ISL6119 データシートの表示（PDF） - Renesas Electronics

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ISL6119

USB Dual Port Power Supply Controller

Renesas Electronics 

ISL6119

Introduction

The ISL6119 is a fully independent dual channel overcurrent

(OC) fault protection IC for the +2.5V to +5.5V environment.

Each ISL6119 incorporates in a single 8 lead SOIC package

two 80mW N-channel MOSFET power switches for power

control. Independent enabling inputs and fault reporting

outputs compatible with 3V and 5V logic allows for external

control and monitoring. This device features internal current

monitoring, accurate current limiting, integrated power

switches and current limited timed delay to latch-off for system

protection. See Figure 1 for typical operational waveforms

including both under and overcurrent situations.

Key Feature Description and Operation

UV Lock Out

The ISL6119 undervoltage lockout feature prevents

functionality of the device unless the correct ENABLE state

and VIN > 2.5V are present.

Soft Start

A constant 500nA current source ramps up the switch’s gate

causing a voltage follower effect on the output voltage. This

provides a soft start turn-on eliminating bus voltage drooping

caused by in-rush current charging heavy load capacitances.

Rising and falling outputs are current limited voltage ramps so

that both the inrush current and voltage slew rate are limited,

independent of load. This reduces supply droop due to surge

and also eliminates the need for EMI filters necessary on other

IC products.

Fault Blanking On Start-Up

During initial turn-on the ISL6119 prevents nuisance faults

being reported to the system controller by blanking the fault

signal for 12ms. This blanking eliminates the need for external

RC filters necessary for other vendor products that assert a

fault signal upon initial turn-on into a temporary high current

condition. See Figures 10 through 12 for waveform examples.

Current Regulation

The ISL6119 has integrated current sensing on the power

MOSFET that allows for rapid control of OC events. Once an

OC is detected the ISL6119 goes into its current regulation

(CR) control mode. The ISL6119 CR level is set to a nominal

1A. This current regulation is 25% over the full operating

temperature and voltage bias range. See Figures 4 and 5 for

illustrative curves. The speed of this control is inversely related

to the magnitude of the OC fault. Thus a hard overcurrent is

more quickly controlled than a marginal OC condition. See

Figure 6 for waveforms illustrating this and Figure 7 for an

accompanying graph.

Over Temperature Shutdown

Although the ISL6119 has a thermal shutdown feature,

because of the 12ms timed shutdown this will only be invoked

in extremely high ambient temperatures

Latch-Off Time Delay

The primary function of any OC protection device is to quickly

isolate the voltage bus from a faulty load. Unlike many other IC

products that sense the IC thermal condition (the monitored IC

junction temperature depends on a number of factors the most

important of which are power dissipation of the faulted and

adjacent switches and package temp) to isolate a faulty load,

the ISL6119 uses an internal 12ms timer that starts upon OC

detection. Once an OC condition is detected the appropriate

output is current limited for a maximum of 12ms to allow

transient conditions to pass before latch-off. This time to latch-

off is independent of device thermal or adjacent switch

condition. See Figure 18 for waveforms illustrating

independent latch-off.

If, after the ISL6119 has latched off, and the fault has asserted

and, the enable is not deasserted but the OC condition still

exists, the ISL6119 unlike other IC devices does not send to

the controller a continuous string of fault pulses. The ISL6119’s

single fault signal is sent at the time of latch-off unlike other

devices.

Slow And Fast Shutdown

The ISL6119 has two shutdown modes. When turned off with a

load current less than the current regulation (CR) level the

ISL6119 shuts down in a controlled manner using a 500nA

constant current source controlled ramp. When latched off due

to CR and the timer has expired, the ISL6119 quickly pulls

down the output thereby quickly removing the faulted load from

the voltage bus. See Figures 8 and 9 for waveforms of each

mode.

Active Output Pulldown

Another unique ISL6119 feature is the active pull down on the

outputs to 300mV above GND when the device is disabled.

Competitors’ parts’ switch leakage causes the output voltage to

drift up to VIN voltage even when the part is supposed to be

disabled.

ON OFF

ENABLE

FAULT

VOUT

LATCH-OFF SET

RESET BY

ENABLE

CURRENT

REGULATION

SETTLING TIME

(1.4ms)

OVER CURRENT

IOUT

1A CURRENT

LIMIT

12ms CURRENT REGULATION PERIOD

FIGURE 1. TYPICAL OPERATIONAL WAVEFORMS

FN9002 Rev 3.00

March 2004

Page 5 of 13

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