Maxim MAX4796EUK-T 450ma/500ma current-limit switch Datasheet

19-2944; Rev 0; 8/03
450mA/500mA Current-Limit Switches
The MAX4796 and MAX4798 have an autoretry feature
where the switch turns off and issues a FLAG to the
microprocessor after the blanking time and then continuously checks to see if the overload condition is present. The switch remains on after the overload condition
disappears and FLAG deasserts.
The MAX4795–MAX4798 are available in tiny, spacesaving, 5-pin SOT23 and 6-pin TDFN (3mm x 3mm)
packages.
Applications
SDIO
PDAs and Palmtop Devices
Cell Phones
Features
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
Guaranteed Current Limit: 450mA and 500mA
Thermal-Shutdown Protection
Reverse-Current Protection
0.2Ω On-Resistance
14ms Guaranteed Blanking Time
FLAG Function
Autoretry (MAX4796/MAX4798)
80µA Supply Current
6µA Latchoff Current
(MAX4795/MAX4797)
0.01µA Shutdown Current
+2V to +4.5V Supply Range
Fast Current-Limit Response Time
Tiny SOT23 and TDFN Packages
UL Certification Pending
Ordering Information
PART
TEMP RANGE
PINPACKAGE
TOP
MARK
AEDI
MAX4795EUK-T
-40°C to +85°C
5 SOT23-5
MAX4795ETT*
40°C to +85°C
6 TDFN-EP**
MAX4796EUK-T
-40°C to +85°C
5 SOT23-5
MAX4796ETT*
-40°C to +85°C
6 TDFN-EP**
MAX4797EUK-T
-40°C to +85°C
5 SOT23-5
MAX4797ETT*
-40°C to +85°C
6 TDFN-EP**
GPS Systems
MAX4798EUK-T
-40°C to +85°C
5 SOT23-5
Hand-Held Devices
MAX4798ETT*
-40°C to +85°C
6 TDFN-EP**
Typical Operating Circuit
—
AEDJ
—
AEDK
—
AEDL
—
*Future product—contact factory for availability.
**EP = Exposed pad.
Selector Guide appears at end of data sheet.
+2.0V TO +4.5V
Pin Configurations
TOP VIEW
IN
ON
MAX4795
MAX4796
MAX4797
MAX4798
µP
FLAG
IN 1
GND 2
TO SDIO PORT
OUT
ON 3
5 OUT
MAX4795
MAX4796
MAX4797
MAX4798
IN 1
OUT 2
4 FLAG N.C. 3
6 ON
MAX4795
MAX4796
MAX4797
MAX4798
5 GND
4 FLAG
GND
SOT23
TDFN
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX4795–MAX4798
General Description
The MAX4795–MAX4798 family of switches feature internal current limiting to prevent damage to host devices
due to faulty load conditions. These analog switches
have a low 0.2Ω on-resistance and operate from a 2.0V
to 4.5V input voltage range. They are available with guaranteed 450mA and 500mA current limits, making them
ideal for SDIO and other load-switching applications.
When the switch is on and a load is connected to the
port, a guaranteed blanking time of 14ms ensures the
transient voltages settle down. If after this blanking time,
the load current is greater than the current limit, the
MAX4795 and MAX4797 switches are turned off and
FLAG is issued to the microprocessor. The switch can be
turned on again by cycling the power or the ON input.
