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19-4363; Rev 2; 2/10
50mA to 600mA Programmable Current-Limit Switches
General Description
The MAX4995A/MAX4995AF/MAX4995AL/MAX4995B/ MAX4995C programmable current-limit switches feature internal current limiting to prevent damage to host devices due to faulty load conditions. These analog switches feature a low 130m (typ) on-resistance and operate from a +1.7V to +5.5V input voltage range. The current limit is adjustable from 50mA to 600mA, making these devices ideal for SDIO (secure digital input/output) and other load-switching applications. Each device in the family handles an overcurrent event differently depending on the option selected. The MAX4995A/MAX4995AF/MAX4995AL go into an autoretry mode, the MAX4995B latches off the switch, and the MAX4995C places the device in a continuous current-limit mode. Additional safety features include thermal shutdown to prevent overheating and reversecurrent blocking to prevent current from being driven back into the source. The MAX4995A/MAX4995AF/MAX4995AL/MAX4995B/ MAX4995C are available in a tiny 10-pin, 1.4mm x 1.8mm UTQFN, a 6-pin SOT23, or an 8-pin, 2mm x 2mm TDFN package and operate over the -40C to +125C extended temperature range. 10% Accurate Current Limit Overload FLAG Threshold Low Dropout Voltage Short-Circuit Protection Thermal Shutdown Reverse-Current Protection 170A (typ) Supply Current +1.7V to +5.5V Supply Voltage Range Tiny 10-Pin, 1.4mm x 1.8mm UTQFN Package
Features
50mA to 600mA Programmable Current Limit
MAX4995A/AF/AL/MAX4995B/MAX4995C
Applications
SDIO Ports USB Ports Notebook VGA Ports GPS Cell Phones MP3 Players UTCA/ATCA Platforms
Ordering Information/Selector Guide
PART MAX4995AAUT+T* MAX4995AAVB+T MAX4995AATA+T MAX4995AFAUT+T* MAX4995AFAVB+T MAX4995AFATA+T* MAX4995ALAUT+T* MAX4995ALAVB+T MAX4995ALATA+T* MAX4995BAUT+T* MAX4995BAVB+T MAX4995BATA+T* MAX4995CAUT+T* MAX4995CAVB+T MAX4995CATA+T* PIN-PACKAGE 6 SOT23 10 UTQFN 8 TDFN-EP** 6 SOT23 10 UTQFN 8 TDFN-EP** 6 SOT23 10 UTQFN 8 TDFN-EP** 6 SOT23 10 UTQFN 8 TDFN-EP** 6 SOT23 10 UTQFN 8 TDFN-EP** ON POLARITY Active-High Active-High Active-High Active-High Active-High Active-High Active-Low Active-Low Active-Low Active-High Active-High Active-High Active-High Active-High Active-High OVERCURRENT RESPONSE Autoretry Autoretry Autoretry Autoretry Autoretry Autoretry Autoretry Autoretry Autoretry Latchoff Latchoff Latchoff Continuous Continuous Continuous SHORT-CIRCUIT RESPONSE Normal Normal Normal Fast Fast Fast Normal Normal Normal Normal Normal Normal Normal Normal Normal TOP MARK +ACNZ +AAM +ABL +ACOE +AAR +ACO +ACDA +AAN +ABM +ACDB +AAO +ABN +ACOD +AAQ +ABP
All devices operate over the -40C to +125C temperature range. +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. *Future product. Contact factory for availability. **EP = Exposed pad.
Typical Operating Circuit appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
50mA to 600mA Programmable Current-Limit Switches MAX4995A/AF/AL/MAX4995B/MAX4995C
ABSOLUTE MAXIMUM RATINGS
IN, ON, ON, FLAG, OUT, and SETI to GND .............-0.3V to +6V Current into Any Pin (Except IN, OUT)................................20mA OUT Short Circuit to GND .................................................800mA Continuous Power Dissipation (TA = +70C) (Note 1) 10-Pin UTQFN (derate 6.99mW/ C above TA = +70C) ..559mW 6-Pin SOT23 (derate 13.4mW/ C above TA = +70C)...1072.4mW 8-Pin TDFN (derate 11.9mW/ C above TA = +70C) ....953.5mW Junction-to-Ambient Thermal Resistance (JA) (Note 2).....................................................................143.1C/W Operating Temperature Range .........................-40C to +125C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+150C Lead Temperature (soldering, 10s) .................................+300C
Note 1: These power limits are defined by the thermal characteristics of the package, maximum function temperature (+150C), and the JEDEC51-7 defined setup. Maximum power dissipation could be lower, limited by the thermal-shutdown protection included in this IC. Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VIN = +1.7V to +5.5V, RSETI = 94.3k, CIN = 1F, and TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at VIN = +3.3V, TA = +25C.)
