CM2026
D
UAL
USB P
OWER
C
ONTROL
S
WITCH
GENERAL DESCRIPTION
The CM2026 is a dual integrated high-side power switch with
independent enable and flag functions, optimized for
self-powered and bus-powered Universal Serial Bus (USB)
applications. Few external components are necessary to
satisfy USB requirements.
The CM2026 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 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.
Additional features include thermal shutdown to prevent
catastrophic switch failure from high-current loads,
undervoltage lockout (UVLO) to ensure that the device
remains off unless there is a valid input voltage present, and
3.3V and 5V logic compatible enable inputs.
The CM2026 is available in active-high version in 8-pin DIP
and SOIC packages.
FEATURES
Compliant to USB specifications
UL Recognized Component
2 independent switches
3V to 5.5V input
500mA minimum continuous load current per port
140mΩ maximum on-resistance
1.25A maximum short circuit current limit
Individual open-drain fault flag pins
110uA typical on-state supply current
1uA 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 enable version
8-pin SOIC and DIP packages
APPLICATIONS
USB host and self-powered hubs
USB bus-powered hubs
Hot plug-in power supplies
Battery-charger circuit
PIN CONFIGURATION
PDIP-08/SOP-08
(Top View)
1
2
3
4
EN1
FLG1
FLG2
EN2
OUT1
IN
GND
OUT2
8
7
6
5
2002/05/29
Rev. 2
Champion Microelectronic Corporation
Page 1
CM2026
D
UAL
USB P
OWER
C
ONTROL
S
WITCH
PIN DESCRIPTION
Pin No.
1,4
EN(1/2)
Symbol
1.
2.
2,3
6
7
8,5
FLG(1/2)
GND
IN
OUT(1/2)
Description
V
IN
= 3.3V, Enable (Input): Logic-compatible enable input. High input > 2.1V
typical. Low input < 1.9V typical. Do not float.
V
IN
= 5V, Enable (Input): Logic-compatible enable input. High input > 3.5V
typical. Low input < 3.3V typical. Do not float.
Fault Flag (Output): open-drain output. Indicates overcurrent, UVLO, and thermal
shutdown.
Ground: Supply return.
Supply Input: Output MOSFET drain. Also supplies IC's internal circuitry. Connect
to positive supply.
Switch Output: Output MOSFET source. Typically connect to switched side of
load.
BLOCK DIAGRAM
5V
R3
R2
47K
R1
47K
U1 CM2026
VIN
ON/OFF
1
2
4.5~5V
3
4
3
2
1
4
FLG2
EN2
GND
OUT2
6
5
J2
1
2
3
4
USBPORT1
J3
1
2
3
4
USBPORT1
EN1
FLG1
OUT1
IN
8
7
C1
0.1U
CM1085
3.3V
10K
R4
10K
ON/OFF
usb mcu
3.3 USB CPU
ORDERING INFORMATION
Part Number
CM2026IS
CM2026IP
Enable
Active High
Active High
Temperature Range
-40℃ to +85℃
-40℃ to +85℃
Package
8-Pin SOIC (S08)
8-Pin PDIP (P08)
2002/05/29
Rev. 2
Champion Microelectronic Corporation
Page 2
CM2026
D
UAL
USB P
OWER
C
ONTROL
S
WITCH
ABSOLUTE MAXIMUM RATINGS
(Note 1)
OPERATING RATINGS
(Note 2)
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℃ to +150℃
Lead Temperature (Soldering 5 sec.) ……………… 260℃
ESD Rating,
Note 3
……………………………………. 2kV
Supply Voltage (V
IN
) ………………………… +3V to +5.5V
Ambient Operating Temperature (T
A
) ….. -40℃ to +85℃
Thermal Resistance
SOIC (Θ
JA
) ……………………………………120℃/W
DIP (Θ
JA
) ………………………………………130℃/W
ELECTRICAL CHARACTERISTICS
V
IN
= +5V; T
A
= +25℃; unless noted
Parameter
Supply Current
Test Conditions
Note 4,
switch off, OUT = open
Note 4,
all switches on, OUT = open
Low-to-high transition
Enable Input Threshold
High-to-low transition,
Note4
Enable input Current
Enable Input Capacitance
Switch Resistance
Output Turn-On Delay
Output Turn-On Rise Time
Output Turn-Off Delay
Output Turn-Off Fall Time
Output Leakage Current
Continuous Load Current
Short-Circuit Current Limit
Current-Limit Threshold
Overtemperature Shutdown
Threshold
Error Flag Output Resistance
Error Flag Off Current
UVLO Threshold
V
IN
= 5V, I
OUT
= 500mA, each switch
V
IN
= 3.3V, I
OUT
= 500mA, each switch
R
L
= 10Ω each output
R
L
= 10Ω each output
R
L
= 10Ω each output
R
L
= 10Ω each output
Each output (output disabled0
Each output
Each output (enable into load), V
OUT
=
4.0V
Ramped load applied to enabled output,
V
OUT
≦4.0V,
Note 5
T
J
increasing
T
J
decreasing
V
IN
= 5V, I
L
= 10mA
V
IN
= 3.3V, I
L
= 10mA
V
FLG
= 5V
V
IN
= increasing
V
IN
= decreasing
0.5
0.5
0.75
1.6
135
125
10
15
0.01
2.5
2.3
25
40
1
1.25
2.2
V
EN
= 0V to 5.5V
V
IN
= 3.3V
V
IN
= 5V
V
IN
= 3.3V
V
IN
= 5V
-1
CM2026
Min.
