RT9715 データシートの表示（PDF） - Richtek Technology

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RT9715

90mΩ, 2A/1.5A/1.1A/0.7A High-Side Power Switches with Flag

Richtek Technology 

RT9715

turns the pass element off. The pass element turn on again

after the junction temperature cools to 80°C. The RT9715

lowers its OTP trip level from 120°C to 100°C when output

short circuit occurs (VOUT < 1V) as shown in Figure 1.

VOUT Short to GND

1V

VOUT

IOUT

Thermal

Shutdown

OTP

Trip

120 °C

Point

100 °C

100 °C

IC Temperature

80 °C

Figure 1. Short Circuit Thermal Folded Back Protection

when Output Short Circuit Occurs (Patent)

Power Dissipation

The junction temperature of the RT9715 series depend on

several factors such as the load, PCB layout, ambient

temperature and package type. The output pin of the

RT9715 can deliver the current of up to 2A (RT9715A/B),

1.5A (RT9715C/D), 1.1A (RT9715E/F) and 0.7A (RT9715G/

H) respectively over the full operating junction temperature

range. However, the maximum output current must be

derated 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 current

and the RDS(ON) of the switch as below.

PD = RDS(ON) x IOUT2

Although the devices are rated for 2A, 1.5A, 1.1A and 0.7A

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 any set of conditions can be estimated by

the following thermal equation :

PD (MAX) = ( TJ (MAX) - TA ) / θJA

Where TJ (MAX) is the maximum junction temperature of

the die (100°C) and TA is the maximum ambient temperature.

DS9715-03 April 2011

The junction to ambient thermal resistance (θJA) for

SOT-23-5/TSOT-23-5, SOP-8/MSOP-8 and WDFM-8L 3x3

packages at recommended minimum footprint are 250°C/

W, 160°C/W and 108°C/W respectively (θJA is layout

dependent).

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.

Over-Current protection devices such as fuses and PTC

resistors (also called polyfuse or polyswitch) have slow

trip times, high on-resistance, and lack the necessary

circuitry for USB-required fault reporting.

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