PARAMETER SUPPLY OPERATION Operating Voltage Quiescent Current Latchoff Current Shutdown Forward Current Shutdown Reverse Current INTERNAL FET Switch-On Resistance Normalized Current-Limit Accuracy (RSETI + 2.48) x ILIM Product Reverse Blocking Current Reverse Blocking Threshold FLAG Assertion Drop Voltage Threshold ON, ON INPUT ON, ON Input Leakage ON, ON Input Logic-High Voltage ON, ON Input Logic-Low Voltage ILEAK VIH VIL VON, V ON = VIN or GND -1 1.6 0.4 +1 A V V VFA RON VIN = 3.3V, IOUT lower than ILIM ILIM = 50mA to 600mA, VIN - VOUT = 1V, VIN = 3.3V (Note 3) ILIM = 50mA to 600mA, VIN - VOUT = 1V, VIN = 3.3V VOUT > VIN + 300mV after reverse-currentlimit shutdown VOUT = VIN + 300mV, OUT falling until switch turns on Increase (VIN - VOUT) drop until FLAG asserts, I OUT limiting, VIN = 3.3V 35 110 650 0.9 26138 130 1 29042 350 1.1 31946 10 210 m -- V A mV mV VIN IQ ILATCH ISHDN IRSHDN IOUT = 0, switch on, VIN = 3.3V VIN = 3.3V, IOUT = 0 after an overcurrent fault (MAX4995B) VON = 0, V ON = VIN, VIN = 5.5V, VOUT = 0 VON = 0, V ON = VIN, VIN = 1.7V, VOUT = 5.5V (current into OUT) 1.7 170 8 0.01 0.01 5.5 300 15 5 1 V A A A A SYMBOL CONDITIONS MIN TYP MAX UNITS
2
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50mA to 600mA Programmable Current-Limit Switches
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +1.7V to +5.5V, RSETI = 94.3k, CIN = 1F, and TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at VIN = +3.3V, TA = +25C.)
PARAMETER FLAG OUTPUT FLAG Output Logic-Low Voltage FLAG Output Leakage Current DYNAMIC Turn-On Time Turn-Off Time tSS tOFF VIN = 3.3V, COUT = 1F, RL = 20 , Figure 1, (Note 4) Switch from on to off, VIN = 3.3V, COUT = 1F, RL = 20 , Figure 1 (Note 4) VIN = 3.3V, RSETI = 578k , output high and then short-circuit applied (Note 5) MAX4995A/MAX4995AF/MAX4995AL (Note 5) MAX4995A/AL/B/C MAX4995AF 10 320 +150 15 120 120 5 s 1.5 16.3 22.6 723.2 ms ms C C s s ISINK = 1mA VIN = VFLAG = 5.5V, FLAG deasserted 0.4 1 V A SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX4995A/AF/AL/MAX4995B/MAX4995C
Current-Limit Reaction Time
tLIM
Blanking Time Retry Time THERMAL PROTECTION Thermal Shutdown Thermal-Shutdown Hysteresis
tBLANK tRETRY
Note 3: ILIM is forward current limit.
ILIM (mA) =
29042(V) RSETI (k) + 2.48 (k)
Note 4: Turn-on time and turn-off time are defined as the difference in the time between when the output crosses 10% and 90% of the final output voltage. Note 5: Blanking time and retry time are generated by the same oscillator. Therefore, the ratio of
t RETRY t BLANK
is a constant value of 32. See Figures 2 and 3.
tSS 90% VOUT 10% tOFF 10% 90%
Figure 1. Timing Diagram for Measuring Turn-On Time (tSS) and Turn-Off Time (tOFF).
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50mA to 600mA Programmable Current-Limit Switches MAX4995A/AF/AL/MAX4995B/MAX4995C
Typical Operating Characteristics
(VIN = +3.3V, CIN = 1F, COUT = 1F, RSETI = 94.2k, TA = +25C, unless otherwise noted.)