MAX4795–MAX4798
450mA/500mA Current-Limit Switches
ABSOLUTE MAXIMUM RATINGS
IN, ON, FLAG, OUT to GND .....................................-0.3V to +6V
OUT Short Circuit to GND .................................Internally Limited
Continuous Power Dissipation (TA = +70°C)
5-Pin SOT23 (derate 7.1mW/°C above +70°C)............571mW
6-Pin TDFN (derate 24.4mW/°C above +70°C) .........1951mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
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 = +2.0V to +4.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VIN = 3.3V, TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
Operating Voltage
VIN
Quiescent Current
IQ
CONDITIONS
125
µA
VIN = +3.3V
6
10
µA
1
µA
ISHDN
VON = 0V
0.03
MAX4795/MAX4796, VIN = 3.3V, VOUT = GND
450
720
MAX4797/MAX4798, VIN = 3.3V, VOUT = GND
500
800
MAX4795/MAX4796
720
MAX4797/MAX4798
800
ON Input Leakage
-1
Shutdown Forward Leakage
VON = 0V, VOUT = 0V
Shutdown Reverse Leakage
VON = 0V, VIN = 2V, VOUT = 4.5V
ON Input Logic High Voltage
VIH
ON Input Logic Low Voltage
VIL
V
80
Shutdown Current
RON
UNITS
4.5
VIN = +3.3V
ILATCH
On-Resistance (Note 3)
MAX
VON = VIN, IOUT = 0, switch on
Latch-Off Current
Reverse Current Limit
TYP
2.0
VON = VIN, after an overcurrent
fault (MAX4795/MAX4797) (Note 2)
Forward Current Limit
MIN
+1
0.01
µA
µA
0.2
0.4
0.18
0.36
FLAG Output Logic Low Voltage
ISINK = 1mA
FLAG Output High Leakage
Current
VIN = V F LAG = VON = 4.5V
µA
1
MAX4797/MAX4798, ILOAD = 100mA
VIN > 3.6V
mA
1
MAX4795/MAX4796, ILOAD = 100mA
VIN = +2V to +3.6V
mA
1.4
Ω
V
2
0.5
V
0.4
V
1
µA
Thermal Shutdown
150
°C
Thermal-Shutdown Hysteresis
15
°C
µs
DYNAMIC
Turn-On Time
VON from low to high; IOUT = 10mA, CL = 0.1µF (Note 4)
120
Turn-Off Time
VON from high to low; IOUT = 10mA, CL = 0.1µF (Note 4)
100
Blanking Time
tBLANK
Short-Circuit Current-Limit
Response Time
Retry Time
Overcurrent fault; Figures 2, 3
14
VON = VIN, short circuit applied to OUT
tRETRY
MAX4796/MAX4798, Figure 2 (Note 5)
ns
60
5
210
ms
µs
900
ms
All parts are 100% tested at +25°C. Electrical limits across the full temperature range are guaranteed by design and correlation.
Latch-off current does not include the current flowing into FLAG.
TDFN packages are guaranteed by design.
The on-time is defined as the time taken for the current through the switch to go from 0mA to full load. The off-time is defined as
the time taken for the current through the switch to go from full load to 0mA.
Note 5: Retry time is typically 15 times the blanking time.
2 _______________________________________________________________________________________
Note 1:
Note 2:
Note 3:
Note 4:
450mA/500mA Current-Limit Switches
80
60
40
9
LATCH-OFF CURRENT (µA)
100
VON = VIN
90
SUPPLY CURRENT (µA)
120
10
MAX4795 toc02
VON = VIN
140
80
70
7
6
5
4
3
1
0
0
50
2.5
3.0
3.5
4.0
4.5
-40
-15
35
60
-15
10
35
60
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
SHUTDOWN LEAKAGE CURRENT
vs. TEMPERATURE
LATCH-OFF LEAKAGE CURRENT
vs. TEMPERATURE
0.1
0.01
1
0.1
0.01
0.001
0.001
-15
10
35
60
-15
SHUTDOWN REVERSE LEAKAGE CURRENT
vs. TEMPERATURE
0.1
0.01
0.001
60
85
-40
-15
10
35
TEMPERATURE (°C)
NORMALIZED ON-RESISTANCE
vs. TEMPERATURE
OUTPUT CURRENT
vs. OUTPUT VOLTAGE
MAX4795 toc08
1.0
0.8
0.6
0.4
60
1000
900
800
OUTPUT CURRENT (mA)
0.01
35
1.2
NORMALIZED RON (Ω)
0.1
10
1.4
MAX4795 toc07
1
1
TEMPERATURE (°C)
TEMPERATURE (°C)
VON = 0V, VOUT = 4.5V
10
0.0001
-40
85
100
85
MAX4795 toc06
VON = 0V, VOUT = 0V
LATCH-OFF LEAKAGE CURRENT (nA)
MAX4795 toc04
1
10
MAX4795 toc05
TEMPERATURE (°C)
10
-40
-40
85
TEMPERATURE (°C)
100
10
10
SUPPLY VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT (nA)
2.0
SHUTDOWN SUPPLY CURRENT (nA)
8
2
60
20
SHUTDOWN LEAKAGE CURRENT (nA)
VON = VIN
700
85
MAX4795 toc09
SUPPLY CURRENT (µA)
100
MAX4795 toc01
160
LATCH-OFF CURRENT
vs. TEMPERATURE
SUPPLY CURRENT vs. TEMPERATURE
MAX4795 toc03
QUIESCENT SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX4797/MAX4798
600
500
400
MAX4795/MAX4796
300
200
0.001
0.2
100
0
0
0.0001
-40
-15
10
35
TEMPERATURE (°C)
60
85
-40
-15
10
35
TEMPERATURE (°C)
60
85
0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 3.3
VIN - VOUT (V)
_______________________________________________________________________________________
3
MAX4795–MAX4798
Typical Operating Characteristics
(VIN = 3.3V, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VIN = 3.3V, TA = +25°C, unless otherwise noted.)
