOhm)
RON vs.
120 100 80 60 40 20 5V
Supply Voltage
Temperature
3.3V 2.5V
2.15 2.1
V FALLING
2.05 -50
0 50 100 TEMPERATURE (C)
150
2.5
3
3.5 4 4.5 VIN (V)
5
5.5
0 -50 -30 -10 10 30 50 70 TEMPERATURE (C)
90
250 CURRENT LIMIT FACTOR 245 240 235 230 225 220 215 0
Current Limit Factor vs. Temperature @ 2.5V
250 CURRENT LIMIT FACTOR
85C -40C 25C
Current Limit Factor vs. Temperature @ 3V
250 25C 85C -40C CURRENT LIMIT FACTOR 245 240 235 230 225 220 215 0 245 240 235 230 225 220 215 0 0.5 1.0 1.5 CURRENT LIMIT (A) 2.0
Current Limit Factor vs. Temperature @ 5V
25C 85C -40C
0.5 1.0 1.5 CURRENT LIMIT (A)
2.0
0.5 1.0 1.5 CURRENT LIMIT (A)
2.0
250 CURRENT LIMIT FACTOR 245 240 235 230 225 220 215 0
Current Limit Factor vs. Input Voltage @ -40C
CURRENT LIMIT FACTOR
Current Limit Factor vs. Input Voltage @ 25C
250
3V
Current Limit Factor vs. Input Voltage @ 85C
250 CURRENT LIMIT FACTOR 245 240 235 230 225 220 215 0 0.5 1.0 1.5 CURRENT LIMIT (A) 2.0
2.5V
245 240 235 230 225 220 215 0 5V
5V 3V
5V
2.5V
3V
2.5V
Note: The 2.5V and 3V plots overlap.
0.5 1.0 1.5 CURRENT LIMIT (A)
2.0
0.5 1.0 1.5 CURRENT LIMIT (A)
2.0
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Functional Characteristics
Turn-On/Turn-Off
Inrush Current Response Inrush Current Inrush Current Inrush CurrentResponse Response R Inrush Current Response MIC20xx-0.5
RL CSLEW = 0pF
ENABLE (2.5V/div)
ENABLE (2.5V/div)
VIN = 5.0V RLOAD CLOAD = 100F VOUT (1V/div)
VOUT (1V/div) 0F 10F 22F47F 100F
220F
470F
IOUT (200mA/div) 0 2 4 6 8 Time (ms) 10 12 14
IOUT (200mA/div) 0 4 8 12 16 20 24 Time (ms) 28 32 36 40
Current Limit Response Thermal Shutdown
ENABLE (2.5V/div)
CSLEW Response
ENABLE (2.5V/div)
VIN = 5.0V RLOAD CLOAD = 47F VOUT (1V/div)
0pF
100pF
820pF
1800pF
2700pF 3500pF
VOUT (1V/div)
IOUT (250mA/div) 0 50 100 150 200 250 300 Time (ms) 350 400 450 500 550
IOUT (150mA/div) 0 2000 6000 10000 14000 Time (s)
VIN = 5.0V RLOAD CLOAD = 0F 18000 22000
UVLO Increasing
UVLO Decreasing
ENABLE (2.5V/div)
ENABLE (2.5V/div)
VOUT (1V/div)
VOUT (1V/div)
VIN (1/div) 0 4
Enable tied to VIN 8 12 16 20 24 28 Time (s) 32 36 40 44 48
VIN (1/div) 0
Enable tied to VIN 4 8 12 16 20 24 28 32 36 40 44 48
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MIC2007/MIC2017
Kickstart Response Normal Load with Temporary High Load
Kickstart Response No Load to Short Circuit
ENABLE (2.5V/div)
ENABLE (1V/div)
VOUT (1V/div)
VOUT (1V/div)
IOUT (0.5A/div) 0 50 100 150 200 250 300 350 Time (ms) 400 450 500 550
IOUT (0.5A/div) 0 50 100 150 200 250 300 350 Time (ms) 400 450 500 550
Kickstart Response Normal Load with Temporary Short Circuit
Kickstart Response Device Enabled into a Short Circuit
ENABLE (2.5V/div)
ENABLE (2.5V/div)
VOUT (1V/div)
VOUT (1V/div)
IOUT (0.5A/div) 0 50 100 150 200 250 300 350 Time (ms) 400 450 500 550
IOUT (0.5A/div) 0 50 100 150 200 250 300 350 Time (ms) 400 450 500 550
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MIC2007/MIC2017
Functional Diagram
Under Voltag e Detector
Current Mirror FET
Power FET
VIN
ENABLE
Control Logic and Delay Timer
Gate Control
VOUT
Thermal Sensor
CSLEW ILIMIT
Slew Rate Control
VREF Current Limit Control Loop
GND
Figure 2. MIC2007/2017 Block Diagram
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MIC2007/MIC2017 limit for the duration of the Kickstart period. After this time, the MIC2017 reverts to its normal current limit. An example of Kickstart operation is shown below.
