Micrel MIC2537-1BM Quad power distribution switch quad power distribution switch Datasheet

MIC2537
Micrel
MIC2537
Quad Power Distribution Switch
Final Information
General Description
Features
The MIC2537 is a cost-effective high-side power switch with
four independently controlled channels, optimized for buspowered Universal Serial Bus (USB) applications. Few external components are necessary to satisfy USB requirements.
The MIC2537 satisfies the following USB requirements: each
switch channel supplies up to 100mA as required by USB
bus-powered downstream devices; fault current is limited to
typically 250mA, well below the UL 25VA safety requirements; and a flag output is available to indicate fault conditions to the local USB controller. Soft start eliminates the
momentary voltage drop on the upstream port that may occur
when the switch is enabled in bus-powered applications.
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Additional features include thermal shutdown to prevent
catastrophic switch failure from high-current loads and 3.3V
and 5V logic compatible enable inputs.
The MIC2537 is available in active-high and active-low versions in a 16-lead SOP package.
Compliant to USB specifications
3V to 5.5V input
100mA minimum continuous load current per port
425mΩ typical on-resistance
< 400mA current limit
Individual open-drain fault flag leads
3V/5V-compatible enable inputs
Active-high (-1) and active-low (-2) versions
100µA max. on-state supply current
<1µA typical off-state supply current
16-lead SOP package
–40°C to 85°C operation
Applications
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USB keyboards
USB bus-powered docking stations
Notebook docking stations
Notebook PCs
PDA
General power distribution
Typical Application
Upstream VBUS
4.75V to 5.25V
500mA max.
Ferrite
Bead
10k
MIC5207-3.3
LDO Regulator
IN
4.7
µF
3.3V USB Controller
EN
OC
V+
OUT
1µF
GND
EN
OC
EN
D+
D–
Bold lines indicate
0.1" wide, 1-oz. copper
high-current traces.
VBUS
10k 10k 10k
GND
ENA
0.01µF
IN
FLGA
ENB
NC
OUTA
FLGB
OUTB
OUTC
ENC
OC
FLGC
EN
END
OC
FLGD
D+
33µF*
MIC2537
D–
GND
0.1
µF
VBUS
D+
33µF*
0.01µF
OUTD
Downstream
USB
Port 1
100mA max.
D–
GND
NC
Downstream
USB
Port 2
100mA max.
GND
VBUS
D+
33µF*
0.01µF
* 33µF, 16V tantalum or 100µF, 10V electrolytic per port
D–
GND
Downstream
USB
Port 3
100mA max.
VBUS
D+
33µF*
0.01µF
D–
GND
Downstream
USB
Port 4
100mA max.
Typical Bus-Powered Hub
UL Recognized Component
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
December 1999
1
MIC2537
MIC2537
Micrel
Ordering Information
Part Number
Enable
Temperature Range
Package
MIC2537-1BM
Active High
–40°C to +85°C
16-Lead SOP
MIC2537-2BM
Active Low
–40°C to +85°C
16-Lead SOP
Pin Configuration
MIC2537-x
FLGA
1
16 FLGD
ENA
2
15 END
OUTA
3
14 OUTD
GND
4
13 IN
NC
5
12 NC
OUTB
6
11 OUTC
ENB
7
10 ENC
FLGB
8
9
FLGC
16-Lead SOP (M)
Pin Description
Pin Number
Pin Name
1
FLGA
Flag A: (Output): Channel A open-drain fault flag output.
2
ENA
Enable A (Input): Channel A control input.
3
OUTA
Output A: Channel A switch output.
4
GND
Ground: Supply return. Connect both leads to ground.
5, 12
NC
6
OUTB
7
ENB
Enable B (Input): Channel B control input.
8
FLGB
Flag B (Output): Channel B open-drain fault flag output.
9
FLGC
Flag C (Output): Channel C open-drain fault flag output.
10
ENC
Enable C (Input): Channel C control input.
11
OUTC
13
IN
14
OUTD
15
END
Enable D (Input): Channel D control input.
16
FLGD
Flag D (Output): Channel D open-drain fault flag output.
