January 2000
1
MIC2525
MIC2525
Micrel
MIC2525
USB Power Control Switch
Not Recommended for New Designs
Refer to MIC2025
General Description
The MIC2525 is an integrated high-side power switch, opti-
mized for self-powered and bus-powered Universal Serial
Bus (USB) applications. Few external components are nec-
essary to satisfy USB requirements.
The MIC2525 satisfies the following USB requirements: each
switch channel supplies up to 500mA as required by USB
downstream devices; the switch's low on-resistance meets
USB voltage drop requirements; fault current is limited to
typically 750mA, well below the UL 25VA safety require-
ments; and a flag output is available to indicate fault condi-
tions 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.
Additional features include thermal shutdown to prevent
catastrophic switch failure from high-current loads,
undervoltage lockout (UVLO) to ensure that the device re-
mains off unless there is a valid input voltage present, and
3.3V and 5V logic compatible enable inputs.
The MIC2525 is a UL recognized component and is available
in active-high and active-low versions in 8-pin DIP and SOIC
packages.
For new designs, please see the MIC2025/2075.
Typical Application
V
BUS
D+
D
GND
USB
Port
Data
EN
OUT
FLG
IN
ON/OFF
OVERCURRENT
MIC2525-2
3.3V USB Controller
GND
OUT
NC
V
CC
5.0V
0.1F
10k
MIC5207-3.3
IN
OUT
GND
4.50V to 5.25V
Upstream V
BUS
100mA max.
Ferrite
Beads
150F
V
BUS
D+
D
GND
Data
1F
1F
100k
VIN
GND
3.3V
NC
Single-Port USB Self-Powered Hub
Features
Compliant to USB specifications
UL Recognized Component
3V to 5.5V input
500mA minimum continuous load current per port
140m
maximum on-resistance
1.25A maximum short circuit current limit
Open-drain fault flag pins
110
A typical on-state supply current
1
A typical off-state supply current
Output can be forced higher than input (off-state)
Thermal shutdown
2.4V typical undervoltage lockout (UVLO)
1ms turn-on (soft-start) and fast turnoff
Active-high or active-low enable versions
8-pin SOIC and DIP packages
Applications
USB hosts and self-powered hubs
USB bus-powered hubs
Hot plug-in power supplies
Battery-charger circuits
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
MIC2525
Micrel
MIC2525
2
January 2000
Pin Description
Pin Number
Pin Name
Pin Function
1
EN
Enable (Input): Logic-compatible enable input. High input > 2.1V typical.
Low input <1.9V typical (-1 active high, -2 active low).
2
FLG
Fault Flag (Output): Active-low, open-drain output. Indicates overcurrent,
UVLO and thermal shutdown.
3
GND
Ground: Supply return.
4, 5
NC
Not internally connected. (For pin compatibility with the MIC2505, connect
pin 7 to pin 5 and leave pin 4 unconnected.)
7
IN
Supply Input: Output MOSFET drain. Also supplies IC's internal circuitry.
Connect to positive supply.
6, 8
OUT
Switch Output: Output MOSFET source. Typically connect to switched side
of load.
Pin Configuration
1
2
3
4
8
7
6
5
OUT
IN
OUT
NC
EN
FLG
GND
NC
MIC2525
8-Pin SOIC (M)
8-Pin DIP (N)
LOGIC,
CHARGE
PUMP
6, 8 (OUT)
3 (GND)
(EN) 1
(FLG) 2
7 (IN)
MIC2525
Ordering Information
Part Number
Enable
Temperature Range
Package
MIC2525-1BM
Active High
40
C to +85
C
8-Pin SOIC
MIC2525-2BM
Active Low
40
C to +85
C
8-Pin SOIC
MIC2525-1BN
Active High
40
C to +85
C
8-pin DIP
MIC2525-2BN
Active Low
40
C to +85
C
8-pin DIP
January 2000
3
MIC2525
MIC2525
Micrel
Electrical Characteristics
V
IN
= +5V; T
A
= 25
C; unless noted.
