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MIC2043-1BM [MICREL]

Single Channel, High Current, Low Voltage, Protected Power Distribution Switch; 单通道，高电流，低电压，保护配电开关
MIC2043-1BM
型号： MIC2043-1BM
厂家： MICREL SEMICONDUCTOR    MICREL SEMICONDUCTOR
描述：

Single Channel, High Current, Low Voltage, Protected Power Distribution Switch
单通道，高电流，低电压，保护配电开关

电源电路 开关 电源管理电路 光电二极管
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MIC2042/2043  
Single Channel, High Current, Low Voltage,  
Protected Power Distribution Switch  
General Description  
Features  
TheMIC2042andMIC2043arehigh-sideMOSFETswitches  
optimizedforgeneralpurposepowerdistributionapplications  
whichrequirecircuitprotection.Thedevicesswitchupto5.5V  
and as low as 0.8V while offering both programmable current  
limiting and thermal shutdown to protect the device and the  
load. A fault status output is provided in order to detect  
overcurrent and thermal shutdown fault conditions. Both  
devices employ soft-start circuitry to minimize the inrush  
current in applications that employ highly capacitive loads.  
Additionally, for tighter control over inrush current during  
start-up, the output slew-rate may be adjusted by an external  
capacitor.  
• 60mΩ max. on-resistance  
• 0.8V to 5.5V operating range  
• Adjustable current limit  
• Power-Good detection  
• Up to 3A continuous output current  
• Short-circuit protection with thermal shutdown  
• Adjustable slew-rate control  
• Circuit breaker mode (MIC2043)  
• Fault status flag  
• Undervoltage lockout  
• Output MOSFET reverse current flow block when  
disabled  
• Very fast reaction to short-circuits  
• Low quiescent current  
The MIC2043 features a auto-reset circuit breaker mode that  
latchestheoutputoffupondetectinganovercurrentcondition  
lasting more than 28ms. The output is reset by removing or  
reducing the load.  
Applications  
All support documentation can be found on Micrel’s web  
site at www.micrel.com.  
• Docking stations  
• Notebook PCs  
• PDAs  
• Hot swap board insertions  
• RAID controllers  
• USB hosts  
• ACPI power distribution  
Typical Application  
+3.3V  
C2  
0.1µF  
MIC2042-1BTS  
VOUT  
3.3V@ 1.5A  
Power  
Supply  
7
10,11,14  
13  
VBIAS  
VIN  
VOUT  
C1  
R2  
OUT1  
OUT2  
CLOAD  
33µF  
0.1µF  
294kΩ  
1%  
8, 12  
2
PGREF  
C3  
4.7µF  
R1  
20kΩ  
R3  
24.3kΩ  
1%  
LogicON/OFF  
INController  
R4  
20kΩ  
EN  
3
9
6
/FAULT  
MIC39100-2.5BS  
OVERCURRENT  
IN  
2.5V  
1
4
SLEW PWRGD  
EN  
OUT  
GND  
ILIM  
UVLOIN  
GND  
(OPEN)  
C4*  
0.022µF  
RSET  
200Ω  
5
Note:  
All VIN pins (8, 12) must be externally tied together.  
All VOUT pins (10, 11, 14) must be externally tied together.  
ILIMIT ≅ 2A.  
Output Power-Good = 3.0V.  
*C4 is optional. See "Applications Information."  
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com  
M0512-112603  
January 2005  
1
MIC2042/2043  
Micrel  
Ordering Information  
Part Number  
Standard  
Pb-Free  
Enable  
Circuit Breaker  
VBIAS  
VIN Range  
1.6V to 5.5V  
1.6V to 5.5V  
1.6V to 5.5V  
1.6V to 5.5V  
0.8V to 5.5V  
0.8V to 5.5V  
0.8V to 5.5V  
0.8V to 5.5V  
Package  
8-pin SOP  
MIC2042-1BM  
MIC2042-2BM  
MIC2043-1BM  
MIC2043-2BM  
MIC2042-1BTS  
MIC2042-2BTS  
MIC2043-1BTS  
MIC2043-2BTS  
MIC2042-1YM  
MIC2042-2YM  
MIC2043-1YM  
MIC2043-2YM  
MIC2042-1YTS  
MIC2042-2YTS  
MIC2043-1YTS  
MIC2043-2YTS  
Active High  
Active Low  
Active High  
Active Low  
Active High  
Active Low  
Active High  
Active Low  
8-pin SOP  
X
X
8-pin SOP  
8-pin SOP  
X
X
X
X
14-pin TSSOP  
14-pin TSSOP  
14-pin TSSOP  
14-pin TSSOP  
X
X
Pin Configuration  
PWRGD  
1
2
3
4
5
6
7
14 VOUT  
13 PGREF  
12 VIN  
EN  
/FAULT  
GND  
1
2
3
4
8
7
6
5
VOUT  
VIN  
EN  
/FAULT  
UVLOIN  
GND  
VOUT  
VIN  
11 VOUT  
10 VOUT  
ILIM  
ILIM  
9
8
SLEW  
VIN  
8-Pin SOP (M)  
VBIAS  
14-Pin TSSOP (TS)  
M0512-112603  
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January 2005  
MIC2042/2043  
Micrel  
Pin Description  
Pin Number Pin Number  
8-Pin SOP 14-Pin TSSOP  
Pin Name  
EN  
Pin Function  
1
2
Switch Enable Input: Gate control pin of the output MOSFET available as an  
active high (–1) or active low (–2) input signal.  