FORWARD CURRENT LIMIT
vs. SUPPLY VOLTAGE
FLAG-BLANKING TIMEOUT
vs. TEMPERATURE
SWITCH TURN-ON/OFF TIMES
vs. TEMPERATURE
100
TURN-ON/OFF TIMES (µs)
MAX4797/MAX4798
600
575
550
MAX4795/MAX4796
525
ON
10
1
0.1
2.5
3.0
3.5
4.5
4.0
40
35
30
20
0.001
2.0
45
25
OFF
0.01
500
50
MAX4795 toc12
625
ILOAD = 10mA
FLAG-BLANKING TIMEOUT (ms)
OUT = GND
MAX4795 toc11
1000
MAX4795 toc10
650
FORWARD CURRENT LIMIT (mA)
MAX4795–MAX4798
450mA/500mA Current-Limit Switches
-40
-15
10
35
60
-40
85
-15
10
TEMPERATURE (°C)
MAX4797/MAX4798
CURRENT-LIMIT RESPONSE
MAX4797/MAX4798
CURRENT-LIMIT RESPONSE
CURRENT-LIMIT RESPONSE
(OUT SHORTED TO GND)
3V
3.3V
VIN
2V/div
VIN = VON
1V/div
VIN
2V/div
0V
3.3V
VON
2V/div
0V
0V
3.3V
VOUT
2V/div
0V
0V
IOUT
200mA/div
VIN = 3.3V COUT = 1µF
CIN = 1µF VSEL = 3.3V
85
MAX4795 toc15
MAX4795 toc14
3.3V
IOUT
200mA/div
CIN = 1µF
COUT = 1µF
VIN = VON COUT = 1µF
CIN = 1µF
0V
40µs/div
IOUT
5A/div
0V
4µs/div
40µs/div
MAX4797/MAX4798
REVERSE CURRENT LIMIT
SWITCH TURN-ON TIME RESPONSE
MAX4795 toc16
MAX4795 toc17
VIN
2V/div
3V
0V
3V
3V
VIN = 3.3V
VON
1V/div
VOUT
2V/div
0V
0V
IOUT
1A/div
0V
CIN = 1µF
COUT = 1µF
IOUT
10mA/div
0V
200µs/div
4
60
TEMPERATURE (°C)
MAX4795 toc13
0V
35
SUPPLY VOLTAGE (V)
20µs/div
_______________________________________________________________________________________
450mA/500mA Current-Limit Switches
MAX4797/MAX4798
FLAG-BLANKING RESPONSE
(OVERLOAD CONDITION)
SWITCH TURN-OFF TIME RESPONSE
MAX4795 toc18
MAX4795 toc19
3.3V
3.3V
VON
1V/div
VIN
2V/div
0V
3.3V
VOUT
2V/div
0V
3.3V
0V
IOUT
10mA/div
0V
VFLAG
2V/div
0V
VIN = 3.3V
CIN = 1µF
COUT = 1µF
0V
40ns/div
IOUT
500mA/div
10ms/div
Pin Description
PIN
SOT23
TDFN
NAME
FLAG
1
1
IN
2
5
GND
3
4
6
4
REVERSE-CURRENT
DETECTOR
FUNCTION
BLANKING TIME
CIRCUITRY
Input. Bypass with a 0.1µF ceramic
capacitor to ground.
Ground
ON
Active-High Switch On Input. A logic
high turns the switch on.
FLAG
Fault Output. This open-drain output
goes low when the device stays in
forward or reverse current limit for
more than the blanking time period.
FLAG is high impedance when a fault
is not present or when ON is low.
5
2
OUT
Switch Output. Bypass with a 0.1µF
ceramic capacitor to ground.
—
3
N.C.
No Connection. Not internally
connected.