Functional Description
Input and Output VIN is both the power supply connection for the internal circuitry driving the switch and the input (Source connection) of the power MOSFET switch. VOUT is the Drain connection of the power MOSFET and supplies power to the load. In a typical circuit, current flows from VIN to VOUT toward the load. Since the switch is bidirectional when enabled, if VOUT is greater than VIN, current will flow from VOUT to VIN. When the switch is disabled, current will not flow to the load, except for a small unavoidable leakage current of a few microamps. However, should VOUT exceed VIN by more than a diode drop (~0.6V), while the switch is disabled, current will flow from output to input via the power MOSFET's body diode. While this effect can be used to advantage when large bypass capacitors are placed on MIC2007/2017's's output, it can not be relied upon to fully or reliably discharge the load capacitance, because discharging depends upon the characteristics of the circuitry at VIN. To ensure proper discharge of any output capacitance, MIC2007/2017 is equipped with a discharge FET which is ON any time the device is not Enabled. Current Sensing and Limiting The MIC2007/2017 protects the system power supply and load from damage by continuously monitoring current through the on-chip power MOSFET. Load current is monitored, by means of a current mirror, in parallel with the power MOSFET switch. Current limiting is invoked when the load exceeds an externally set over-current 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 MIC2007/2017 goes into thermal shutdown. Kickstart (MIC2017 only) The MIC2017 is designed to allow momentary current surges (Kickstart) before the onset of current limiting, which permits dynamic loads, such as small disk drives or portable printers to draw the energy needed to overcome inertial loads without sacrificing system safety. In this respect, the MIC2017 differs markedly from MIC2007 and its peers, which immediately limit load current, potentially starving the motor and causing the appliance to stall or stutter. During this delay period, typically 128 ms, a secondary current limit is in effect. If the load demands a current in excess of the secondary limit, the MIC2017 acts immediately to restrict output current to the secondary October 2005 11
OUT
OUT
Figure 3. Kickstart Operation Picture Key: A) MIC2017 is enabled into an excessive load (slew rate limiting not visible at this time scale) The initial current surge is limited by either the overall circuit resistance and power supply compliance, or the secondary current limit, whichever is less. B) RON of the power FET increases due to internal heating (effect exaggerated for emphasis). C) Kickstart period. D) Current limiting initiated. FAULT/ goes LOW. (Note: MIC2007/2017 does not provide a FAULT/ output.) E) VOUT is non-zero (load is heavy, but not a dead short where VOUT = 0. Limiting response will be the same for dead shorts). F) Thermal shutdown followed by thermal cycling. G) Excessive load released, normal load remains. MIC2017 drops out of current limiting. H) FAULT/ delay period followed by FAULT/ going HIGH. (Note: MIC2007/2017 does not provide a FAULT/ output.) Under Voltage Lock Out Under voltage lock-out insures no anomalous operation occurs before the device's minimum input voltage of 2.5V had been achieved. Prior to reaching this voltage, the output switch (power MOSFET) is OFF and no circuit functions, such as ENABLE, are considered to be valid or operative.
M9999-102805
Micrel Enable ENABLE is a HIGH true control signal, which activates the main MOSFET switch. ENABLE will operate with logic running from supply voltages as low as 1.8V, once VIN has exceeded the UVLO threshold. ENABLE can be wire-OR'd with other MIC2007/2017s or similar devices without damage to the device. ENABLE may be driven higher than VIN, but no higher than 5.5V. Slew Rate Control Large capacitive loads can create significant current surges when charged through a high-side switch such as the MIC2007/2017. For this reason, the MIC2007/2017 provides built-in slew rate control to limit the initial inrush currents upon enabling the power MOSFET switch. Slew rate control is active upon powering up, and upon re-enabling the load. At shutdown, the discharge slew rate is controlled by the external load and output capacitor. On MIC2007/2017 slew rate is adjustable and can be
MIC2007/MIC2017 further reduced by adding an external capacitance between VIN and the CSLEW pins. Thermal Shutdown Thermal shutdown is employed to protect the MIC2007/2017 from damage should the die temperature exceed safe operating levels. Thermal shutdown shuts off the output MOSFET if the die temperature reaches 145C. The MIC2007/2017 will automatically resume operation when the die temperature cools down to 135C. If resumed operation results in reheating of the die, then another shutdown cycle will occur and the MIC2007/2017 will continue cycling between ON and OFF states until the offending load has been removed. Depending upon PCB layout, package type, ambient temperature, etc., hundreds of milliseconds may elapse from the incidence of a fault to the output MOSFET being shut off. This delay is due to thermal time constants within the system itself. In no event will the device be damaged due to thermal overload because die temperature is monitored continuously by on-chip circuitry.