Typ.
0.75
110
2.1
3.5
1.9
3.3
±0.01
1
100
140
0.5
1
1
1
20
20
10
140
180
1
Max.
5
160
Unit
μA
μA
V
V
μA
PF
mΩ
mΩ
ms
ms
μs
μs
μA
A
A
A
℃
℃
Ω
Ω
μA
V
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.
The enable input has approximately 200mV of hysteresis. See control threshold charts.
Note 5.
See "Functional Characteristics: Current-Limit Response" photo.
2002/05/29
Rev. 2
Champion Microelectronic Corporation
Page 3
CM2026
D
UAL
USB P
OWER
C
ONTROL
S
WITCH
FUNCTIONAL DESCRIPTION
The CM2026 is dual high-side switch with active-high 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
IN (input) is the power supply connection to the logic circuitry
and the drain of the output MOSFET. OUTx (output) is the
source of its respective 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 a switch is enabled, current will
flow from OUT to IN since the MOSFET is bi-directional 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 drain (V
OUT
> V
IN
) when the output is off. In this
situation, the CM2026 avoids undesirable current flow from
OUT to IN. If V
IN
< 2.5V, UVLO disables both switches.
Thermal Shutdown
Thermal shutdown shuts off the affected output MOSFETs
and signals all fault flags if the die temperature exceeds 135
℃.
10℃ of hysteresis prevents the switch from turning on
until the die temperature drops to 125℃. 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 limit current to typically 850mA. The
increase in power dissipation, in most cases, will cause the
CM2026 to go into thermal shutdown, disabling affected
channels. 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 appropriate
channel with this time. If the fault is not removed or the switch
is not disabled with the time, then the device will enter into a
thermal oscillation of about 2Hz. This does not cause any
damage to the device. Refer to "Functional 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 at least one
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
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 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.
Short Circuit Applied to Output
When a heavy load is applied, a large transient current may
flow until the current limit circuitry will respond. Once this
occurs, the device limits current to less than the short-circuit
current limit specification.
Current-Limit Response
The CM2026 current-limit profile exhibits a small foldback
effect of approximately 500mA. Once this current-limit
threshold is exceeded the device enters constant current
mode.
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
<2.7V), current limit, or thermal
shutdown. The flag output MOSFT is capable of sinking a
10mA load to typically 100mV above ground. Multiple FLG
pins may be "wire NORed" to a common pull-up resistor.
2002/05/29
Rev. 2
Champion Microelectronic Corporation
Page 4
CM2026
D
UAL
USB P
OWER
C
ONTROL
S
WITCH
APPLICATIONS INFORMATION
Supply Filtering
A 0.1μF to 0.1μF 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 (V
IN max
= 6V) even for a short
duration.
Transient Overcurrent Filter
When the CM2026 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. 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
threshold old, and the flag will then be deserted.
In USB applications, it is required that output bulk capacitance
is utilized to support hot-plug events. When the CM2026 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 30uS. 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
programmed into the USB logic controller, eliminating the
need for the RC filter.
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 CM2026 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
capacitances (C
BULK
> 10uF). The CM2026 will provide inrush
current limiting for these applications.
2002/05/29
Rev. 2
Champion Microelectronic Corporation
Page 5
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