FORWARD-CURRENT
DETECTOR
N
IN
OUT
ON
GND
LOGIC
AUTORETRY
MAX4795–MAX4798
Figure 1. Functional Diagram
_______________________________________________________________________________________
5
MAX4795–MAX4798
Typical Operating Characteristics (continued)
(VIN = 3.3V, TA = +25°C, unless otherwise noted.)
MAX4795–MAX4798
450mA/500mA Current-Limit Switches
Detailed Description
FLAG Indicator
The MAX4795–MAX4798 are forward/reverse currentlimited switches that operate from a 2V to 4.5V input
voltage range and guarantee a 450mA and 500mA
minimum current-limit threshold for different options.
The voltage drop across an internal sense resistor is
compared to two reference voltages to indicate a forward or reverse current-limit fault. When the load current exceeds the preset current limit for greater than
the fault-blanking time, the switch opens.
The MAX4795–MAX4798 feature a latched output (FLAG).
Whenever an overcurrent condition is encountered,
the MAX4795/MAX4797 latch FLAG low and turn the
switch off. The MAX4796/MAX4798 latch FLAG low and
keep it low until the overcurrent condition is removed.
During this time, the switch cycles on and off in the
autoretry mode. When the overcurrent condition is
removed, FLAG deasserts and the switch turns on
(Figure 2). FLAG is an open-drain output transistor and
requires an external pullup resistor from FLAG to IN.
During shutdown (ON is low), the pulldown on FLAG
output is released to limit power dissipation. FLAG goes
low when any of the following conditions occur:
• The die temperature exceeds the thermal-shutdown
temperature limit of +150°C.
The MAX4796 and MAX4798 have an autoretry function
that turns on the switch again after an internal retry time
expires. If the faulty load condition is still present after
the blanking time, the switch turns off again and the
cycle is repeated. If the faulty load condition is not present, the switch remains on.
The MAX4795 and MAX4797 do not have the autoretry
option and the switch remains in latch-off mode until
the ON pin or the input power is cycled from high to low
and then high again.
• The device is in current limit for more than the faultblanking period.
• The switch is in autoretry.
Reverse-Current Protection
tBLANK
The MAX4795–MAX4798 limit the reverse current (VOUT
to VIN) from exceeding the maximum IREV value. The
switch is shut off and FLAG is asserted if the reverse
current-limit condition persists for more than the blanking
time. This feature prevents excessive reverse currents
from flowing through the device.
Switch-On/Off Control
Toggle ON high to enable the current-limited switches.
The switches are continuously on if there is no fault.
When a forward/reverse current fault is present or the die
exceeds the thermal-shutdown temperature of +150°C,
OUT is internally disconnected from IN and the supply
current decreases to 8µA (latch off). The switch is now
operating in one of its off states. The switch-off state also
occurs when driving ON low, thus reducing the supply
current (shutdown) to 0.01µA. Table 1 illustrates the
ON/OFF state of the MAX4795–MAX4798 current-limit
switches.
tRETRY
tBLANK
tBLANK
CURRENT
LIMIT
SHORT
CONDITION
REMOVED
ON
SWITCH
STATUS
OFF
FLAG PIN
STATUS
Figure 2. MAX4796/MAX4798 Autoretry Fault-Blanking Diagram
Table 1. MAX4795–MAX4798 Switch Truth Table
6
ON
FAULT
Low
X
High
Thermal
High
Current limit
SWITCH ON/OFF
SUPPLY CURRENT MODE
OFF
Shutdown
OFF immediately (tBLANK period does not apply)
Latchoff
OFF after tBLANK period has elapsed
Latchoff
ON during tBLANK period, OFF during tRETRY period for the
MAX4796 and MAX4798; cycle repeats until fault is removed
See the Autoretry section
_______________________________________________________________________________________
450mA/500mA Current-Limit Switches
Latchoff (MAX4795/MAX4797)
When the forward or reverse current-limit threshold is
exceeded, tBLANK timer begins counting. The timer
resets if the overcurrent condition disappears before
tBLANK has elapsed. The switch is shut off and FLAG
asserts if the overcurrent condition continues up to the
end of the blanking time. Reset the switch by either toggling ON (Figure 3) or cycling the input voltage.
Fault Blanking
The MAX4795–MAX4798 feature 14ms (min) fault blanking. Fault blanking allows current-limit faults, including
momentary short-circuit faults that occur when hot
swapping a capacitive load, and also ensures that no
fault is issued during power-up. When a load transient
causes the device to enter current limit, an internal
counter starts. If the load-transient fault persists beyond
the fault-blanking timeout, FLAG asserts low. Load-transient faults less than tBLANK do not cause a FLAG output assertion. Only current-limit faults are blanked.
