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MIC2544A/2548A
Programmable Current Limit High-Side Switch
General Description
The MIC2544A and MIC2548A are integrated, high-side power switches optimized for low loss DC power switching and other power management applications, including Advanced Configuration and Power Interface (ACPI). The MIC2544A/48A is a cost-effective, highly integrated solution that requires few external components to satisfy USB and ACPI requirements. Load current management features include a precision resistor-programmable output current-limit and a soft-start circuit which minimizes inrush current when the switch is enabled. Thermal shutdown, along with current-limit, protects the switch and the attached device. The MIC2544A/48A's open-drain flag output is used to indicate current-limiting or thermal shutdown to a local controller. The MIC2548A has an additional internal latch which turns the output off upon thermal shutdown providing robust fault control. The enable signal is compatible with both 3V and 5V logic, and is also used as the thermal shutdown latch reset for the MIC2548A The MIC2544A and MIC2548A are available in active-high and active-low enable versions in the 8-pin SOIC (small-outline integrated circuit) and 8-pin MSOP (microsmall-outline package).
Features
* * * * * * * * * * * 2.7V to 5.5V input Adjustable current-limit up to 1.5A Reverse current flow blocking (no "body diode") 90A typical on-state supply current 1A typical off-state supply current 120m maximum on-resistance Open-drain fault flag Thermal shutdown Thermal shutdown output latch (MIC2548A) 2ms (slow) turn-on and fast turn-off Available with active-high or active-low enable
Applications
* * * * * * USB power distribution PCI bus power switching Notebook PC ACPI power distribution PC card hot swap applications Inrush current-limiting
_________________________________________________________________________________________________________
Typical Application
Typical Advanced Configuration and Power Interface (ACPI) Application
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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Micrel, Inc.
MIC2544A/2548A
Ordering Information*
Part Number MIC2544A-1YM MIC2544A-1YMM MIC2544A-2YM MIC2544A-2YMM MIC2548A-1YM MIC2548A-1YMM MIC2548A-2YM MIC2548A-2YMM Enable Active High Active High Active Low Active Low Active High Active High Active Low Active Low Latch* Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package 8-pin SOIC 8-pin MSOP 8-pin SOIC 8-pin MSOP 8-pin SOIC 8-pin MSOP 8-pin SOIC 8-pin MSOP Pb-Free
*Thermal Shutdown Latch
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Pin Configuration
8-pin SOIC
8-Pin MSOP (MM)
Note: 1. Pins 4 and 5 for SOIC and MSOP are different.
Pin Description
Pin Number MSOP-8 1 Pin Number SOIC-8 1 Pin Name EN Pin Function Enable (Input): Logic-compatible enable input. Active-high (-1) or activelow (-2). High input >1.7V typical; low input <1.5V typical. Do not float. MIC2548A only: Also resets thermal shutdown latch. Fault Flag (Output): Active-low, open-drain output. Indicates over current or thermal shutdown conditions. MIC2548A only: latched low on thermal shutdown. Ground. Current Limit: Sets current-limit threshold using an external resistor, RSET1 connected to ground. 154 < RSET < 2.29k. Input: Output MOSFET drain. Also powers internal circuitry. Switch (Output): Output MOSFET source. Pins 6 and 8 must be externally connected. Not internally connected.
2 3 5 7 6,8 4
2 3 4 7 6,8 5
FLG GND ILIM IN OUT NC
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Absolute Maximum Ratings(1)
Supply Voltage (VIN) ....................................... -0.3V to 6.0V Output Voltage (VOUT) ....................................... -0.3V to VIN Output Current (IOUT) .................................Internally Limited Enable Input (VEN) ................................... -0.3V to VIN+0.3V Fault Flag Voltage (VFLG)................................... -0.3V to 6V Fault Flag Current (IFLG) ..............................................50mA Storage Temperature (Ts) .........................-65C to +150C Junction Temperature (TJ) ........................Internally Limited Lead Temperature (soldering, 10 sec.)...................... 260C ESD Rating(3) .................................................................. 2kV
Operating Ratings(2)
Supply Voltage (VIN)..................................... +2.7V to +5.5V Enable Voltage (VEN).............................................. 0V to VIN Current Limit Set Range................................... 0.1A to 1.5A Ambient Temperature (TA) .......................... -40C to +85C Package Thermal Resistance SOIC (JA) ........................................................160C/W MSOP (JA) ......................................................206C/W
Electrical Characteristics
VIN = +5V; TA = 25C, Bold values indicate -40C to +85C, unless noted.
