ISL6118 View Datasheet(PDF) - Renesas Electronics
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ISL6118 Datasheet PDF : 10 Pages
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ISL6118
Introduction
The ISL6118 is a fully independent dual channel overcurrent
(OC) fault protection IC for the +2.5V to +5.5V environment.
Each ISL6118 incorporates in a single 8-lead SOIC package two
80mW N-channel MOSFET power switches for power control.
See Figure 2 for integrated FET on resistance curves.
Independent enabling inputs and fault reporting outputs
compatible with 3V and 5V logic allow 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.
Key Feature Description and Operation
UV Lockout
The ISL6118 undervoltage (UVLO) lockout 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 and eliminates bus voltage
drooping caused by inrush 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 external
EMI filters necessary on other IC products. See Figure 3 for
soft start waveforms.
Fault Blanking on Start-Up
During initial turn-on the ISL6118 prevents nuisance faults from
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 vendors’ products.
Current Regulation
The ISL6118 has integrated current sensing on the power
MOSFETs that allows for rapid control of OC events. Once an
OC condition is detected the ISL6118 goes into its current
regulation (CR) control mode. The ISL6118 CR level is set to a
nominal 0.6A and is regulated to within ±25% over full
temperature, bias voltage range and OC magnitude. The
speed of this control is proportional to the level of OC. Thus a
hard OC is more quickly controlled than a marginal condition.
See Figures 4 through 7 for current regulation performance
curves and waveforms.
Latch-Off Time Delay
The primary function of any OC protection device is to quickly
isolate the voltage bus from a faulty load. Unlike other
manufacturers’ IC products that sense the IC thermal condition
to isolate a faulty load, the ISL6118 uses an internal 12ms
timer that starts upon OC detection. Once an OC condition is
detected, the appropriate output is current limited for 12ms to
allow transient conditions to pass before latch-off. The time to
latch-off is independent of the device’s thermal or adjacent
FN9008 Rev 2.00
March 2004
switch’s electrical condition. See Figure 10 for waveforms
illustrating independent latch-off.
If, after the ISL6118 has latched off, and the fault has asserted
and the enable is not deasserted but the OC condition still
exists, the ISL6118 (unlike other IC devices) does not send to
the controller a continuous string of fault pulses. The ISL6118’s
single fault signal is sent at the time of latch off.
Slow and Fast Shutdown
The ISL6118 has two shutdown modes. When disabled with a
load current less than the current regulation (CR) level the
ISL6118 shuts down in a controlled manner using a 500nA
constant current source controlled ramp. When disabled during
CR or if the timer has expired the ISL6118 quickly pulls down
the output thereby quickly removing the faulted load from the
voltage bus. See Figures 8 and 9 for illustrative waveforms of
each shutdown mode.
Over Temperature Shutdown
Although the ISL6118 has a thermal shutdown feature,
because of the 12ms timed shutdown this will only be invoked
in extremely high ambient temperatures.
Active Output Pulldown
Another unique ISL6118 feature is the active pull down on the
outputs to 300mV above GND when the device is disabled.
Figure 1 illustrates the ISL6118 operational waveforms,
showing the relationships between the various I/O signals
during typical and faulted conditions. It also graphically
highlights many of the terms and modes of operation referred
to in this data sheet.
Using the ISL6118EVAL1 Platform
General and Biasing Information
The ISL6118EVAL1 platform, Figure 14, allows evaluation of
the ISL6118 dual power supply control IC and comparison
against a suitably sized PPTC component.
The evaluation platform is biased and monitored through
numerous test points (TP#). See Table 1 for test point
assignments and descriptions.
TABLE 1. ISL6118EVAL1 TEST POINT ASSIGNMENTS
TP #
DESCRIPTION
TP1
Eval Board and IC GND
TP2
Eval Board +3.3V Bias
TP3
Enable Switch 1
TP4
Enable Switch 2
TP5
Switch 2 Fault
TP6
Switch Out 2
TP7
Switch Out 1
TP8
Switch 1 Fault
TP9
IC VIN Pin
TP10
PPTC Load Side
TP11
Invoke Overcurrent
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