A thermal fault causes FLAG to assert immediately and
does not wait for the blanking time.
Thermal Shutdown
The MAX4795–MAX4798 have a thermal-shutdown feature to protect the devices from overheating. The switch
tBLANK
MAX4795–MAX4798
Autoretry (MAX4796/MAX4798)
When the forward or reverse current-limit threshold is
exceeded, tBLANK timer begins counting (Figure 2).
The timer resets if the overcurrent condition disappears
before tBLANK has elapsed. A retry time delay, tRETRY,
is started immediately after tBLANK has elapsed and
during that time, the switch is latched off and FLAG
asserts. At the end of tRETRY, the switch is turned on
again. If the fault still exists, the cycle is repeated. If the
fault has been removed, the switch stays on and FLAG
deasserts.
The autoretry feature saves system power in the case
of an overcurrent or short-circuit condition. During
tBLANK, when the switch is on, the supply current is at
the current limit. During tRETRY, when the switch is off,
the current through the switch is zero. Instead of
observing the full load current, the switch sees the
equivalent load current times duty cycle or ISUPPLY =
I LOAD ✕ t BLANK /(t BLANK + t RETRY ). With a typical
tBLANK = 37ms and typical tRETRY = 555ms, the duty
cycle is 6%, which results in a 94% power savings over
the switch being on the entire time. The duty cycle is
consistent across the process and devices.
tBLANK
LOAD
CURRENT
ON
SWITCH
STATUS
OFF
ON PIN
VOLTAGE
FLAG PIN
STATUS
(a)
tBLANK
tBLANK
LOAD
CURRENT
ON
SWITCH
STATUS
OFF
IN PIN
VOLTAGE
FLAG PIN
STATUS
Figure 3. MAX4795/MAX4797 Latch-Off Fault Blanking
turns off and FLAG goes low immediately (no fault
blanking) when the junction temperature exceeds
+150°C. The switches with autoretry turn back on when
the device temperature drops approximately 15°C. The
switches with latchoff require ON cycling.
Applications Information
Input Capacitor
To limit the input voltage drop during momentary output
short-circuit conditions, connect a capacitor from IN to
GND. A 0.1µF ceramic capacitor is adequate for most
applications; however, higher capacitor values further
reduce the voltage drop at the input and are recommended for lower voltage applications.
_______________________________________________________________________________________
7
MAX4795–MAX4798
450mA/500mA Current-Limit Switches
Output Capacitance
Connect a 0.1µF capacitor from OUT to GND. This
capacitor helps prevent inductive parasitics from
pulling OUT negative during turn off, thus preventing
the MAX4795–MAX4798 from tripping erroneously. If
the load capacitance is too large, then current may not
have enough time to charge the capacitor and the
device assumes that there is a faulty load condition.
The maximum capacitive load value that can be driven
from OUT is obtained by the following formula:
CMAX <
IFWD _ MIN × tBLANK _ MIN
VIN
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 (no more than 5mm).
IN and OUT pins must be connected with short traces
to the power bus.
Selector Guide
PART
CURRENT LIMIT
(mA)
PMAX =
VIN _ MAX × IOUT _ MAX × tBLANK
tRETRY + tBLANK
450
No
MAX4795ETT
450
No
MAX4796EUK-T
450
Yes
MAX4796ETT
450
Yes
MAX4797EUK-T
500
No
MAX4797ETT
500
No
MAX4798EUK-T
500
Yes
MAX4798ETT
500
Yes
= 211mW
where VIN = 4.5V, IOUT = 750mA, tBLANK = 14ms, and
tRETRY = 210ms.
Attention must be given to the MAX4795 and MAX4797
where the latchoff condition must be manually reset by
toggling ON from high to low. If the latchoff time duration is not sufficiently high, it is possible for the device
to reach the thermal-shutdown threshold and never be
able to turn the device on until it cools down.
Chip Information
TRANSISTOR COUNT: 2539
PROCESS: BiCMOS
AUTORETRY
MAX4795EUK-T
8
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:
_______________________________________________________________________________________
450mA/500mA Current-Limit Switches
SOT-23 5L .EPS
PACKAGE OUTLINE, SOT-23, 5L
21-0057
E
1
1
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 _____________________ 9
© 2003 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
MAX4795–MAX4798
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
Similar pages