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Application Information
Setting ILIMIT The MIC2007/2017's current limit is user programmable and controlled by a resistor connected between the ILIMIT pin and Ground. The value of this resistor is determined by the following equation: ILIMIT = Current Limit Factor (CLF) RSET or RSET () = Current Limit Factor (V) ILIMIT (A)
Giving us a maximum ILIMIT variation over temperature of: ILIMIT_MIN ILIMIT_TYP ILIMIT_MAX 1.12A 1.25A 1.39A or 1.25A 11% ILIMIT vs. IOUT measured The MIC2007/2017's current limiting circuitry is designed to act as a constant current source to the load. As the load tries to pull more than the allotted current, VOUT drops and the input to output voltage differential increases. When VIN -VOUT exceeds 1V, IOUT drops below ILIMIT to reduce the drain of fault current on the system's power supply and to limit internal heating of the MIC2007/2017. When measuring IOUT it is important to bear this voltage dependence in mind. Otherwise, the measurement data may appear to indicate a problem when none really exists. This voltage dependence is illustrated in Figures 4 and 5. In Figure 4, output current is measured as VOUT is pulled below VIN, with the test terminating when VOUT is 1V below VIN. Observe that once ILIMIT is reached IOUT remains constant throughout the remainder of the test. In Figure 5, this test is repeated but with VIN - VOUT exceeding 1V. When VIN - VOUT > 1V, the MIC2007/2017's current limiting circuitry responds by decreasing IOUT, as can be seen in Figure 5. In this demonstration, VOUT is being controlled and IOUT is the measured quantity. In real life applications, VOUT is determined in accordance with Ohm's law by the load and the limiting current.
Example:
Set ILIMIT = 1.25A
Looking in the Electrical specifications we will find CLF at ILIMIT = 1A. For the sake of this example, we will say the typical value of CLF at an IOUT of 1A is 235V. Applying the equation above: RSET () = 235 V 1.25 A RSET = 188 Designers should be aware that variations in the measured ILIMIT for a given RSET 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 RSET. We can determine ILIMIT's spread by using the minimum and maximum values of CLF and the calculated value of RSET. RSET = 187
(the closest standard 1% value)
ILIMIT_MIN = 210V = 1.12A 187
ILIMIT_MIN = 260V = 1.39A 187 October 2005 13
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MIC2007/MIC2017
NORMALIZED OUTPUT CURRENT (A)
1.2 1.0 0.8 0.6 0.4 0.2 0
Normalized Output Current vs. Output Voltage (5V)
0
1 2 3 4 5 OUTPUT VOLTAGE (V)
6
Figure 6. Figure 4. IOUT in Current Limiting for VIN - VOUT 1V
NORMALIZED OUTPUT CURRENT (A) 1.2 1.0 0.8 0.6 0.4 0.2 0 0 0.5 1.0 1.5 2.0 2.5 OUTPUT VOLTAGE (V) 3.0
Normalized Output Current vs. Output Voltage (2.5V)
Figure 7. CSLEW The CSLEW input is provided to increase control of the output voltage ramp at turn-on. This input allows designers the option of decreasing the output's slew rate (slowing the voltage rise) by adding an external capacitance between the pin, CSLEW, and VIN. This capacitance slows the rate at which the pass FET gate voltage increases and thus, slows both the response to an Enable command as well as VOUT's ascent to its final value. Figure 8 illustrates effect of CSLEW on turn-ON delay and output rise time.
Figure 5. IOUT in Current Limiting for VIN - VOUT >1V This folding back of ILIMIT can be generalized by plotting ILIMIT as a function of VOUT, as shown below. The slope of VOUT between IOUT = 0 and IOUT = ILIMIT (where ILIMIT = 1) is determined by RON of MIC2007/2017 and ILIMIT.
