ap2196 Diodes, Inc., ap2196 Datasheet - Page 14

• Manufacturer Part Number: ap2196
• Description: 1.5a Dual Channel Current-limited Power Switch
• Manufacturer: Diodes, Inc.

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 (TA) and RDS(ON), the power dissipation can
be 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 AP2186/AP2196 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.
AP2186/AP2196 Rev 1
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
Controller
× I
+ T
USB
2
A
Figure 2. Typical Two-Port USB Host / Self-Powered Hub
(Continued)
Power Supply
3.3V
5V
0.1uF
8
3
5
4
2
www.diodes.com
1.5A DUAL CHANNEL CURRENT-LIMITED POWER
FLG1
EN1
FLG2
EN2
IN
14 of 17
AP2186
GND
1
OUT1
OUT2
7
6
0.1uF
0.1uF
AP2186/AP2196
68uF
68uF
Downstream
USB Ports
D+
D-
GND
V
GND
D+
D-
V
BUS
BUS
©
Diodes Incorporated
APRIL 2009
SWITCH