December 1999
Pin Function
Not internally connected
Output B: Channel B switch output.
Output C: Channel C switch output.
Positive Supply Input
Output D: Channel D switch output.
2
MIC2537
MIC2537
Micrel
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltage (VIN) .....................................................+6V
Fault Flag Voltage (VFLG) .............................................. +6V
Fault Flag Current (IFLG) ............................................ 25mA
Output Voltage (VOUT) .................................................. +6V
Output Current (IOUT) ............................... Internally Limited
Control Input (VEN) ......................................... –0.3V to 12V
Storage Temperature (TS) ....................... –65°C to +150°C
Lead Temperature (Soldering 5 sec.) ....................... 260°C
ESD Rating, Note 3 ....................................................... 2kV
Supply Voltage (VIN) ...................................... +3V to +5.5V
Ambient Operating Temperature (TA) ........ –40°C to +85°C
Thermal Resistance
SOP (θJA) .......................................................... 120°C/W
Electrical Characteristics
VIN = +5V; TA = 25°C; unless noted.
Parameter
Condition
Supply Current
Note 4, switch off, OUTA–D = open
Enable Input Threshold
Min
Typ
Max
Units
0.75
5
µA
Note 4, all switches on, OUTA–D = open
70
100
µA
low-to-high transition
1.8
2.4
V
high-to-low transition, Note 4
Enable Input Current
0.8
1.6
V
VEN = VOH(min) = 2.4V
0.01
1
µA
VEN = VOL(max) = 0.8V
0.01
1
µA
Enable Input Capacitance
1
pF
Switch Resistance
single switch, 100mA load
425
Output Turn-On Delay
RL = 50Ω, CL = 1µF, Note 5
0.51
ms
Output Turn-On Rise Time
RL = 50Ω, CL = 1µF, Note 5
0.5
ms
Output Turnoff Delay
RL = 50Ω, CL = 1µF, Note 5
150
300
µs
Output Turnoff Fall Time
RL = 50Ω, CL = 1µF, Note 5
148
300
µs
Output Leakage Current
each output (switch off)
1
10
µA
Current Limit Threshold
ramped load applied to enable output, Note 6
300
500
mA
Continuous Load Current
each output, FLG not active
100
Short Circuit Current Limit
each output (enabled into load), VOUT = 4.0V
150
Overtemperature Shutdown
TJ increasing
135
°C
Threshold
TJ decreasing
125
°C
Error Flag Output Resistance
VIN = 5V, IL = 10mA
10
Ω
VIN = 3.3V, IL = 10mA
12
Ω
Error Flag Off Current
0.2
VFLAG = 5V
Exceeding the absolute maximum rating may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
mΩ
mA
250
0.01
Note 1.
700
400
mA
µA
1
Note 3.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF.
Note 4.
Off is ≤ 0.8V and on is ≥ 2.4V for the MIC2537-1. Off is ≥ 2.4V and on is ≤ 0.8V for the MIC2537-2. The enable input has approximately
200mV of hysteresis. See control threshold charts.
Note 5.
See “Timing Diagrams.”
Note 6.
See “Functional Characteristics: Current-Limit Response” graph.
