AP2151SG-13 Diodes Zetex, AP2151SG-13 Datasheet - Page 12

• Manufacturer Part Number: AP2151SG-13
• Manufacturer: Diodes Zetex

Specifications of AP2151SG-13

• Usb Power Switch Type: High Side Switch
• Short Circuit Current Limit: 800mA
• Input Voltage Range: 2.7 to 5.5V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 8
• Package Type: SOP
• Lead Free Status / RoHS Status: Compliant

Application Note
Power Dissipation and Junction Temperature
The low on-resistance of the internal MOSFET allows the small surface-mount packages to pass large
current. Using the maximum operating ambient temperature (T
calculated by:
Finally, calculate the junction temperature:
Where:
Thermal Protection
Thermal protection prevents the IC from damage when heavy-overload or short-circuit faults are present for
extended periods of time. The AP2141/AP2151 implements a thermal sensing to monitor the operating
junction temperature of the power distribution switch. Once the die temperature rises to approximately 140°C
due to excessive power dissipation in an over-current or short-circuit condition the internal thermal sense
circuitry turns the power switch off, thus preventing the power switch from damage. Hysteresis is built into
the thermal sense circuit allowing the device to cool down approximately 25°C before the switch turns back
on. The switch continues to cycle in this manner until the load fault or input power is removed. The
FLG open-drain output is asserted when an over-temperature shutdown or over-current occurs with 7-ms
deglitch.
Under-voltage Lockout (UVLO)
Under-voltage lockout function (UVLO) keeps the internal power switch from being turned on until the power
supply has reached at least 1.9V, even if the switch is enabled. Whenever the input voltage falls below
approximately 1.9V, the power switch is quickly turned off. This facilitates the design of hot-insertion systems
where it is not possible to turn off the power switch before input power is removed.
Host/Self-Powered HUBs
Hosts and self-powered hubs (SPH) have a local power supply that powers the embedded functions and the
downstream ports (see Figure 2). This power supply must provide from 5.25V to 4.75V to the board side of
the downstream connection under both full-load and no-load conditions. Hosts and SPHs are required to
have current-limit protection and must report over-current conditions to the USB controller. Typical SPHs are
desktop PCs, monitors, printers, and stand-alone hubs.
AP2141/AP2151 Rev. 6
DS31562
P
T
T
R
P
J
A
D
D
θJA
= Ambient temperature °C
= P
= R
= Total power dissipation
= Thermal resistance
D
DS(ON)
x R
θJA
× I
+ T
2
A
Figure 2. Typical One-Port USB Host / Self-Powered Hub
(Continued)
0.5A SINGLE CHANNEL CURRENT-LIMITED POWER
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A
) and R
DS(ON)
AP2141/AP2151
, the power dissipation can be
©
Diodes Incorporated
JUNE 2009
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