2
3
/FAULT  
Fault Status Output: Open-drain N-Channel device, active low. This pin  
indicates an overcurrent or thermal shutdown condition. For an overcurrent  
event, /FAULT is asserted if the duration of the overcurrent condition lasts  
longer than 28ms.  
3
5
9
GND  
Ground Connection: Tie to analog ground.  
N/A  
SLEW  
Slew-Rate Control Input: A capacitor connected between this pin and ground  
will reduce (slow) the output slew-rate. The output turn-on time must be less  
than the nominal flag delay of 28ms in order to avoid nuisance tripping of the  
/FAULT output since VOUT must be “fully on” (i.e., within 200mV of the voltage  
at the input) before the /FAULT signal delay elapses. The capacitor requires a  
16V rating, or greater, 25V is recommended. See “Applications Information,”  
“Output Slew-Rate Adjustment” for further detail.  
4
6
ILIM  
VIN  
Current Limit Set: A resistor, RSET, connected to this pin sets the current  
limit threshold as CLF/RSET, where CLF is the current limit factor specified in  
the “Electrical Characteristics” table. For the MIC2042/43, the continuous  
output current range is 0.5A to 3A.  
5,7  
8,12  
Switch Input Supply: The drain of the output MOSFET. The range of input for  
the switch is 0.8V to 5.5V. These pins must be externally connected together  
to achieve rated performance.  
6,8  
10,11,14  
7
VOUT  
VBIAS  
Switch Output: The source of the output MOSFET. These pins must be  
externally connected together to achieve rated performance.  
N/A  
Bias Supply Input: This input pin supplies power to operate the switch and  
internal circuitry. The input range for VBIAS is 1.6V to 5.5V. When switched  
voltage (VIN) is between 1.6V to 5.5V and the use of a single supply is desired,  
connect VBIAS to VIN externally.  
N/A  
13  
PGREF  
Power-Good Threshold (Input): Analog reference used to specify the  
PWRGD threshold. When the voltage at this pin exceeds its threshold, VTH  
PWRGD is asserted high. An external resistive divider network is used to  
determine the output voltage level at which VTH is exceeded. See  
“Functional Description” for further detail. When the PWRGD signal is not  
utilized, this input should be tied to VOUT.  
,
N/A  
N/A  
1
4
PWRGD  
UVLOIN  
Power-Good Output: Active high, open-drain. This pin asserts high when the  
voltage at PGREF exceeds its threshold.  
Undervoltage Lockout Adjust Input: With this pin left open, the UVLO  
threshold is internally set to 1.45V. When the switching voltage (V ) is below  
IN  
1.6V, connecting an external resistive divider to this input will lower the  
UVLO threshold. The total resistance of the divider must be less than  
200kΩ. See “Applications Information” for further detail.  
January 2005  
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M0512-112603  
MIC2042/2043  
Micrel  
Absolute Maximum Ratings(1)  
Operating Ratings(2)  
Supply Voltage  
Supply Voltage  
V
and V  
............................................................................. 6V  
V
............................................................... 0.8V to 5.5V  
IN  
BIAS  
IN  
/FAULT, PWRGD Output Voltage ...................................6V  
/FAULT, PWRGD Output Current ..............................25mA  
V
BIAS  
........................................................... 1.6V to 5.5V  
Continuous Output Current ................................ 0.5A to 3A  
Junction Temperature (T ) ...................... Internally Limited  
ESD Rating  
Ambient Temperature (T ) ........................... –40°C to 85°C  
Package Thermal Resistance  
J
A
(3)  
Human Body Model................................................... 3kV  
Machine Model ........................................................200V  
SOP (θ ) ..........................................................160°C/W  
JA  
TSSOP (θ ) .......................................................85°C/W  
JA  
Electrical Characteristics(4)  
VIN = VBIAS = 5V; TA = 25°C unless specified otherwise. Bold indicates –40°C to +85°C.  