CURRENT LIMIT vs. SUPPLY VOLTAGE
MAX4995A toc01
NORMALIZED CURRENT LIMIT vs. TEMPERATURE
MAX4995AL 1.075 NORMALIZED CURRENT LIMIT 1.050 1.025 1.000 0.975 0.950 0.925
MAX4995A toc02
315 MAX4995AL 310 CURRENT LIMIT (mA) 305 300 295 290 285 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
1.100
0.900 5.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) SUPPLY VOLTAGE (V)
CURRENT-LIMIT RESPONSE (MAX4995A)
MAX4995A toc03
CURRENT-LIMIT RESPONSE (MAX4995AF)
MAX4995A toc04
SUDDEN SHORT APPLIED AT OUTPUT
SUDDEN SHORT APPLIED AT OUTPUT
VOUT (2V/div)
VOUT (2V/div)
IOUT (10A/div)
IOUT (10A/div)
10s/div
10s/div
CURRENT-LIMIT RESPONSE
MAX4995A toc05
QUIESCENT SUPPLY CURRENT vs. SUPPLY VOLTAGE
280 260 240 220 200 180 160 140 120 MAX4995A
MAX4995A toc06
300 QUIESCENT SUPPLY CURRENT (A)
RLOAD = 8 VOUT (2V/div)
IOUT (100mA/div)
4ms/div
100 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
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50mA to 600mA Programmable Current-Limit Switches MAX4995A/AF/AL/MAX4995B/MAX4995C
Typical Operating Characteristics (continued)
(VIN = +3.3V, CIN = 1F, COUT = 1F, RSETI = 94.2k, TA = +25C, unless otherwise noted.)
QUIESCENT SUPPLY LIMIT vs. TEMPERATURE
MAX4995A toc07
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX4995A toc08
SHUTDOWN FORWARD CURRENT vs. TEMPERATURE
MAX4995C SHUTDOWN FORWARD CURRENT (nA) 70 60 50 40 30 20 10 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) VIN = 1.7V VIN = 5V
MAX4995A toc09
260 250 QUIESCENT SUPPLY CURRENT (A) 240 230 220 210 200 190 180 170 160 150 140
2.50 SHUTDOWN SUPPLY CURRENT (A) 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 VIN = 3.3V VIN = 5V MAX4995AL
80
VIN = 5V
VIN = 3.3V
MAX4995AL -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
SHUTDOWN REVERSE CURRENT vs. TEMPERATURE
MAX4995A toc10
LATCHOFF CURRENT vs. TEMPERATURE
MAX4995A toc11
NORMALIZED ON-RESISTANCE vs. SUPPLY VOLTAGE
1.035 1.030 1.025 1.020 1.015 1.010 1.005 1.000 0.995 0.990 0.985 0.980 MAX4995C IOUT < ILIM
MAX4995A toc12
225 SHUTDOWN REVERSE CURRENT (nA) 200 175 150 125 100 75 50 25 0 VIN = 1.7V VIN = 5V MAX4995C VOUT = 5.5V
20 MAX4995B 18 LATCHOFF CURRENT (A) 16 14 12 10 8 6 VIN = 3.3V VIN = 5V
1.040
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
NORMALIZED ON-RESISTANCE
1.7
2.2
2.7
3.2
3.7
4.2
4.7
5.2
SUPPLY VOLTAGE (V)
NORMALIZED ON-RESISTANCE vs. TEMPERATURE
MAX4995A toc13
SWITCH TURN-ON TIME vs. TEMPERATURE
MAX4995A toc14
SWITCH TURN-OFF TIME vs. TEMPERATURE
1.5 SWITCH TURN-OFF TIME (ms) 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 VIN = 3.3V VIN = 5V MAX4995C ILOAD = 10mA
MAX4995A toc15
1.5 1.4 NORMALIZED ON-RESISTANCE 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 MAX4995C VIN = 3.3V
180 170 SWITCH TURN-ON TIME (s) 160 150 140 130 120 110 100 VIN = 3.3V VIN = 5V MAX4995C ILOAD = 10mA
1.6
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
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50mA to 600mA Programmable Current-Limit Switches MAX4995A/AF/AL/MAX4995B/MAX4995C
Typical Operating Characteristics (continued)
(VIN = +3.3V, CIN = 1F, COUT = 1F, RSETI = 94.2k, TA = +25C, unless otherwise noted.)