Parameter
Condition
Min
Typ
Max
Units
Supply Current
Note 4, switch off, OUT = open
0.75
5
A
Note 4, switch on, OUT = open
110
160
A
Enable Input Threshold
low-to-high transition
2.1
2.4
V
high-to-low transition, Note 4
0.8
1.9
V
Enable Input Current
V
EN
= 0V to 5.5V
1
0.01
1
A
Enable Input Capacitance
1
pF
Switch Resistance
V
IN
= 5V, I
OUT
= 500mA
100
140
m
V
IN
= 3.3V, I
OUT
= 500mA
140
180
m
Output Turn-On Delay
R
L
= 10
each output
0.5
ms
Output Turn-On Rise Time
R
L
= 10
each output
1
ms
Output Turnoff Delay
R
L
= 10
each output
1
20
s
Output Turnoff Fall Time
R
L
= 10
each output
1
20
s
Output Leakage Current
output disabled
10
A
Continuous Load Current
0.5
A
Short-Circuit Current Limit
enable into load, V
OUT
= 4.0V
0.5
0.75
1.25
A
Current-Limit Threshold
ramped load applied to enabled output, V
OUT
4.0V, Note 5
1.6
2.2
A
Overtemperature Shutdown
T
J
increasing
135
C
Threshold
T
J
decreasing
125
C
Error Flag Output Resistance
V
IN
= 5V, I
L
= 10mA
10
25
V
IN
= 3.3V, I
L
= 10mA
15
40
Error Flag Off Current
V
FLAG
= 5V
0.01
1
A
UVLO Threshold
V
IN
= increasing
2.5
V
V
IN
= decreasing
2.3
V
Note 1.
Exceeding the absolute maximum rating may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
Note 4.
Off is
0.8V and on is
2.4V for the MIC2525-1. Off is
2.4V and on is
0.8V for the MIC2525-2. The enable input has approximately
200mV of hysteresis. See control threshold charts.
Note 5.
See "Functional Characteristics: Current-Limit Response" photo.
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
IN
) ..................................................... +6V
Fault Flag Voltage (V
FLG
) .............................................. +6V
Fault Flag Current (I
FLG
) ............................................ 50mA
Output Voltage (V
OUT
) .................................................. +6V
Output Current (I
OUT
) ............................... Internally Limited
Control Input (V
EN
) ......................................... 0.3V to 12V
Storage Temperature (T
S
) ....................... 65
C to +150
C
Lead Temperature (Soldering 5 sec.) ....................... 260
C
ESD Rating, Note 3 ...................................................... 2kV
Operating Ratings
(Note 2)
Supply Voltage (V
IN
) ...................................... +3V to +5.5V
Ambient Operating Temperature (T
A
) ........ 40
C to +85
C
Thermal Resistance
SOIC (
JA
) ......................................................... 120
C/W
DIP(
JA
) ............................................................. 130
C/W
MIC2525
Micrel
MIC2525
4
January 2000
Typical Characteristics
V
IN
= 5V; T
A
= 25
C; one switch section; unless noted.