Symbol  
Parameter  
Condition  
IN ≤ VBIAS  
Min  
0.8  
1.6  
1.6  
Typ  
Max  
5.5  
Units  
VIN  
Switch Input Voltage  
V
14-pin TSSOP  
8-pin SOP  
V
V
V
5.5  
VBIAS  
IBIAS  
Bias Supply Voltage  
(14-pin TSSOP)  
5.5  
VBIAS Supply Current - Switch OFF No load  
VBIAS Supply Current - Switch ON  
Note 5  
0.1  
300  
5
400  
µA  
µA  
No load  
VEN  
Enable Input Voltage  
VIL(max)  
VIH(min)  
2.4  
2.5  
100  
.01  
40  
1.5  
V
V
3.5  
–1  
VENHYST  
IEN  
Enable Input Threshold Hysteresis  
Enable Input Current  
mV  
µA  
mΩ  
VEN = 0V to 5.5V  
1
RDS(ON)  
Switch Resistance  
VIN = VBIAS = 3V, 5V  
IOUT = 500mA  
60  
ILEAK  
CLF  
Output Leakage Current  
Current Limit Factor(2)  
Output off  
10  
µA  
VIN = 5V, 0.5V ≤ VOUT < 0.5VIN  
0.5A ≤ IOUT ≤ 3A  
310  
320  
205  
395  
385  
485  
A×Ω  
VIN = 3V, 0.5V ≤ VOUT < 0.5VIN  
450  
245  
A×Ω  
mV  
V
0.5A ≤ IOUT ≤ 3A  
VTH  
PGREF and UVLOIN Threshold  
Output Reset Threshold  
VIN = VBIAS = 1.6V to 5.5V  
(14-pin TSSOP)  
225  
VLATCH  
VIN = 0.8V to 5.5V  
VOUT rising (MIC2043)  
VIN–.0.2  
3
ILATCH  
VOL  
Latched Output Off Current  
Output latched off (MIC2043)  
IOL (/FAULT) = 15mA  
IOL (PWRGD) = 5mA  
VFAULT = VPWRGD = 5V  
VIN rising  
1
5
mA  
V
Output Low Voltage  
(/FAULT, PWRGD)  
0.4  
IOFF  
VUV  
/FAULT, PWRGD Off Current  
1
µA  
V
Undervoltage Lockout Threshold  
1.30  
1.20  
1.45  
1.35  
100  
1.58  
1.50  
VIN falling  
V
VUVHYST  
VUVINTH  
Undervoltage Lockout  
Threshold Hysteresis  
mV  
UVLO Adjust Pin Threshold Voltage VIN rising  
VIN falling  
205  
185  
225  
205  
20  
245  
225  
mV  
mV  
mV  
°C  
VUVINHYST  
UVLO Adjust Pin Threshold Hysteresis  
Overtemperature Threshold  
TJ increasing  
TJ decreasing  
140  
120  
°C  
M0512-112603  
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January 2005  
MIC2042/2043  
Micrel  
Symbol  
tFLAG  
tON  
Parameter  
Condition  
Min  
21  
Typ  
28  
Max  
35  
Units  
ms  
µs  
Flag Response Delay  
Output Turn-on Delay  
Output Turn-on Rise Time  
Output Turn-off Delay  
Output Turn-off Fall Time  
VIN = VBIAS = 3V, 5V  
RLOAD = 10Ω, CLOAD = 1µF  
RLOAD = 10Ω, CLOAD = 1µF  
RLOAD = 10Ω, CLOAD = 1µF  
RLOAD = 10Ω, CLOAD = 1µF  
600  
1
800  
1.5  
1
1000  
2
tR  
ms  
µs  
tOFF  
tF  
5
24  
µs  
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. OFF is V < 1.0V for MIC2042/MIC2043-1 and V > 4.0V for MIC2042/MIC2043-2. ON is V > 4.0V for MIC2042/MIC2043-1 and V < 1.0V for  
EN  
EN  
EN  
EN  
MIC2042/MIC2043-2.  
6. The current limit is determined as follows: I  
= CLF/R  
.