SWITCH TURN-ON TIME RESPONSE
MAX4995A toc16
SWITCH TURN-OFF TIME RESPONSE
MAX4995A toc17
VON (5V/div) VON (5V/div) VOUT (2V/div) VOUT (2V/div) 200s/div 200s/div
FLAG RESPONSE (OVERLOAD) CONDITION
MAX4995A toc18
SWITCH DROPOUT VOLTAGE vs. TEMPERATURE
18 SWITCH DROPOUT VOLTAGE (mV) IOUT (200mA/div) VOUT (2V/div) 17 16 15 14 13 12 11 10 VIN = 3.3V -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) MAX4995A ILOAD = 100mA
MAX4995A toc19
19
VFLAG (2V/div)
100ms/div
9
IOUT/FLAG vs. VDROP (VIN - VOUT)
MAX4995B 300 250 IOUT (mA) 200 150 100 50 VIN = 5.5V 0 0 VDROP (mV) 0 1
MAX4995A toc20
350
70 140 210 280 350 420 490 560 630 700
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FLAG (LOGIC-LEVEL STATUS)
50mA to 600mA Programmable Current-Limit Switches
Pin Configurations
TOP VIEWS
IN 10 N.C. 9 OUT 8 OUT IN 1 MAX4995A/MAX4995AF MAX4995AL/MAX4995B MAX4995C 7 OUT GND 6 N.C. SETI 3 4 5 SETI 3 2 MAX4995A/MAX4995AF MAX4995AL/MAX4995B MAX4995C 5 IN MAX4995A/MAX4995AF MAX4995AL/MAX4995B MAX4995C *EP 1 IN 2 IN 3 4 1 6 FLAG OUT 8 N.C. 7 SETI 6 GND 5
MAX4995A/AF/AL/MAX4995B/MAX4995C
FLAG
2
4
ON (ON)* +
ON (ON)* GND
UTQFN (1.4mm x 1.8mm)
*( ) FOR THE MAX4995AL ONLY. **EXPOSED PAD. CONNECT EP TO GND.
SOT23 (1.6mm x 2.9mm)
FLAG ON (ON)*
TDFN (2mm x 2mm)
Pin Description
PIN (UTQFN) MAX4995AL MAX4995_ PIN (TDFN-EP) MAX4995AL PIN (SOT23) MAX4995_ MAX4995_ MAX4995AL NAME FUNCTION Power Input. Bypass IN with a 1F ceramic capacitor to ground. Use higher capacitance to prevent large load transients from pulling down the supply voltage if necessary. Connect both power inputs (IN) together. Open-Drain, Overload Indicator Output. FLAG goes low when the overload fault duration exceeds the blanking time, reverse current is detected, thermal shutdown mode is active, or SETI is connected to ground. Active-Low, Switch-On Input. Drive ON low to turn on the switch. Active-High, Switch-On Input. Drive ON high to turn on the switch. Ground Overload Current Limit Adjust. Connect a resistor from SETI to ground to program the overcurrent limit. Do not connect any capacitance larger than 20pF to SETI.
1, 10
1, 10
1, 2
1, 2
5
5
IN
2
2
3
3
6
6
FLAG
3 -- 4
-- 3 4
4 -- 5
-- 4 5
4 -- 2
-- 4 2
ON ON GND
5
5
6
6
3
3
SETI
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50mA to 600mA Programmable Current-Limit Switches MAX4995A/AF/AL/MAX4995B/MAX4995C
Pin Description (continued)
PIN (UTQFN) MAX4995AL 6, 9 MAX4995_ 6, 9 PIN (TDFN-EP) MAX4995AL 7 PIN (SOT23) MAX4995_ -- MAX4995_ MAX4995AL 7 -- NAME N.C. FUNCTION No Connect. Not internally connected. Switch Output. Bypass OUT with a 1F capacitor to ground. Connect both outputs (OUT) together. Exposed Pad. Connect EP to GND. For TDFN package only.
7, 8
7, 8
8
8
1
1
OUT
--
--
--
--
--
--
EP
Functional Diagram
MAX4995A/MAX4995AF/ MAX4995AL/MAX4995B/ MAX4995C
REVERSECURRENT PROTECTION OUT THERMAL SHUTDOWN
IN
UVLO
BUFFER
CONTROL LOGIC
FLAG
TIMING CIRCUITRY
N.C. SOFT-START ON (ON)*
BANDGAP REFERENCE
CURRENT LIMIT BUFFER SETI
GND *( ) FOR THE MAX4995AL ONLY.