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Typical Turn-on Times vs. External C Capacitance
0.014 14 0.012 12 0.01 10 TIME (mS) 0.008 8
FAULT/
MIC2007/MIC2017 Kickstart may be over-ridden by the thermal protection circuit and if sufficient internal heating occurs, Kickstart will be terminated and IOUT 0. Upon cooling, if the ILIMIT, not IKICKSTART. load is still present IOUT
SLEW
TON TDELAY
6 0.006 4 0.004 0.002 2 0 0 0.5 1 1.5 0 2.5 0 3.5 0 4.5 000203040 TRISE
ENABLE
CSLEW (nF)
VOUT
Figure 8. CSLEW's effect on ILIMIT An unavoidable consequence of adding CSLEW capacitance is a reduction in the MIC2008/2018's ability to quickly limit current transients or surges. A sufficiently large capacitance can prevent both the primary and secondary current limits from acting in time to prevent damage to the MIC2008/2018 or the system from a short circuit fault. For this reason, the upper limit on the value of CSLEW is 4nF. Kickstart (MIC2017) Kickstart allows brief current surges to pass to the load before the onset of normal current limiting. This, in turn, permits dynamic loads to draw bursts of energy without sacrificing system safety. Functionally, Kickstart is a forced override of the normal current limiting function provided by the MIC2017. The Kickstart period is governed by an internal timer which allows current to pass unimpeded to the load for 128ms and then normal (primary) current limiting goes into action. During Kickstart a secondary current limiting circuit is monitoring output current to prevent damage to the MIC2017. This is because a hard short, combined with a robust power supply, can result in currents of many tens of amperes. This secondary current limit is nominally set at 4 Amps and reacts immediately and independently of the Kickstart period. Once the Kickstart timer has finished its count, the primary current limiting circuit takes over and holds IOUT to its programmed limit for as long as the excessive load persists. Once the MIC2017 drops out of current limiting the Kickstart timer initiates a lock-out period of 128ms such that no further bursts of current above the primary current limit, will be allowed until the lock-out period has expired. October 2005 15
Kickstart Current Limiting
IOUT
Load Removed
0
100
200
300 Time (ms)
400
500
600
Figure 9. Kickstart Operation with Varying Load Supply Filtering A 0.1F to 1F bypass capacitor positioned close to the VIN and GND pins of MIC2007/2017 is both good design practice and required for proper operation of the MIC2007/2017. This will control supply transients and ringing. Without a bypass capacitor, large current surges or an output short may cause sufficient ringing on VIN (from supply lead inductance) to cause erratic operation of the MIC2007/2017's control circuitry. Good quality, low ESR capacitors, such as Panasonic's TE or ECJ series, are suggested. When bypassing with capacitors of 10F and up, it is good practice to place a smaller value capacitor in parallel with the larger to handle the high frequency components of any line transients. Values in the range of 0.01F to 0.1F are recommended. Again, good quality, low ESR capacitors should be chosen. Power Dissipation 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 To relate this to junction temperature, the following
M9999-102805
Micrel equation can be used:
MIC2007/MIC2017
performance at higher current levels, or in higher temperature environments, thermal contact with the PCB and the exposed power paddle on the back side of the MLF package should be made. This significantly reduces the package's thermal resistance thereby extending the MIC2007/2017's operating range. It should be noted that this backside paddle is electrically active and is connected to the MIC2007/2017's GND pin.
TJ = PD x R (J- A) + TA
Where: TJ = junction temperature, TA = ambient temperature R(J-A) is the thermal resistance of the package In normal operation, the MIC2007/2017's Ron is low enough that no significant I2R heating occurs. Device heating is most often caused by a short circuit -- or very heavy load -- when a significant portion of the input supply voltage appears across the MIC2007/2017's power MOSFET. Under these conditions, the heat generated will exceed the package and PCB's ability to cool the device and thermal limiting will be invoked. In Figure 10, die temperature is plotted against IOUT assuming a constant case temperature of 85C. The plots also assume a worst case RON of 140 m at a die temperature of 135C. Under these conditions, it is clear that an SOT-23 packaged device will be on the verge of thermal shutdown (typically 145C die temperature) when operating at a load current of 1.25A. For this reason, it is recommend that MLF package be used for any MIC2007/2017 designs intending to supply continuous currents of 1A or more.
2 Vias 0.3 mm diam. to Ground Plane
1.4 mm
Die Temperature vs. Iout for Tcase = 85C
160 140
Die Temperature - C
0.8 mm
120 100 80 60 40 20 0 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 Iout - Amps
SOT-23
MLF
Figure 11. Pad for Thermal Mounting to PCB
Figure 10. Die Temperature vs. Package
Figure 10 assumes no backside contact is made to the thermal pad provided on the MLF package. For optimal
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Package Information
6-Pin SOT-23 (M6)
6-Pin 2mm X 2mm MLF (ML)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale.
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(c) 2005 Micrel, Incorporated.

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