LIM  
SET  
Timing Diagrams  
tOFF  
50%  
0
0
VEN  
tON  
90%  
10%  
VOUT  
(a) MIC2042/43-1  
50%  
0
0
VEN  
tOFF  
tON  
90%  
10%  
(b) MIC2042/43-2  
VOUT  
Figure 1. Turn-On/Turn-Off Delay  
Increase the load  
0
0
VEN  
VIN 0.2V  
VOUT  
ILIMIT  
0
IOUT  
tFLAG  
0
/FAULT  
Figure 2. Overcurrent Fault Response — MIC2042-2  
January 2005  
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M0512-112603  
MIC2042/2043  
Micrel  
Test Circuit  
M0512-112603  
6
January 2005  
MIC2042/2043  
Micrel  
Typical Characteristics  
Enable Input Threshold  
(Falling)  
vs. Temperature  
Enable Input Threshold  
(Rising)  
Supply Current  
vs. Temperature  
vs. Temperature  
3.5  
3
500  
3.5  
3
450  
VBIAS = 5.5V  
VBIAS = 5.5V  
400  
2.5  
2
2.5  
2
VIN = VBIAS = 5.5V  
350  
VBIAS = 3V  
VBIAS = 3V  
300  
1.5  
1
1.5  
1
VIN = VBIAS = 3V  
250  
VBIAS = 1.6V  
VBIAS = 1.6V  
VIN = VBIAS = 1.6V  
200  
0.5  
0
0.5  
0
150  
100  
-40 -20  
0
20 40 60 80 100  
-40 -20  
0
20 40 60 80 100  
-40 -20  
0
20 40 60 80 100  
TEMPERATURE (°C)  
TEMPERATURE (°C)  
TEMPERATURE (°C)  
Power-Good Reference  
Threshold  
vs. Temperature  
Output Leakage Current  
vs. Temperature  
UVLO Threshold  
vs. Temperature  
600  
500  
400  
300  
200  
100  
0
230  
225  
220  
215  
210  
1.55  
1.5  
VBIAS = 5.5V  
VBIAS = 3V  
1.45  
1.4  
UVLO+  
VTH @ 1.6V to 5.5V  
1.35  
1.3  
UVLO–  
VBIAS = 1.6V  
1.25  
1.2  
-40 -20  
0
20 40 60 80 100  
-40 -20  
0
20 40 60 80 100  
-40 -20  
0
20 40 60 80 100  
TEMPERATURE (°C)  
TEMPERATURE (°C)  
TEMPERATURE (°C)  
On Resistance  
vs. Temperature  
UVLO Adjust PinThreshold  
vs. Temperature  
Flag Response Delay  
vs. Temperature  
80  
70  
60  
50  
40  
30  
20  
10  
0
250  
245  
240  
235  
230  
225  
220  
215  
210  
205  
200  
50  
45  
40  
35  
30  
25  
20  
VIN = VBIAS = 1.6V  
VIN = VBIAS = 3V  
UVLO+  
TFLAG = 5V  
VIN = VBIAS = 5V  
TFLAG = 3V  
20 40 60 80 100  
UVLO–  
20 40 60 80 100  
-40 -20  
0
20 40 60 80 100  
-40 -20  
0
-40 -20  
0
TEMPERATURE (°C)  
TEMPERATURE (°C)  
TEMPERATURE (°C)  
V
Reverse Current Flow  
Turn-On Delay  
vs. Temperature  
BIAS  
Slew Voltage  
vs. Temperature  
vs. Output Voltage  
900  
850  
800  
750  
700  
650  
600  
550  
500  
20  
18  
16  
14  
12  
10  
8
25  
20  
15  
10  
5
VIN = VBIAS = 5.5V  
VIN = V BIAS = 5V  
VIN = VBIAS = 3V  
VIN = V BIAS = 3V  
VIN = VBIAS = 1.6V  
6
VIN = GND  
VBIAS = 1.6V  
4
VIN = V BIAS = 1.6V  
2
0
0
-40 -20  
0
20 40 60 80 100  
-40 -20  
0
20 40 60 80 100  
2
2.5  
3
3.5  
V
4
4.5  
(V)  
5 5.5 6  
TEMPERATURE (°C)  
TEMPERATURE (°C)  
OUT  
January 2005  
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M0512-112603  
MIC2042/2043  
Micrel  
Functional Characteristics  
M0512-112603  
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January 2005  
MIC2042/2043  
Micrel  
January 2005  
9
M0512-112603  
MIC2042/2043  
Micrel  
Functional Diagram  
MIC2042/43 Block Diagram  
M0512-112603  
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January 2005  
MIC2042/2043  
Micrel  
Programmable Current Limit  
Functional Description  
The MIC2042/43 is designed to prevent damage to the  
external load by limiting the maximum amount of current it  
can draw. The current limit is programmed by an external  
TheMIC2042andMIC2043arehigh-sideN-Channelswitches  
equipped with programmable current limit up to 3A for use in  
generalpurposepowerdistributionapplications.Theswitches,  
availablewithactive-highoractive-lowenableinputs,provide  
output slew-rate control and circuit protection via thermal  
shutdown and an optional output latch during overcurrent  
conditions.  
