RT9715CA

9

DS9715CA-00 April 2015

www.richtek.com

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Copyright 2015 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

Power Dissipation

The junction temperature of the RT9715CA series depend

on several factors such as the load, PCB layout, ambient

temperature and package type. The output pin of the

RT9715CA can deliver the current of up to 1.5A

(RT9715CA) over the full operating junction temperature

range. However, the maximum output current must be

decreased at higher ambient temperature to ensure the

junction temperature does not exceed 100

°C. With all

possible conditions, the junction temperature must be

within the range specified under operating conditions.

Power dissipation can be calculated based on the output

Although the device is rated for 1.5A of output current,

but the application may limit the amount of output current

based on the total power dissipation and the ambient

temperature. The final operating junction temperature for

Thermal Shutdown

Thermal protection limits the power dissipation in

RT9715CA. When the operation junction temperature

exceeds 120

°C, the OTP circuit starts the thermal

shutdown function and turns the pass element off. The

pass element turn on again after the junction temperature

cools to 80

°C. The RT9715CA lowers its OTP trip level

from 120

°C to 100°C when output short circuit occurs

any set of conditions can be estimated by the following

thermal equation :

the die (100

The junction to ambient thermal resistance (

SOT-23-5 package at recommended minimum footprint

are 250

Universal Serial Bus (USB) & Power Distribution

The goal of USB is to enable device from different vendors

to interoperate in an open architecture. USB features

include ease of use for the end user, a wide range of

workloads and applications, robustness, synergy with the

PC industry, and low-cost implementation. Benefits

include self-identifying peripherals, dynamically attachable

and reconfigurable peripherals, multiple connections

(support for concurrent operation of many devices), support

for as many as 127 physical devices, and compatibility

with PC Plug-and-Play architecture.

The Universal Serial Bus connects USB devices with a

USB host: each USB system has one USB host. USB

devices are classified either as hubs, which provide

additional attachment points to the USB, or as functions,

which provide capabilities to the system (for example, a

digital joystick). Hub devices are then classified as either

Bus-Power Hubs or Self-Powered Hubs.

A Bus-Powered Hub draws all of the power to any internal

functions and downstream ports from the USB connector

power pins. The hub may draw up to 500mA from the

upstream device. External ports in a Bus-Powered Hub

can supply up to 100mA per port, with a maximum of four

external ports.

Self-Powered Hub power for the internal functions and

downstream ports does not come from the USB, although

the USB interface may draw up to 100mA from its

upstream connect, to allow the interface to function when

the remainder of the hub is powered down. The hub must

be able to supply up to 500mA on all of its external

downstream ports. Please refer to Universal Serial

Specification Revision 2.0 for more details on designing

compliant USB hub and host systems.

Figure 1. Short Circuit Thermal Folded Back Protection

when Output Short Circuit Occurs (Patent)

1V

Thermal

Shutdown

OTP Trip Point

120 C



100 C



100 C



80 C



IC Temperature