December 1999
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MIC2537
MIC2537
Micrel
Typical Characteristics
100
60
40
TA = 25°C
RL = ∞
3
4
5
SUPPLY VOLTAGE (V)
60
40
250
CURRENT (mA)
ON RESISTANCE (mΩ)
400
300
200
VIN = 5V
IL = 100mA
0
2
Control Threshold
vs. Supply Voltage
2.0
2.0
1.5
VIL
1.0
1.5
TIME (µs)
THRESHOLD VOLTAGE (V)
ENABLE VOLTAGE (V)
VIH
0
TA = 25°C
2
3
4
5
SUPPLY VOLTAGE (V)
ILIM
100
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
6
TA = 25°C
IL = 100mA
100
3
4
5
SUPPLY VOLTAGE (V)
250
200
3
4
5
SUPPLY VOLTAGE (V)
6
ITHR
200
ILIM
150
100
TA = 25°C
50
200
300
ITHR
150
300
Overcurrent Threshold and
Current Limit vs. Temperature
Overcurrent Threshold and
Current Limit vs. Supply Voltage
300
400
0
2
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
6
500
0.5
RL = ∞
20
Output On-Resistance
Variation vs. Temperature
100
VIN = 3.3V
CURRENT (mA)
2
VIN = 5V
VIN = 5V
50
0
-40 -20
6
0
20
40
60
80 100
TEMPERATURE (°C)
Control Threshold
vs. Temperature
Output Rise Time
vs. Temperature
500
VIH
400
1.5
VIL
1.0
0.5
VIN = 5V
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
TIME (µs)
20
80
ON-RESISTANCE (mΩ)
80
0
Ouput On-Resistance
Variation vs. Supply Voltage
500
100
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
Supply Current
vs. Temperature
Supply Current
vs. Supply Voltage
300
200
100
VIN = 5V
CL = 0.01µF
RL = 44Ω
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
Output Fall Time
vs. Temperature
1.0
0.5
VIN = 5V
CL = 0.01µF
RL = 44Ω
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
December 1999
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MIC2537
MIC2537
Micrel
Functional Characteristics
Input Voltage Response
(Input Voltage Decreasing: MIC2537-2)
VOUT
VFLG
VIN
IOUT
(100mA/div.) (2V/div.) (2V/div.) (2V/div.)
VOUT
VFLG
VIN
IOUT
(100mA/div.) (2V/div.) (2V/div.) (2V/div.)
Input Voltage Response
(Input Voltage Rising: MIC2537-2)
EN = 0V
RL = 24Ω
EN = 0V
RL = 24Ω
Current Limit Transient Response
(Heavy Load Applied to Output: MIC2537-2)
Current Limit Response
(Ramped Load: MIC2537-2)
VOUT
VFLG
VEN
(5V/div.) (10V/div.)(5V/div.)
TIME (25ms/div.)
VOUT
VFLG
VEN
(5V/div.) (10V/div.)(5V/div.)
TIME (25ms/div.)
1V
TIME (25µs/div.)
December 1999
250mA
Current Limit
Threshold
IOUT
(100mA/div.)
IOUT
(500mA/div.)
VIN = 5V
1V
180mA
Short Circuit
Current Limit
VIN = 5V
TIME (5ms/div.)
5
MIC2537
MIC2537
Micrel
Test Circuit
VOUT
Device
Under OUT
Test
RL
CL
Timing Diagrams
tR
tF
90%
VOUT
90%
10%
10%
Output Rise and Fall Times
VEN
50%
tOFF
tON
90%
VOUT
10%
Active-Low Switch Delay Times (MIC2537-2)
VEN
50%
tOFF
tON
VOUT
90%
10%
Active-Low Switch Delay Times (MIC2537-1)
December 1999
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MIC2537
MIC2537
Micrel
Functional Diagram
FLGA
OUTA
ENA
GATE
CONTROL
CHARGE
PUMP
CURRENT
LIMIT
FLG B
ENB
OUTB
GATE
CONTROL
CHARGE
PUMP
CURRENT
LIMIT
1.2V
REFERENCE
THERMAL
SHUTDOWN
OSC.
IN
CURRENT
LIMIT
CHARGE
PUMP
GATE
CONTROL
ENC
OUTC
FLGC
CHARGE
PUMP
CURRENT
LIMIT
GATE
CONTROL
END
OUTD
FLGD
MIC2537
GND
December 1999
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MIC2537
MIC2537
Micrel
Functional Description
Current Sensing and Limiting
The MIC2537-1 and MIC2537-2 are quad high-side switches
with active-high and active-low enable inputs, respectively.
Fault conditions turn off or inhibit turn-on of one or more of the
output transistors, depending upon the type of fault, and
activate the open-drain error flag transistors making them
sink current to ground.
Input and Output
The current-limit threshold is preset internally. The preset
level prevents damage to the output MOSFET and external
load but allows a minimum current of 0.15A through the
output MOSFET of each channel.