resistor (R  
) connected from ILIM to ground and becomes  
SET  
active when the output voltage is at least 200mV below the  
voltage at the input to the device. The limiting current value  
is defined by the current limit factor (CLF) divided by R  
and the MIC2042/43 will limit from 0.5A to 3A with a set point  
,
SET  
Input and Output  
accuracy of ±22%. In programming the nominal current limit,  
V
suppliespowertotheinternalcircuitryoftheswitchand  
the value of R  
is determined using the following equation:  
BIAS  
SET  
must be present for the switch to operate. V is connected to  
the drain of the output MOSFET and sources power to the  
IN  
390A × Ω  
CLF  
ILIMIT  
(
=
)
RSET  
=
(1)  
switched load. V must be less than or equal to V  
. V  
ILIMIT  
IN  
BIAS OUT  
is the source terminal of the output MOSFET and attaches to  
the load. In a typical circuit, current flows from V to V  
Andgiventhe±22%toleranceofthecurrentlimitfactor(CLF),  
the external resistor is bound by:  
IN  
OUT  
toward the load. If V  
is greater than V , current will flow  
OUT  
IN  
103Ω ≤ R  
≤ 970Ω  
(2)  
from V  
to V since the switch is bi-directional when the  
SET  
OUT  
IN  
deviceisenabled. Whendisabled(OFF), theswitchwillblock  
current flow from either direction.  
The graphs below (Figure 3) display the current limit factor  
characteristic over the full temperature range at the indicated  
voltage. These curves can be used as a point of reference in  
determining the maximum variation in the device’s current  
limit over the full temperature range. For example: With  
Enable Input  
Enable, the ON/OFF control for the output switch, is a digital  
input available as an active-high (–1) or active-low (–2)  
signal. TheENpin, referencedtoapproximately0.5× VBIAS,  
must be driven to a clearly defined logic high or logic low.  
Failure to observe this requirement, or allowing EN to float,  
will cause the MIC2042/43 to exhibit unpredictable behavior.  
EN should not be allowed to go negative with respect to  
ground, nor allowed to exceed VBIAS. Failure to adhere to  
these conditions may result in damage to the device.  
V
(R  
= V  
= 3.0V and a nominal 2A current limit  
IN  
BIAS  
= 192Ω), the low and high current limit settings for the  
SET  
MIC2042/43 would be 1.66A and 2.34A, respectively, as  
shown on the 3V graph using the 192Ω reference point.  
When current limiting occurs, the MIC2042 and MIC2043  
respond differently. Upon first reaching the limiting current  
both devices restrict current flow, allowing the load voltage to  
drop below V . If the VIN-to-VOUT differential voltage ex-  
IN  
Undervoltage Lockout  
ceeds 200mV, then a fault condition is declared and the fault  
delaytimerisstarted.Ifthefaultconditionpersistslongerthan  
the delay period, typically 28ms, then the /FAULT output  
asserts low. At this point, the MIC2042 will continue to supply  
When the switch is enabled, undervoltage lockout (UVLO)  
monitors the input voltage, V , and prevents the output  
IN  
MOSFET from turning on until V exceeds a predetermined  
IN  
level, nominally set at 1.45V. The UVLO threshold is adjust-  
ableandcanbevariedbyapplyinganexternalresistordivider  
to the UVLOIN pin from VIN to GND. The resistive divider  
networkisrequiredwhentheinputvoltageisbelow1.5V. The  
UVLO threshold is internally preset to 1.45V if the UVLOIN  
pin is left open. See “Applications Information” section.  
current to the load at the limiting value (I  
MIC2043 will latch off its output.  
), whereas the  
LIMIT  
Current Limit  
Current Limit  
Current Limit  
vs. R  
vs. R  
vs. R  
SET  
SET  
SET  
4
3.5  
3
4
3.5  
3
4
3.5  
3
–40°C to +85°C  
VIN = VBIAS = 5V  
–40°C to +85°C  
VIN = VBIAS = 3V  
–40°C to +85°C  
VIN = VBIAS = 1.6V  
2.5  
2
2.5  
2
2.5  
2
CLF (HI)  
CLF (HI)  
CLF (HI)  
1.5  
1
1.5  
1
1.5  
1
CLF (LO)  
CLF (LO)  
0.5  
0
0.5  
0
0.5  
0
CLF (LO)  
0
120 240 360 480 600 720 840 960  
(Ω)  
0
120 240 360 480 600 720 840 960  
(Ω)  
0
120 240 360 480 600 720 840 960  
(Ω)  
R
R
R
SET  
SET  
SET  
Figure 3. Current Limit Factor  
January 2005  
11  
M0512-112603  
MIC2042/2043  
Micrel  
/FAULT  
off until either the fault load is removed from VOUT or the EN  
inputiscycledON-OFF-ON. IfthefaultisstillpresentafterEN  
has been cycled, the MIC2043 will again shut off all power to  
the load after 28ms. Once the fault has been removed, then  
normal operation will resume.  