Parameter Condition Min Typ Max Units
Power Input Supply
Input Voltage Range (VIN) Shutdown Current Supply Current Switch off, VOUT = Open Switch on, VOUT = Open
(4) (4)
2.7 0.75 90
5.5 5 160
V A A
Enable Input
EN Logic Level High EN Logic Level Low En Bias Current EN Input Capacitance EN Pulse Reset Width VIN to EN Set-Up VEN = 2.4V VEN = 0.8V (Note 5) MIC2548 Thermal Shutdown Latch MIC2548
(5) (5) (4) (4)
2.4
1.7 1.5 0.1 0.1 1 0.8 1.0 1.0
V V A A pF s s
5 0
Internal Switch
On Resistance RDS(ON) Output Leakage Current IOUT = 500mA Switch off 80 1 120 10 m A
Current Limit
Current Limit Factor IOUT = 100mA to 500mA, VOUT = 1V to 4V(6) IOUT = 500mA to 1.5A, VOUT = 1V to 4V Current-Limit Response Time VOUT = 0V(5) (6)
(6)
161 184
230 230 25
299 276
V V s
Output Response Times
Output Turn-On Delay Output Turn-On Rise Time Output Turn-Off Delay Output Turn-Off Fall Time RL = 10, CL = 1F, Figures 1a, 1b RL = 10, CL = 1F, Figures 1a, 1b RL = 10, CL = 1F, Figures 1a, 1b RL = 10, CL = 1F, Figures 1a, 1b 1 1 2 2 30 30 5 5 ms ms s s
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Error Flag Output Resistance Error Flag Off Current VIN = 5V, IL = 10A VIN = 3.3V, IL = 10A VFLG = 5.0V 7 9 0.01 15 20 1
MIC2544A/2548A
A
Thermal Protection
Over-temperature Shutdown Over-temperature Shutdown Hysteresis
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. Off is 0.8V and on is 2.4V for the MIC2544A-1 and MIC2548A-1. Off is 2.4V and on is 0.8V for the MIC2544A-2 and MIC2548A-2. The enable input has about 200mV of hysteresis. 5. Guaranteed by design but not production tested. 6. Current limit threshold is determined by ILIMIT = 230V , where RSET is in ohms. RSET
TJ Rising
150 5
C C
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Test Circuit
Functional Characteristics Test Circuit
Timing Diagrams
Figure 1a. MIC2544A-1/MIC2548A-1
Figure 1b. MIC2544A-2/MIC2548A-2
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Timing Diagrams (Continued)
Figure 2a. MIC2548A-2 Timing: Output is reset by toggling EN
Figure 2b. MIC2544A-2 Timing
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Typical Characteristics
1.0 SHUTDOWN CURREN T (A) 0.8 0.6 0.4
40C
Shutdown Current vs. Input Voltage
SUPPLY CURRENT (A)
120 100
25C
Supply Current vs. Input Voltage
-40C
2.0 ENABLE THRESHOLD (V) 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 2.5 3
Enable Threshold vs. Input Voltage
Rising
80 60 40 20 0
85C
Falling
0.2 0.0
85C
25C
Hysteresis
2.5
3
3.5
4
4.5
5
5.5
2.5
3
3.5
4
4.5
5
5.5
3.5
4
4.5
5
5.5
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
2.0
Current Limit vs. Input Voltage
SHORT CIRCUIT CURRENT (A)
-40C
1.6 1.4 1.2
Short Circuit Current vs. Input Voltage
-40C 85C
120 100 RDS(ON) (m) 80
RDS(ON) vs. Input Voltage
85C
CURRENT LIMIT (A)
1.5
25C 85C
1.0 0.8 0.6 0.4 0.2 0.0 2.5
25C
25C
1.0
60
-40C
40 20 0
0.5
0.0 2.5 3 3.5 4 4.5 5 5.5 INPUT VOLTAGE (V)
3
3.5
4
4.5
5
5.5
2.5
3
3.5
4
4.5
5
5.5
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
1.0 SHUTDOWN CURRENT (A) 0.8 0.6 0.4 0.2 0.0 -40
5V
Shutdown Current vs. Temperature
SUPPLY CURRENT (A)
90 80 70 60 50 40 30 20 10 0 85 -40
Supply Current vs. Temperature
ENABLE THRESHOLD (V)
2.5 2.0 1.5
Enable Threshold vs. Temperature
5V
Rising
3.3V
Falling
1.0 0.5 0.0
Hysteresis
3.3V
-15
10
35
60
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (C)
TEMPERATURE (C)
TEMPERATURE (C)
2.0
Current Limit vs. Temperature
SHORT CIRCUIT CURRENT (A)
5V
2.0
Short Circuit Current vs. Temperature
100 90 80
RDS(ON) vs. Temperature
5V
CURRENT LIMIT (A)
1.5
3.3V
1.5
3.3V
RDS(ON) (m)
70 60 50 40 30 20 10 0
3.3V
1.0