80
90
100
110
3.0
3.5
4.0
4.5
5
5.5
OUTPUT RESISTANCE (m
)
SUPPLY VOLTAGE (V)
Output On-Resistance
vs. Supply Voltage
T = 25
C
R
L
= 44
Awaiting Full
Characterization
Data
60
80
100
120
140
-40 -20
0
20
40
60
80 100
ON-RESISTANCE (m
)
TEMPERATURE (
C)
Output On-Resistance
vs. Temperature
R
L
= 44
V
IN
= 5V
1.0
1.5
2.0
2.5
2
3
4
5
THRESHOLD VOLTAGE (V)
SUPPLY VOLTAGE (V)
Control Threshold
vs. Supply Voltage
V
CTL
RISING
V
CTL
FALLING
0
50
100
150
200
-40 -20
0
20
40
60
80 100
SUPPLY CURRENT (
A)
TEMPERATURE (
C)
On-State Supply Current
vs. Temperature
SWITCH ON
0
0.5
1.0
1.5
2.0
-40 -20
0
20
40
60
80 100
SUPPLY CURRENT (
A)
TEMPERATURE (
C)
Off-State Supply Current
vs. Temperature
SWITCH OFF
1.0
1.5
2.0
2.5
-40 -20
0
20
40
60
80 100
ENABLE VOLTAGE (V)
TEMPERATURE (
C)
Control Threshold
vs. Temperature
V
EN
RISING
V
IN
= 5V
V
EN
FALLING
0
1
2
3
4
5
-40 -20
0
20
40
60
80 100
TIME (
s)
TEMPERATURE (
C)
Output Rise Time
vs. Temperature
Awaiting Full
Characterization
Data
0
0.2
0.4
0.6
0.8
1.0
-40 -20
0
20
40
60
80 100
TIME (ms)
TEMPERATURE (
C)
Output Fall Time
vs. Temperature
Awaiting Full
Characterization
Data
1.0
1.2
1.4
1.6
1.8
2.0
-25
0
25
50
75
100
CURRENT (A)
TEMPERATURE (
C)
Current-Limit Threshold
vs. Temperature
SHORT CIRCUIT
CURRENT LIMIT
CURRENT LIMIT
THRESHOLD
1.5
2.0
2.5
3.0
-40 -20
0
20
40
60
80 100
THRESHOLD VOLTAGE (V)
TEMPERATURE (
C)
UVLO Threshold Voltage
vs. Temperature
V
IN
RISING
V
IN
FALLING
0
50
100
150
200
250
0
2
4
6
SUPPLY CURRENT (
A)
SUPPLY VOLTAGE (V)
On-State Supply Current
vs. Supply Voltage
SWITCH ON
0
0.5
1.0
1.5
2.0
2
3
4
5
6
SUPPLY CURRENT (
A)
SUPPLY VOLTAGE (V)
Off-State Supply Current
vs. Supply Voltage
SWITCH OFF
January 2000
5
MIC2525
MIC2525
Micrel
Functional Characteristics
Short Circuit Response
(Short Applied to Output)
TIME (500ms/div.)
I
OUT
(1A/div
.
)
V
OUT
(2V/div
.
)
V
FLG
(5V/div
.
)
Thermal Shutdown
1A Short Circuit Current Limit
Short Circuit Response
Enable into Short Circuit
1.1A Short Circuit
Current-Limiting
TIME (250ms/div.)
I
OUT
(1A/div
.
)
V
EN
(5V/div
.
)
V
FLG
(5V/div
.
)
V
OUT
(2V/div
.
)
Thermal
Shutdown
Input Voltage
Response
2.6V (UVLO) Threshold
TIME (100ns/div.)
I
OUT
(200mA/div
.
)
V
IN
(2V/div
.
)
V
FLG
(5V/div
.
)
V
OUT
(2V/div
.
)
V
EN
= V
IN
R
L
= 35
C
L
= 15
F
Turn-On, Turnoff
Characteristics
R
L
= 35
144mA
TIME (2.5ms/div.)
I
OUT
(100mA/div
.
)
V
EN
(5V/div
.
)
V
FLG
(5V/div
.
)
V
OUT
(2V/div
.
)
C
L
= 10
F
Turn-On, Turnoff
Characteristics
R
L
= 35
C
L
= 150
F
TIME (2.5ms/div.)
I
OUT
(100mA/div
.
)
V
EN
(5V/div
.
)
V
FLG
(5V/div
.
)
V
OUT
(2V/div
.
)
144mA
MIC2525
Micrel
MIC2525
6
January 2000
Short Circuit Transient Response
(Short Applied to Output)
1A Current Limit
TIME (500
s/div.)
I
OUT
(1A/div
.
)
V
OUT
(5V/div
.
)
V
FLG
(5V/div
.
)
2.76A
Test Circuit
MIC2525
Ferrite
Bead
EN
OUT
FLG
IN
GND
OUT
NC
NC
I
LOAD
(for Current
Limit Response)
C
L
R
L
5V
10k
I
OUT
0.1F
Functional Characteristics Test Circuit
Current-Limit Response
(Ramped Load)
TIME (1ms/div.)