The /FAULT signal is an N-Channel, open-drain MOSFET  
output. An external pull-up resistor tied to a maximum 6V rail  
is required for the /FAULT pin. The /FAULT pin is asserted  
(active-low) when either an overcurrent or thermal shutdown  
conditionoccurs. DuringahotinsertofaPCBorwhenturning  
on into a highly capacitive load, the resulting high transient  
inrush current may exceed the current limit threshold of the  
MIC2042/43. In the case where an overcurrent condition  
occurs, /FAULT will assert only after the flag delay time has  
elapsed, typically 28ms. This ensures that /FAULT is as-  
serted only upon valid overcurrent conditions and that nui-  
sance error reporting is prevented.  
Open Load Detection  
TheMIC2043willautomaticallyresetitsoutputwhenthefault  
load is cleared. This is accomplished by applying a small  
current to VOUT and watching for the voltage at VOUT to rise  
to within 200mV of VIN. This current is supplied by an internal  
resistor connected to VIN and is connected to VOUT when  
MIC2043 latches off.  
Power-Good Detection  
Thermal Shutdown  
TheMIC2042/43candetectwhentheoutputvoltageisabove  
orbelowapresetthresholdthatismonitoredbyacomparator  
at the PGREF input. The PWRGD signal is an N-Channel  
open-drain MOSFET output and an external pull-up resistor  
up to a 6V maximum rail is required for the PWRGD pin.  
Whenever the voltage at the PGREF pin exceeds its thresh-  
For the MIC2042, thermal shutdown is employed to protect  
the device from damage should the die temperature exceed  
safe margins due to a short circuit or an excessive load.  
Thermal shutdown shuts off the output MOSFET and asserts  
the/FAULToutputifthedietemperatureexceeds140°C.The  
MIC2042automaticallyresetsitsoutputandresumessupply-  
ing current to the load when the die temperature drops to  
120°C. If the fault is still present, the MIC2042 will quickly re-  
heat and shut down again. This process of turning  
ON-OFF-ON is called thermal cycling and will continue as  
long as the power switch is enabled while the fault or  
excessive load is present.  
old (V ), typically 230mV, the PWRGD output is asserted.  
TH  
Usingthetypicalapplicationscircuitfrompage1thatswitches  
3.3V as an example, the output voltage threshold determin-  
ing “power is good” is calculated by the following equation:  
R2  
R3  
VOUT(GOOD) = VTH × 1+  
(3)  
Depending on PCB layout (including thermal considerations  
such as heat sinking), package, and ambient temperature, it  
may take several hundred milliseconds from the incidence of  
the fault to the output MOSFET being shut off.  
In substituting the resistor values of the circuit and the typical  
PGREF threshold, the resulting V is calculated as  
3.0V for this 3.3V switching application.  
OUT(GOOD)  
Slew  
Circuit Breaker Function (MIC2043)  
The MIC2042/43’s output rise time is controlled at turn-on to  
a minimum of 1.5ms and is controlled by an internal slew-rate  
limiting circuit. A slew-rate adjustment control pin is available  
for applications requiring slower rise times. By placing a  
capacitor between SLEW and ground, longer rise times can  
beachieved.Forfurtherdetail,seethe“ApplicationsInforma-  
tion” section.  
The MIC2043 is designed to shut off all power to the load  
when a fault condition occurs, just as a circuit breaker would  
do. A fault condition is deemed to be anytime the output  
current exceeds the current limit for more than the flag delay  
period, nominally 28ms. Once the output shuts off, it remains  
M0512-112603  
12  
January 2005  
MIC2042/2043  
Micrel  
linear response. See the “Functional Characteristics” plots.  
Table 1 shows the rise time for various standard capacitor  
values.Additionally,theoutputturn-ontimemustbelessthan  
the nominal flag delay of 28ms in order to avoid nuisance  
tripping of the /FAULT output. This limit is imposed by the  
current limiting circuitry which monitors the (VIN – VOUT)  
differential voltage and concludes a fault condition is present  
if the differential voltage exceeds 200mV for more than the  
flag delay period. For the MIC2043, the /FAULT will assert  
and the output will latch off if the output is not within 200mV  
of the input before the flag delay times out. When using the  
active-low (–2) option with the EN input tied to ground, slew  
control is functional during initial start-up but does not func-  
tion upon resetting the input power to the device. In order for  
the SLEW control to operate during consecutive system  
restarts, the EN pin must reset (toggle OFF to ON).  