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50mA to 600mA Programmable Current-Limit Switches
Detailed Description
The MAX4995A/MAX4995AF/MAX4995AL/MAX4995B/ MAX4995C programmable current-limit switches operate from +1.7V to +5.5V and provide internal current limiting adjustable from 50mA to 600mA. These devices feature a fixed blanking time and a FLAG output that notifies the processor when a fault condition is present.
MAX4995A/AF/AL/MAX4995B/MAX4995C
Table 1. Switch Truth Table
MAX4995_/ MAX4995AF ON 0 1 MAX4995AL ON 1 0 SWITCH STATUS Off On
Programmable Current Limit
A resistor from SETI to GND programs the current limit for the switch (see the Setting the Current Limit section). If the output current exceeds the current limit for a time equal to or longer than tBLANK, the output flag asserts and the MAX4995A/MAX4995AF/MAX4995AL enter the autoretry mode. The MAX4995B latches off the switch, and the MAX4995C enters the continuous current-limit mode.
Latchoff (MAX4995B)
When the forward current reaches the current-limit threshold, the tBLANK timer begins counting (Figure 3). FLAG asserts if an overcurrent-limit condition is present for greater than tBLANK time. The timer resets if the overcurrent condition disappears before t BLANK has elapsed. The switch turns off if the overcurrent condition continues beyond the blanking time. Reset the switch by either toggling the control logic (ON) or cycling the input voltage. If the thermal power rating of the package is exceeded during tBLANK, the MAX4995B goes into thermal shutdown.
Autoretry (MAX4995A/MAX4995AF/ MAX4995AL)
When the forward current reaches the current-limit threshold, the tBLANK timer begins counting (Figure 2). FLAG asserts if the overcurrent-limit condition is present for tBLANK. The timer resets if the overcurrent condition disappears before the blanking time (tBLANK) has elapsed. A retry time delay (tRETRY) starts immediately after the blanking time has elapsed and during that time, the switch latches off. At the end of tRETRY, the switch turns on again. If the fault still exists, the cycle repeats. If the fault has been removed, the switch stays on. During this cycle, FLAG stays low. In autoretry if the thermal power rating of the package is exceeded, the MAX4995A/MAX4995AF/MAX4995AL go into thermal shutdown. The autoretry feature saves system power in case of an overcurrent or short-circuit condition. During tBLANK time when the switch is on, the supply current is held at the current limit. During time tRETRY when the switch is off, the current through the switch is zero. Thus, the average output current is much less than the programmed current limit. Calculate the average output current using the following equation: ILOAD = ILIM [tBLANK/(tBLANK + tRETRY)] With a typical tBLANK = 16.3ms and typical tRETRY = 524ms, the duty cycle is 3%, resulting in a 97% power savings over the switch being on the entire time.
Continuous Current Limit (MAX4995C)
When the forward current reaches the forward currentlimit threshold, the MAX4995C limits the output current to the programmed current limit. FLAG asserts if the current limit is present for tBLANK and deasserts when the overload condition is removed. In this mode, if the thermal power rating of the package is exceeded, the MAX4995C goes into thermal shutdown.
Switch-On/Off Control
The ON input for the MAX4995_/MAX4995AF and ON input for the MAX4995AL control the switch; see Table 1. Toggle ON for the MAX4995B to reset the fault condition once the short current is detected and the device shuts down.
Reverse-Current Protection
The MAX4995 features a reverse-current protection circuit that limits the backflow current to 10A when the output voltage exceeds the input voltage by 110mV (typ). The switch turns off and FLAG asserts without waiting for tBLANK to elapse. The switch turns back on and FLAG deasserts when the output voltage drops below the detecting threshold by 10mV (typ).
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9
50mA to 600mA Programmable Current-Limit Switches MAX4995A/AF/AL/MAX4995B/MAX4995C
tBLANK tRETRY tBLANK tRETRY tBLANK tBLANK
OUT
CURRENT LIMIT LOAD CURRENT THE DEVICE GOES TO THERMAL-SHUTDOWN MODE
FLAG
Figure 2. Autoretry Fault Diagram
tBLANK
tBLANK
OUT
CURRENT LIMIT LOAD CURRENT THE DEVICE GOES TO THERMAL-SHUTDOWN MODE
FLAG
Figure 3. Latchoff Fault Diagram
FLAG Indicator
FLAG is an open-drain fault indicator output and requires an external pullup resistor to a DC supply. FLAG goes low when any of the following conditions occurs: * * * *
10
Thermal Shutdown
Thermal-shutdown circuitry protects the devices from overheating. The switch turns off and FLAG goes low immediately when the junction temperature exceeds +150C (typ). The switch turns on again after the device temperature drops by approximately 15C (typ).