I
OUT
(1A/div
.
)
V
FLG
(5V/div
.
)
V
OUT
(2V/div
.
)
Current Limit
Threshold
1A Current
Limit
January 2000
7
MIC2525
MIC2525
Micrel
Block Diagram
1.2V
REFERENCE
THERMAL
SHUTDOWN
OSC.
CHARGE
PUMP
OUT
UVLO
GATE
CONTROL
IN
FLG
EN
CURRENT
LIMIT
GND
MIC2525
Micrel
MIC2525
8
January 2000
Functional Description
The MIC2525-1 and MIC2525-2 are high-side switches with
active-high and active-low enable inputs, respectively. Fault
conditions turn off or inhibit turn-on of the output transistor,
depending upon the type of fault, and activate the open-drain
error flag transistor making it sink current to ground.
Input and Output
IN (input) is the power supply connection to the logic circuitry
and the drain of the output MOSFET. OUT (output) is the
source of the output MOSFET. In a typical circuit, current
flows through the switch from IN to OUT toward the load. If
V
OUT
is greater than V
IN
when the switch is enabled, 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 (V
OUT
> V
IN
) when the output is off. In
this situation, the MIC2525 avoids undesirable current flow
from OUT to IN. If V
IN
< 2.5V, UVLO disables the switch.
Thermal Shutdown
Thermal shutdown shuts off the output MOSFET and signals
the fault flag 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 the switch is enabled.
Current Limit Induced Thermal Shutdown
Internal circuitry increases the output MOSFET on-resis-
tance until the series combination of the MOSFET on-resis-
tance and the load impedance limit current to typically 750mA.
The increase in power dissipation, in most cases, will cause
the MIC2525 to go into thermal shutdown. When this is
undesirable, thermal shutdown 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 hundred
milliseconds. The USB controller must therefore recognize a
fault and disable the switch within this time. If the fault is not
removed or the switch is not disabled within this time, then the
device will enter into a thermal oscillation of about 2Hz. This
does not cause any damage to the device. Refer to "Func-
tional Characteristics: Thermal Shutdown Response."
Undervoltage Lockout
UVLO (undervoltage lockout) prevents the output MOSFET
from turning on until V
IN
exceeds approximately 2.5V. In the
undervoltage state, the FLAG will be low. After the switch
turns on, if the voltage drops below approximately 2.3V,
UVLO shuts off the output MOSFET and signals fault flag.
Undervoltage detection functions only when the switch is
enabled.
Current Sensing and Limiting
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 0.5A through the output
MOSFET.
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 three scenarios:
Switch Enabled into Short Circuit
If a switch is powered on or enabled into a heavy load or short-
circuit, the switch immediately goes into a constant-current
mode, reducing the output voltage. The fault flag goes low
until the load is reduced. See the "Functional Characteristics:
Short Circuit Response, Enabled into Short Circuit" photo.
Short Circuit Applied to Output
When a heavy load is applied, a large transient current may
flow until the current limit circuitry responds. Once this
occurs, the device limits current to less than the short-circuit
current limit specification. See the "Short Circuit Transient
Response, Short Applied to Output" graph.
Current-Limit Response
The MIC2525 current-limit profile exhibits a small foldback
effect of approximately 500mA. Once this current-limit thresh-
old 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 MIC2525 will deliver load current up to the
current-limit threshold which is typically 1.6A. Refer to "Func-
tional Characteristics: Current-Limit Response" photo for
details.
Fault Flag
FLG is an N-channel, open-drain MOSFET output. The fault-
flag is active (low) for one or more of the following conditions:
undervoltage (while 2V < V
IN
< 2.7), current limit, or thermal
shutdown. The flag output MOSFET is capable of sinking a
10mA load to typically 100mV above ground.
January 2000
9
MIC2525
MIC2525
Micrel
Applications Information
Supply Filtering
A 0.1
F to 1
F bypass capacitor from IN to GND, located at
the device, is strongly recommended to control supply tran-
sients. Without a bypass capacitor, an output short may
cause sufficient ringing on the input (from supply lead induc-
tance) to damage internal control circuitry.