Applications Information  
Input and Output  
Supply Bypass Filtering  
The need for input supply bypass is necessary due to several  
factors, most notably the input/output inductance along the  
power path, operating current and current limit, and output  
capacitance. A 0.1µF to 0.47µF bypass capacitor positioned  
very close to the VIN pin to GND of the device is strongly  
recommended to filter high frequency oscillations due to  
inductance. Also, a sufficient bypass capacitor positioned  
close to the input source to the switch is strongly advised in  
order to suppress supply transient spikes and to limit input  
voltage droop. Inrush current increases with larger output  
capacitance, thus the minimum value of this capacitor will  
require experimental determination for the intended applica-  
tion and design. A good starting point is a capacitor between  
4.7µF to 15µF. Without these bypass capacitors, an extreme  
overload condition such as a short circuit, or a large capaci-  
tive load, may cause either the input supply to exceed the  
maximum rating of 6V and possibly cause damage to the  
internal control circuitry or allow the input supply to droop and  
fall out of regulation and/or below the minimum operating  
voltage of the device.  
UVLO Threshold Setting With Low Input Voltages  
When the switching voltage is below 1.6V, the device’s  
standard UVLO threshold (1.45V nominal) will hinder the  
output MOSFET in switching VIN to VOUT. In this case, the  
use of the UVLOIN pin is required to override the standard  
UVLO threshold and set a new, lower threshold for the lower  
input voltage. An external resistive divider network con-  
nected at the UVLOIN pin is used to set the new threshold.  
Due to the ratio of the internal components, the total series  
resistance of the external resistive divider should not exceed  
200kΩ.ThecircuitshowninFigure4illustratesanapplication  
that switches 0.8V while the device is powered from a  
separate 2.5V power supply. The UVLO threshold is set by  
the following equation:  
Output Capacitance  
WhentheMIC2042dieexceedstheovertemperaturethresh-  
old of approximately 140°C, the device can enter into a  
thermal shutdown mode if the die temperature falls below  
120°C and then rises above 140°C in a continuous cycle.  
With the VOUT and /FAULT outputs cycling on and off, the  
MIC2042 will reset the /FAULT while in an overtemperature  
fault condition if the output voltage is allowed to swing below  
ground. The inductance present at the output must be neu-  
tralizedbycapacitanceinordertoensurethattheoutputdoes  
not fall below ground. In order to counter the board parasitic  
inductance and the inductance of relatively short-length  
power cable (≤ 1ft., 16 to 20 gauge wire), a minimum output  
capacitanceof22µFisstronglyrecommendedandshouldbe  
placed close to the VOUT pin of the MIC2042. For applica-  
tions that use more than a foot of cable, an additional  
10µF/ft. is recommended.  
R2  
R3  
V
= 0.23V × 1+  
(4)  
UVTH  
In substituting the resistor values from Figure 4, the resulting  
UVLO threshold (V ) is calculated as 0.6V for this 0.8V  
UVTH  
switching application. When using the UVLOIN pin to set a  
new UVLO threshold, an optional 0.1µF to 1.0µF capacitor  
from UVLOIN to GND may be used as a glitch filter in order  
to avoid nuisance tripping of the UVLO threshold. If the  
UVLOIN pin is not in use, this pin should be left open  
(floating). The use of a pull-down resistor to ground will offset  
the ratio of the internal resistive divider to this pin resulting in  
a shift in the UVLO threshold. To bypass (disable) UVLO,  
connect the UVLOIN pin directly to the VIN pin of the  
MIC2042/43.  
Reverse Current Block  
The MIC2042/43 provides reverse current flow block through  
theoutputMOSFETifthevoltageatVOUTisgreaterthanVIN  
when the device is disabled. The VBIAS supply pin has a  
limited reverse current flow if the voltage at VOUT is pulled  
above VBIAS when the device is disabled. A graph of the  
V
= V  
= 5V/3V; C  
= 47µF; I = 1A  
LOAD  
Conditions:  
IN  
BIAS  
LOAD  
V
reverse current flow is shown in the “Functional Char-  
BIAS  
acteristics” plots. The reverse current for V  
can be  
C
(µF)  
Rise Time (ms)  
BIAS  
SLEW  
completely blocked by inserting a Schottky diode from the  
VBIAS pin (cathode) to the supply (anode). However, the  
minimum voltage of 1.6V must be supplied to VBIAS after  
accounting for the voltage drop across the diode.  