The device is in current-limit mode. The OUT voltage is above the IN voltage by more than 110mV (typ). The die temperature exceeds the thermal-shutdown temperature limit of +150C. SETI is connected to ground.
______________________________________________________________________________________
50mA to 600mA Programmable Current-Limit Switches
Applications Information
Setting the Current Limit
A resistor from SETI to ground programs the current-limit value for the MAX4995. Table 2 lists various current limits set by different resistor values at SETI. Shorting SETI to ground asserts FLAG. Use the following formula to calculate the current limit: RSETI (k) = 29042(V) - 2.48 (k) ILIM (mA)
Output Capacitor
For stable operation over the full temperature range and over the full programmable current-limit range, use a 1F ceramic capacitor from OUT to ground. If the load capacitance is too large, then current may not have enough time to charge the capacitance and the device assumes that there is a faulty load condition. Calculate the maximum capacitive load (CMAX) value that can be connected to OUT using the following formula: C MAX ( F) = I LIM (mA) x t BLANK(MIN) (ms ) VIN (V)
MAX4995A/AF/AL/MAX4995B/MAX4995C
Using an RSETI with a value smaller than 45.8k results in a higher current limit. A programmed output current greater than 660mA can damage the device. Connecting any capacitance larger than 20pF to SETI can cause instability.
Table 2. Current Limit vs. Resistor Values
RSETI (k) 45.8 55.6 70.6 94.2 143 191 287 576 (Open) TYPICAL CURRENT LIMIT (mA) 602 500 397 300 200 150 100 50 0
For example, for VIN = 3.3V, tBLANK(MIN) = 10ms, and ILIM = 300mA, CMAX equals 909F. Due to the very fast current-limit reaction time of the MAX4995AF, a larger output capacitance might need to be connected at the output to dampen oscillation due to long wires. Choose a value large enough to ensure OUT doesn't exceed the absolute maximum ratings.
Layout and Thermal Dissipation
To optimize the switch response time to output shortcircuit conditions, it is very important to keep all traces as short as possible to reduce the effect of undesirable parasitic inductance. Place input and output capacitors as close as possible to the device. IN and OUT must be connected with wide, short traces to the power bus. During normal operation, the power dissipation is small and the package temperature change is minimal. If the output is continuously shorted to ground at the maximum supply voltage, the operation of the switches with the autoretry option does not cause problems because the total power dissipated during the short is scaled by the duty cycle: P MAX = VIN(MAX) x I OUT(MAX) x t BLANK t RETRY + t BLANK
Input Capacitor
Connect a capacitor from IN to GND to limit the input voltage drop during momentary output short-circuit conditions. Use a 1F minimum ceramic capacitor for proper device operation. Larger capacitor values reduce the voltage undershoot at the input. Due to the very fast current-limit reaction time of the MAX4995AF, a larger input capacitance might need to be connected at the input to dampen oscillation due to long wires. Choose a value large enough to ensure IN doesn't exceed the absolute maximum ratings.
Attention must be given to the MAX4995C continuous current-limit version when the power dissipation during a fault condition may cause the device to reach thermal shutdown threshold.
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11
50mA to 600mA Programmable Current-Limit Switches MAX4995A/AF/AL/MAX4995B/MAX4995C
Typical Operating Circuit
VCC
1F VIO
IN FLAG ON (ON*) OUT 1F P
SETI RSETI
MAX4995A/ MAX4995AF/ MAX4995AL/ MAX4995B/ MAX4995C
GND
LOAD
N.C.
*( ) FOR THE MAX4995AL ONLY.
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE 10 UTQFN 6 SOT23 8 TDFN PACKAGE CODE V101A1CN+1 U6SN+1 T822+1 DOCUMENT NO. 21-0028 21-0058 21-0168
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50mA to 600mA Programmable Current-Limit Switches
Revision History
REVISION NUMBER 0 1 2 REVISION DATE 11/08 6/09 2/10 Initial release. Corrected the Ordering Information/Selector Guide. * Added TDFN package information to the Ordering Information/Selector Guide, Absolute Maximum Ratings, Pin Description, and Package Information sections. * Added the TDFN pin configuration drawing to the Pin Configurations section. DESCRIPTION PAGES CHANGED -- 1, 11 1, 2, 7, 12
MAX4995A/AF/AL/MAX4995B/MAX4995C
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13
(c) 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

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