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 bus-
poweredUniversalSerialBus(USB)applications. Fewexter-
nal components are necessary to satisfy USB requirements.
• 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
TheMIC2537satisfiesthefollowingUSBrequirements: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 require-
ments; and a flag output is available to indicate fault condi-
tions to the local USB controller. Soft start eliminates the
momentaryvoltagedropontheupstreamportthatmayoccur
when the switch is enabled in bus-powered applications.
• –40°C to 85°C operation
Additional features include thermal shutdown to prevent
catastrophic switch failure from high-current loads and 3.3V
and 5V logic compatible enable inputs.
Applications
• USB keyboards
The MIC2537 is available in active-high and active-low ver-
sions in a 16-lead SOP package.
• 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
VBUS
10k
10k 10k 10k
Downstream
MIC5207-3.3
D+
D–
33µF*
USB
3.3V USB Controller
LDO Regulator
MIC2537
0.01µF
0.01µF
0.01µF
0.01µF
Port 1
100mA max.
IN
V+
EN
OC
EN
OC
EN
IN
OUT
ENA
GND
1µF
FLGA
ENB
NC
4.7
µF
GND
0.1
µF
OUTA
VBUS
D+
FLGB
ENC
OUTB
OUTC
Downstream
USB
Port 2
100mA max.
33µF*
33µF*
33µF*
D+
D–
FLGC OUTD
OC
EN
OC
D–
GND
END
NC
FLGD
GND
Bold lines indicate
0.1" wide, 1-oz. copper
high-current traces.
GND
VBUS
D+
Downstream
USB
Port 3
100mA max.
D–
* 33µF, 16V tantalum or 100µF, 10V electrolytic per port
GND
VBUS
D+
Downstream
USB
D–
Port 4
100mA max.
GND
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