1.0
5V
0.5
0.5
0.0 -40 -15 10 35 60 85 TEMPERATURE (C)
0.0 -40 -15 10 35 60 85 TEMPERATURE (C)
-40
-15
10
35
60
85
TEMPERATURE (C)
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Typical Characteristics (Continued)
3.0 UVLO THRESHOLD (V) 2.5 2.0 1.5 1.0 0.5 0.0 -40 -15 10 35 60 85 TEMPERATURE (C)
Hysteresis
UVLO Threshold vs. Temperature
160
UTH
VIN - VOUT vs. Output Current
160 140
VIN - VOUT vs. Output Current
85
140 VIN - VOUT (mV)
85 25
VIN - VOUT (mV)
120 100 80 60 40 20 0 0
V IN = 5V
120 100 80 60 40 20 0 0
VIN = 3.3V
LTH
25
-40
-40
0.25
0.5
0.75
1
1.25
1.5
0.25
0.5
0.75
1
1.25
1.5
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
2500 2000 RSET () 1500
RSET () vs. Output Current
OUTPUT CURRENT (A)
1.6 1.4 1.2
Output Current vs. RSET
6 5 Rise Time (ms) 4 3 2 1
Rise Time vs. Input Voltage
-40C
1.0 0.8 0.6 0.4 0.2
I_OUT_Mea I_OUT
25C 85C
RSET = 230
1000 500 0 0 0.25 0.5 0.75 1
ILIMIT
0.0 1.25 1.5 0 500 1000 1500 2000 2500 OUTPUT CURRENT (A) RSET ()
0 2.5 3 3.5 4 4.5 5 5.5 INPUT VOLTAGE (V)
140 120
Fall Time vs. Input Voltage
-40C
4.5 4.0 3.5 RISE TIME (ms) 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -40
5V
Rise Time vs. Temperature
3.3V
140 120 FALL TIME (us) 100 80 60 40 20 0
Fall Time vs. Temperature
3.3V
FALL TIME (us)
100 80 60 40 20 0 2.5 3 3.5 4
85C
25C
5V
4.5
5
5.5
-15
10
35
60
85
-40
-15
10
35
60
85
INPUT VOLTAGE (V)
TEMPERATURE (C)
TEMPERATURE (C)
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Functional Characteristics
Note: The following applies unless otherwise noted: MIC2544A-1, TA = 25C, VIN = 5.0V, RSET = 232, COUT = 10F.
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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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Block Diagram
Functional Description
The MIC2544A and MIC2548A are high-side N-channel switches available with either active-high or active-low enable inputs. Fault conditions turn-off or inhibit turn-on of the output transistor and activate the open-drain error flag transistor making it sink current-to-ground. Input and Output IN is the power supply connection to the logic circuitry and the drain of the output MOSFET. OUT is the source of the output MOSFET. In a typical circuit, current flows from IN to OUT toward the load. If VOUT is greater than VIN, current will flow from OUT to IN since the switch is bidirectional when enabled. The output MOSFET and driver circuitry are also designed to allow the MOSFET source to be externally forced to a higher voltage than the drain (VOUT > VIN) when the switch is disabled. In this situation, the MIC2544A/48A avoids undesirable current flow from OUT to IN. Both OUT pins must be connected together. Thermal Shutdown Thermal shutdown shuts off the output MOSFET and signals the fault flag if the die temperature exceeds 150C. 5C of hysteresis prevents the switch from turning on until the die temperature drops to 145C. Over-temperature detection functions only when the
switch is enabled. The MIC2548A features an internal latch which causes the part to remain off after thermal shutdown until a reset pulse is provided via the enable pin (pin 1). While in current-limit, the thermal shutdown latch prevents on/off cycling of the output. Refer to Figures 2a and 2b for timing diagram. The flag remains low until reset. Enable Input EN must be driven logic high or logic low, or be pulled high or low for a clearly defined input. Floating the input may cause unpredictable operation. EN should not be allowed to go negative with respect to GND, and VEN should be less than or equal to VIN.