5V  
3
3V  
4.75  
15  
0.01  
0.033  
0.047  
0.1  
10.5  
14  
21  
Output Slew-Rate Adjustment  
32  
46  
Theoutputslew-ratefortheMIC2042/43canbesloweddown  
by the capacitor (16V rating, minimum; 25V suggested)  
between SLEW and GND. The slew-rate control circuitry is  
independent of the load capacitance and exhibits a non-  
Table 1. Typical Output Rise Time for Various C  
SLEW  
January 2005  
13  
M0512-112603  
MIC2042/2043  
Micrel  
Figure 4. Lower UVLO Setting  
Power Dissipation  
heatupconsiderably. Thefollowinglistcontainssomeuseful  
suggestions for PCB layout design of the MIC2042/43 in  
order to prevent the die from overheating under normal  
operating conditions:  
Power dissipation depends on several factors such as the  
load, PCB layout, ambient temperature, and package type.  
The following equations can be used to calculate power  
dissipation and die temperature.  
1. Supply additional copper area under the device  
to remove heat away from the IC.  
Calculation of power dissipation can be accomplished by the  
following equation:  
2
See “Application Hint 17” for a general guideline  
in calculating the suggested area.  
P = R  
× (I )  
OUT  
(5)  
D
DS(ON)  
To relate this to junction temperature, the following equation  
can be used:  
2. Provide additional pad area on the corner pins of  
the MIC2042/43 IC for heat distribution.  
T = P × Rθ + T  
(6)  
where T = junction temperature, T = ambient temperature  
J
D
JA  
A
3. Tie the common power pins (VIN = pins 8 and  
12 and VOUT = pins 10, 11, 14 for the 14-pin  
TSSOP, VIN = pins 5 and 7 and VOUT = pins 6  
and 8 for the 8-pin SOP) together in a manner  
such that the traces entering and leaving the  
device have a uniform width sufficient for the  
application’s current requirements plus added  
margin (25% minimum recommended).  
J
A
and Rθ is the thermal resistance of the package.  
JA  
Printed Circuit Board Hot-Plug  
The MIC2042/43 are ideal inrush current limiting power  
switches suitable for hot-plug applications. Due to the inte-  
grated charge pump, the MIC2042/43 present a high imped-  
ance when in the off state and the device slowly becomes a  
low impedance as it turns on. This effectively isolates power  
supplies from highly capacitive loads by reducing inrush  
currentduringhot-plugevents.Thissamefeaturealsocanbe  
used for soft-start requirements.  
Ex: For 2A maximum current, design traces for  
2.5A capability.  
4. For PCB trace width calculation, there are  
numerous calculator programs available on the  
internet and elsewhere. As a general rule of  
thumb, 15-20 mils for every 1A of current when  
using 1oz. copper. However, the trace width  
calculators often take into account maximum  
temperature increase constraints, as well as  
layer arrangement, in determining the PCB trace  
widths.  
PCB Layout Recommendations  
The MIC2042 and MIC2043 have very low on-resistance,  
typically 40mΩ, and the switches can provide up to 3A of  
continuous output current. Under such heavy loads, the  
power consumed by the devices may cause the devices to  
M0512-112603  
14  
January 2005  
MIC2042/2043  
Micrel  
Package Information  
0.026 (0.65)  
MAX)  
PIN 1  
0.157 (3.99)  
0.150 (3.81)  
DIMENSIONS:  
INCHES (MM)  
0.020 (0.51)  
0.013 (0.33)  
0.050 (1.27)  
TYP  
45°  
0.0098 (0.249)  
0.0040 (0.102)  
0.010 (0.25)  
0.007 (0.18)  
0°–8°  
0.197 (5.0)  
0.189 (4.8)  
0.050 (1.27)  
0.016 (0.40)  
SEATING  
PLANE  
0.064 (1.63)  
0.045 (1.14)  
0.244 (6.20)  
0.228 (5.79)  
8-Pin SOP (M)  
4.50 (0.177)  
4.30 (0.169)  
DIMENSIONS:  
MM (INCH)  
6.4 BSC (0.252)  
0.30 (0.012)  
0.19 (0.007)  
5.10 (0.200)  
4.90 (0.193)  
0.20 (0.008)  
0.09 (0.003)  
1.10 MAX (0.043)  
0.65 BSC  
(0.026)  
1.00 (0.039) REF  
8°  
0°  
0.15 (0.006)  
0.05 (0.002)  
0.70 (0.028)  
0.50 (0.020)  
14-Pin TSSOP (TS)  
MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA  
TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 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 at Purchaser’s own risk and Purchaser agrees to fully indemnify  
Micrel for any damages resulting from such use or sale.  
© 2005 Micrel, Incorporated.  
January 2005  
15  
M0512-112603  

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