The current-limit circuit senses a portion of the output FET
switch current. The current sense resistor shown in the block
diagram is virtual and has no voltage drop. The reaction to an
overcurrent condition varies with the following three scenarios:
IN (input) is the power supply connection to the logic circuitry
and the drain of each output MOSFET. OUTx (output) is the
source of each respective MOSFET. In a typical circuit,
current flows through the switch from IN to OUTx toward the
load. If VOUT is greater than VIN, current will flow from OUT
to IN since the MOSFET is bidirectional when on.
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 (VOUTx > VIN) when the output is off. In
this situation, the MIC2537 prevents reverse current flow.
Switch Enabled into Short Circuit
If a switch is powered on or enabled into an excessive load or
short circuit, the switch immediately goes into a constantcurrent mode, slowly increasing the output voltage. The fault
flag goes low until the load is reduced.
Short Circuit Applied to Output
When a heavy load or short circuit is applied to an enabled
switch, a large transient current may flow until the currentlimit circuitry responds. Once this occurs, the device limits
current to less than the short circuit current-limit specification.
See the “Functional Characteristics: Current-Limit Transient
Response graph for details.
Current-Limit Response
The MIC2537 current-limit profile exhibits a small foldback
effect of approximately 100mA. Once this current-limit threshold is exceeded the device enters constant-current mode.
This constant current is specified as the short-circuit current
limit in the “Electrical Characteristics” table. It is important to
note that the MIC2537 will deliver load current up to the
current-limit threshold. See the “Functional Characteristics:
Current-Limit Response” graph for details.
Fault Flag
FLGx is an open-drain N-channel MOSFET output. Fault
flags are active (low) for current limit or thermal shutdown.
Each flag output MOSFET is capable of sinking a 10mA load
to approximately 200mV above ground. Several FLGx pins
may be wired-NOR connected to a common pull-up resistor.
Thermal Shutdown
Thermal shutdown shuts off the affected output MOSFET
and signals the corresponding fault flags if the die temperature exceeds 135°C. 10°C of hysteresis prevents the switch
from turning on until the die temperature drops to 125°C.
Overtemperature detection functions only when at least one
switch is enabled.
Current-Limit Induced Thermal Shutdown
Internal circuitry increases the output MOSFET on-resistance until the series combination of the MOSFET on-resistance and the load impedance limits output current to approximately 200mA. The resulting increase in power dissipation may cause the shorted channel to go into thermal
shutdown. In addition, even though individual channels are
thermally isolated, it is possible they may shut down when an
adjacent channel is shorted. When this is undesirable, shutdown of the channels not shorted can be avoided by externally responding to the fault and disabling the current limited
channel before the shutdown temperature is reached. The
delay between the flag indication of a current limit fault and
thermal shutdown will vary with ambient temperature, board
layout, and load impedance, but is typically several seconds.
The USB controller must therefore recognize a fault and
disable the appropriate channel within this time.
December 1999
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MIC2537
MIC2537
Micrel
In USB applications it is required that output bulk capacitance
shown in “Typical Application” is utilized to meet transient
regulation requirements during hot-plug events. When the
MIC2537 is enabled, the flag will go active for about 5ms
depending on output capacitance. Additionally, during hotplug events, inrush currents may cause the flag to go active
for approximately 30µs. If these “false” overcurrent indications are a system problem, they can be masked by an RC
filter on the flag output (see Figure 2). Alternatively, a 15ms
debounce routine may be programmed into the USB logic
controller to eliminate the need for an RC filter.
Applications Information
Supply Filtering
A 0.1µF to 1µF bypass capacitor from IN to GND, located at
the device, 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.
Input or output transients must not exceed the absolute
maximum supply voltage (VIN(max) = 6V) even for a short
duration.
VIN
3V to 5.5V
0.1µF to 1µF
Bus-Powered Hub Port Switching
The USB Specification requires that bus-powered hubs implement port switching on either a ganged or individual basis.