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Micrel, Inc. Setting ILIMIT The MIC2544A/2548A'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:
I LIMIT = CurrentLimitFactor(CLF) R SET I_OUT R_SET I_OUT_Min
MIC2544A/2548A Giving one a maximum ILIMIT variation over-temperature of: ILIMIT_MIN ILIMIT_TYP ILIMIT_MAX 0.79A (-21%) 1.0A 1.19A (+19%)
or
R SET = CurrentLim itFactor(V) ILIMIT (A)
I_OUT_Max
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5
1150 767 575 460 383 329 288 256 230 209 192 177 164 153
0.140 0.210 0.280 0.350 0.480 0.560 0.640 0.720 0.800 0.880 0.960 1.040 1.120 1.200
0.260 0.390 0.520 0.650 0.720 0.840 0.960 1.080 1.200 1.320 1.440 1.560 1.680 1.800
For example: Set ILIMIT = 1.0A Looking in the Electrical specifications we will find CLF at ILIMIT = 1 A.
Min 184 Typ 230 Max 276 Units V
Table 1. CLF at ILIMIT = 1A
For the sake of this example, we will say the typical value of CLF at an IOUT of 1A is 230V. Applying the equation above:
R SET ( ) = 230V = 230 1.0A
RSET = 232 (the closest standard 1% value) 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 a typical value of CLF was used to calculate RSET. One can determine ILIMIT's spread by using the minimum and maximum values of CLF and the calculated value of RSET.
ILIMIT_MIN = 184V = 0.79 A 232 276V = 1.19 A 232
Table 2. MIC2544A/2548A RSET Table
Short-Circuit Protection In the event of a short circuit, the output current will fold back to approximately 70% of the short-circuit currentlimit. Fault Flag FLG is an N-channel, open-drain MOSFET output. The fault flag is active (low) for current-limit or thermal shutdown conditions. The flag output MOSFET is capable of sinking a 10mA load to typically 100mV above ground. The FLG response delay time tD is typically 5s.
ILIMIT _ MAX =
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Application Information
Supply Filtering A minimum 1F bypass capacitor from IN-to-GND, located near the MIC2544A and MIC2548A, is strongly recommended to control supply transients. Without a bypass capacitor, an output short may cause sufficient ringing on the input (from supply lead inductance) to damage internal control circuitry. An additional 22F input capacitor placed close to the IC is required if a bulk input capacitor is further than 3 inches away from the IC. Input transients must not exceed the absolute maximum supply voltage (VIN max = 6V) even for a short duration.
Figure 4. Flag Glitch with COUT = 120F
Adding an optional series resistor-capacitor (RSET2), in parallel with RSET, and as shown in Figure 8, allows the transient current-limit to be set to a different value than steady-state. A typical USB hot-plug inrush is 2A to 3A for 10s to 20s. If RSET is 309 (525mA), an RSET2 of 100 (2.3A) and CSET of 1F (RC = 100s) allows transient surge of 3A to pass for 100s without tripping the over current flag (FLG), as shown in Figure 5.
Figure 3. Supply Bypassing
Power Dissipation The device's junction temperature depends upon several factors such as the load, PCB layout, ambient temperature, and package type. Equations that can be used to calculate power dissipation and junction temperature are found below. Calculation of power dissipation can be accomplished by the following equation: PD = RDS(on) x (IOUT)2 To relate this to junction temperature, the following equation can be used: Tj = PD x JA + TA where: Tj = junction temperature TA = ambient temperature JA = is the thermal resistance of the package Transient Over Current Filter The inrush current from the connection of a heavy capacitive load may cause the fault flag to fall for 10s to 200s while the switch is in a constant-current mode, charging the capacitance, as shown in Figure 4.
Figure 5. ILIMIT Filter with COUT = 120F
Figure 6 circuit can also be used to filter out transient FLG assertion. The value of the RC time constant should be selected to match the length of transient. Figure 7 shows the FLAG pin waveform due to the inrush of current surge.
Figure 6. Flag Filter Circuit
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Figure 7. Flag Filter with COUT = 100F
USB Power Distribution The MIC2544A is ideal for meeting USB power distribution requirements. Figure 8 depicts a USB Host application. RSET should be set to a value providing a current-limit >500mA. The accurate current-limit of the MIC2544A will reduce power supply current requirements. Also, fast reaction to short circuit faults prevent voltage droop in mobile PC applications. Printed Circuit Board Hot-Plug The MIC2544A/48A are ideal inrush current-limiters suitable for hot-plug applications. Due to the integrated charge pump, the MIC2544A/48A presents high impedance when off and slowly becomes low impedance as it turns on. This "soft start" feature effectively isolates power supplies from highly capacitive loads by reducing inrush current during hot-plug events. Figure 9 shows how the MIC2544A may be used in a hot-plug application.
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Figure 8. USB Host Application
Note: MSOP package option uses pin 5 for ILIM. Pin 4 is not connected (NC). Bold lines indicate 0.1" wide, 1-oz. copper high-current traces.
Figure 9. Hot Plug Application
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Package Information
8-pin SOIC (M)
8-Pin MSOP (MM)
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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