Input or output transients must not exceed the absolute
maximum supply voltage (V
IN max
= 6V) even for a short
duration.
MIC2525
EN
OUT
FLG
GND
OUT
NC
NC
IN
1
8
2
7
3
6
4
5
0.1F to 1F
3V to 5.5V
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 MIC2525 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 for bus-powered applications as shown in
Figure 2.
The soft start circuit shown in Figure 3 can be utilized to meet
USB transient regulation specifications with large load ca-
pacitances (C
BULK
> 10uF). The MIC2525 will provide inrush
current limiting for these applications.
Transient Overcurrent Filter
When the MIC2525 is enabled, large values of capacitance
at the output of the device will cause inrush current to exceed
the short circuit current-limit threshold of the device and
assert the flag. The duration of this time will depend on the
size of the output capacitance. Refer to the "Functional
Characteristics" turn-on and turnoff behaviors for details.
MIC2525-xBM
EN
OUT
FLG
GND
OUT
NC
IN
1
8
2
7
3
6
5
0.1F
Capacitive
Load
USB
Controller
NC
4
Bus Powered Hub
Downstream USB Device
Cable
Cable
USB Host
V
BUS
GND
4.7
F
C
BULK
Figure 2. Soft-Start Application
MIC2525-2
EN
OUT
FLG
GND
OUT
NC
IN
1
8
2
7
3
6
5
USB
Controller
NC
4
USB Peripheral
Cable
USB Hub
C
BULK
GND
V
BUS
4.7
F
USB
Function
Figure 3. Inrush Current-Limit Application
MIC2525
Micrel
MIC2525
10
January 2000
During the capacitance charging time, the device enters into
constant-current mode. As the capacitance is charged, the
current decreases below the short circuit current-limit thresh-
old, and the flag will then be deasserted.
In USB applications, it is required that output bulk capaci-
tance is utilized to support hot-plug events. When the MIC2525
is enabled, the flag may go active for about 1ms due to inrush
current exceeding the current-limit setpoint. Additionally,
during hot-plug events, inrush currents may also cause the
flag to go active for 30
s. Since these conditions are not valid
overcurrent faults, the USB controller must ignore the flag
during these events. To prevent this erroneous overcurrent
reporting, a 1ms RC filter as shown in Figure 4 may be used.
Alternatively, a 1ms debounce routine may be programmed
into the USB logic controller, eliminating the need for the RC
filter.
10k
10k
V+
0.1
F
MIC2525
EN
OUT
FLG
GND
OUT
NC
NC
IN
1
8
2
7
3
6
4
5
OVERCURRENT
USB Controller
Figure 4. Transient Filter
January 2000
11
MIC2525
MIC2525
Micrel
Package Information
45
0
8
0.244 (6.20)
0.228 (5.79)
0.197 (5.0)
0.189 (4.8)
SEATING
PLANE
0.026 (0.65)
MAX
)
0.010 (0.25)
0.007 (0.18)
0.064 (1.63)
0.045 (1.14)
0.0098 (0.249)
0.0040 (0.102)
0.020 (0.51)
0.013 (0.33)
0.157 (3.99)
0.150 (3.81)
0.050 (1.27)
TYP
PIN 1
DIMENSIONS:
INCHES (MM)
0.050 (1.27)
0.016 (0.40)
8-Pin SOP (M)
0.380 (9.65)
0.370 (9.40)
0.135 (3.43)
0.125 (3.18)
PIN 1
DIMENSIONS:
INCH (MM)
0.018 (0.57)
0.100 (2.54)
0.013 (0.330)
0.010 (0.254)
0.300 (7.62)
0.255 (6.48)
0.245 (6.22)
0.380 (9.65)
0.320 (8.13)
0.0375 (0.952)
0.130 (3.30)
8-Pin Plastic DIP (N)
MIC2525
Micrel
MIC2525
12
January 2000
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
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.
2000 Micrel Incorporated
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