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Электронный компонент: GM2526L-S8

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GM2526
DUAL USB POWER SWITCH
Revision 2, February 2003 www.gammamicro.com
PRELIMINARY
The GM2526 is a dual high-side integrated power switch with independent enable and flag functions, designed for
self- and bus-powered Universal Serial Bus (USB) applications. The GM2526 requires few external components.
Each of the two switch channels supplies up to 500mA as required by USB downstream devices. Each switch's
low on-resistance meets USB voltage drop requirements. Fault current is 750mA (typical), well below the UL
25VA safety requirements. A flag output indicates fault conditions to the local USB controller. The soft-start
feature prevents the transient voltage drop on the upstream port that can occur when the switch is enabled in bus-
powered applications. Thermal shutdown protection prevents switch failure from high-current loads. Undervoltage
lockout (UVLO) hold the GM2526 off unless there is a correct input voltage. The GM2526 has 3.3V and 5V logic
-compatible Enable inputs.
The GM2526 is available in Active-High and Active-Low versions and comes in 8-pin DIP and SOIC packages.
PIN CONFIGURATION
1
1
2
3
4
5
6
7
8 OUTA
IN
OUTB
ENA
FLGA
FLGB
ENB
GND
Compliant to USB Specifications
Two Independent Switches
Input from 3V to 5.5V
Min. Continuous Load Current 500mA per port
Max. ON-Resistance 140m
Max. Short Circuit Current Limit 1.25A
Individual Open-Drain Fault Flag Pins
ON-State Supply Current 110


A (typ.)
OFF-State Supply Current 1


A (typ.)
Thermal Shutdown
Undervoltage Lockout (UVLO) Typically 2.4V
1ms Turn-ON (soft-start) and Fast Turn-OFF
Active-High or Active-Low Enable Versions
GM2526-x
8-pin SOIC
8-pin DIP
(Top View)
Applications:
USB Power Management
USB Host- and Self-Powered Hubs
USB Bus-Powered Hubs
Hot Plug-In Power Supplies
Battery-Charger Circuits
1
2
3
4
6
OUTA
IN
OUTB
ENA
FLGA
FLGB
ENB
GND
7
5
8
LOGIC,
CHARGE
PUMP
LOGIC,
CHARGE
PUMP
CONNECTION DIAGRAM
GM2526
DUAL USB POWER SWITCH
Revision 2, February 2003 www.gammamicro.com
PRELIMINARY
2
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RECOMMENDED OPERATING CONDITIONS *
* Exceeding the absolute maximum rating may damage the device and will adversely affect reliability. Always operate the GM2526
within "Recommended Operating Conditions" (below).
** Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
* The GM2526 is not guaranteed to function outside these operating ranges.
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PIN DESCRIPTION
GM2526
DUAL USB POWER SWITCH
Revision 2, February 2003 www.gammamicro.com
PRELIMINARY
3
ABSOLUTE MAXIMUM RATINGS
V
IN
= 5V, T
A
= 25C (unless otherwise noted)
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2
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I
,
V
3
.
3
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d
=
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3
.
2
-
V
* OFF is


0.8V, and ON is


2.4V for the GM2526-H. OFF is


2.4V, and ON is


0.8V for the GM2526-L.
The ENABLE input has approximately 200mV of hysteresis.
GM2526
DUAL USB POWER SWITCH
Revision 2, February 2003 www.gammamicro.com
PRELIMINARY
4
GM2526
OUTA
IN
OUTB
ENA
FLGA
FLGB
ENB
GND
Current
Limit
Current
Limit
1.2V Reference
Gate
Control
Gate
Control
UVLO
OSC.
Thermal
Shutdown
Charge
Pump
Charge
Pump
BLOCK DIAGRAM
FUNCTIONAL CHARACTERISTICS TEST CIRCUIT
OUTA
IN
I
OUT
I
LOAD
C
L
R
L
OUTB
ENA
FLGA
FLGB
ENB
GND
Ferrite
Bead
(for Current
Limit Response)
(1 output shown)
5V
10k
0.1
F
GM2526
+
GM2526
DUAL USB POWER SWITCH
Revision 2, February 2003 www.gammamicro.com
PRELIMINARY
5
FUNCTIONAL DESCRIPTION
The GM2526-H (active-high) and GM2526-L (active-low)
are dual high-side switches with. 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, sinking
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 application, 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 bidirectional when active. 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 GM2526 avoids
undesirable current flow from OUT to IN. If V
IN
falls
below 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
C. Hysteresis of 10
C pre-
vents the switch from turning on until the die temperature
drops to 125
C. Note: over-temperature detection
functions only when at least one switch is enabled.
Current Limit Induced Thermal Shutdown
The GM2526 raises the output MOSFET on-resistance
until the series combination of the MOSFET on-
resistance and the load impedance limit current to
850mA (typ.). Normally the increased power dissipation
will activate thermal shutdown, disabling affected
channels of the GM2526. If you prefer to avoid this, you
can respond to the fault and disable the current limited
channel externally before the GM2526 reaches
shutdown temperature. The time between the flag
indicating a current limit fault and thermal shutdown
depends on ambient temperature, board layout, and
load impedance, but you will have typically a few hundred
milliseconds. If you do not want the GM2526 to go into
thermal shutdown, the USB controller recognize a fault
and disable the appropriate channel within this time. If
the fault is not removed or the switch is not disabled
within this time, then the GM2526 will experience
thermal oscillation of about 2Hz. This does not damage
the GM2526.
Undervoltage Lockout
UVLO prevents the output MOSFET from turning on
until V
IN
exceeds approximately 2.5V. Until turn-on, the
FLAG will be low. After the switch turns on, if the voltage
drops below approximately 2.3V, UVLO signals the
fault flag and shuts off the output MOSFET. 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 each channel's output MOSFET.
The current-limit circuit senses a portion of the output
MOSFET 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
according to the circumstances:
a) 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.
b) When a heavy load is applied, a large transient current
may flow until the current limit circuitry responds, at
which point the device limits current to less than the
short-circuit current limit specification.
c) The GM2526 current-limit profile exhibits a small
(~500mA) foldback effect. Once past the current-limit
threshold, the GM2526 operates in constant-current
mode (see "short circuit current limit" in the Electrical
Characteristics).
Note, the GM2526 will deliver load current up to the
current-limit threshold, typically 1.6A.
Fault Flag
FLG is an N-channel, open-drain MOSFET output. The
faultflag is active (low) for one or more of the following
conditions:
undervoltage (2V < V
IN
< 2.7), current limit,
or thermal shutdown. The flag output MOSFET can
sink a 10mA load to 100mV (typically) above ground.
You can "wire NOR" multiple FLG pins to a common
pull-up resistor.