The specific implementation must be reported via the Hub
Descriptor Status Register. Individual port switching has
advantages in that a fault on one port will not prevent the other
ports from operating correctly. In addition, a soft-start circuit
must be included in order to reduce inrush currents when the
switch is enabled. To meet this requirement, the MIC2537
has been designed to slowly ramp its output.
MIC2537
FLGA
FLGB
ENA
ENB
OUTA OUTB
GND
NC
IN
NC
OUTC OUTD
ENC
END
FLGC
FLGD
Suspend Current
For hubs, Universal Serial Bus Specification Revision 1.1
section 7.2.3, stipulates that the maximum suspend current
for a configured hub is 2.5mA. This number is derived by
allocating 500µA for up to four downstream ports plus 500µA
for the hub’s internal functions. A nonconfigured hub is
considered a low-power device and cannot consume more
than 500µA. In a nonconfigured state all downstream devices
will be switched off. In most cases, a nonconfigured hub is not
a practical state for the system. Therefore, the 2.5mA specification is the applicable target specification for the suspend
state. In a bus-powered hub with less than 4 ports, the hub
may use the additional current for internal functions.
Figure 1. Supply Bypassing
Enable Input
EN must be driven logic high or logic 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.
Soft Start
The MIC2537 presents a high impedance when off and slowly
becomes a low impedance as it turns on. This reduces inrush
current and related voltage drop that results from charging a
capacitive load, satisfying the USB voltage droop requirements.
The 500µA worst case suspend current must be further
divided among the data port termination resistors and internal
functions. The termination resistors will consume
3.6V ÷ (16.5KΩ – 5%) = 230µA. This leaves only 270µA for
internal functions. Assuming 100µA as the maximum USB
controller suspend current, 170µA remains for the rest of the
system. The MIC2537 will consume 100µA maximum, leaving a margin of 70µA.
Transient Overcurrent Fault-Flag Filter
When the MIC2537 is enabled, large values of capacitance
at the output of the device will cause inrush currents to flow
that exceed the short circuit current-limit threshold of the
device and cause the flag to activate. The duration of this time
depends on the size of the output capacitance. See “Functional Characteristics: Switch Turn-On and Turnoff
Charcteristics” for details. During the charging time, the
device enters into constant-current mode and the flag is
activated. As the capacitance is charged the current decreases below the short circuit current-limit threshold and the
flag will be deasserted.
USB Controller
OVERCURRENT
10k
FLGA
50k
0.3µF
FLGB
FLGC
FLGD
Figure 2. Transient Filter
December 1999
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MIC2537
MIC2537
Micrel
USB Voltage Regulation
Overcurrent Indication
USB specifications require a minimum downstream voltage
supply of 4.40V from a bus-powered hub port (See Application Note 17 for details). The USB specification allows for a
100mV drop across the hub, leaving 250mV for PCB, upstream cable, and connector resistance. Therefore, the onresistance of the switch for each port, not including PCB
resistance, must be about 100mV ÷ 100mA = 1Ω. The
MIC2537 has a maximum on-resistance of 700mΩ, which
easily satisfies this requirement.
The USB Specification does not require bus-powered hubs to
report overcurrent conditions to the host since the hub is
already current-limited at the upstream port. However, if it is
desired to report overcurrent, the Hub Descriptor Status
Register must be programmed to indicate this. The MIC2537
provides a flag output for this application.
December 1999
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MIC2537
MIC2537
Micrel
Package Information
PIN 1
0.157 (3.99)
0.150 (3.81)
DIMENSIONS:
INCHES (MM)
0.020 (0.51)
REF
0.050 (1.27)
BSC
0.0648 (1.646)
0.0434 (1.102)
0.020 (0.51)
0.013 (0.33) 0.0098 (0.249)
0.0040 (0.102)
0.394 (10.00)
0.386 (9.80)
SEATING
PLANE
45°
0°–8°
0.050 (1.27)
0.016 (0.40)
0.244 (6.20)
0.228 (5.79)
16-Lead SOP (M)
December 1999
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MIC2537
MIC2537
Micrel
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
WEB
USA
http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
© 1999 Micrel Incorporated
December 1999
12
MIC2537
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