ISL6186_14 Datasheet, PDF (8/18 Pages) Intersil Corporation – USB Port Power Supply Controller

ISL6186
Functional Description
Power On Reset (POR)
The ISL6186 POR feature inhibits device functionality when V_IN
<V_UVLO.
Reverse Polarity Protection
In any event in which the power switch is disabled or powered
down, and V_OUT > V_IN, there will be no output to input current
flow, nor will the output voltage appear on the input.
Soft-Start
Upon enable, the voltage on the VOUT pin will ramp up according
to the equation: I_LIM/C_OUT (V/s). Resistive or active load will slow
the V_OUT ramp-up toward the top of its curve.
Fault Blanking On Start-Up
During initial turn-on, the ISL6186 prevents nuisance faults being
reported to the system controller by blanking the fault signal until
the internal FET is fully enhanced.
Current Trip and Limiting Levels
The ISL6186 provides integrated current sensing in the MOSFET,
which allows for rapid control of OC events. Once an OC condition
is detected, the ISL6186 goes into its current limiting (CL) control
mode. The ISL6186 is variant specified to allow a continuous
current (I_CONT) operation of 1.5A, 3A or 3.6A. As the current
increases past its continuous current rating, it will reach a level
that causes the device to enter its current limit mode; that is, the
current trip level. The current trip level is in all cases adequately
above the I_CONT rating so as not to cause unintended false faults.
The current limit is specified at V_OUT = V_IN - 1V to test a known
representative condition and is featured at a nominal value
slightly higher than the continuous current rating. The speed of
this current limiting control is inversely related to the magnitude
of the OC fault. Thus, a hard overcurrent is more quickly pulled to
its limiting value than a marginal OC condition.
Typical Performance Curves
85
80
75
70
V_IN = 2.5V
65
60
V_IN = 3.3V
55
50
45
V_IN = 5V
40
35
-40 -25 0 25 45 75 85 115
TEMPERATURE (°C)
FIGURE 3. SWITCH ON-RESISTANCE AT 0.5A
Over-Temperature Shutdown
Although the ISL6186 has an over-temperature shutdown and
lockout feature because of the 12ms timed shutdown, the
thermal shutdown is likely only to be invoked in extremely high
ambient temperatures. FAULT does not respond to OT events.
The over- temperature protection invokes and disables the switch
turn-on operation. Once the die temperature is ~+140°C, it will
turn off an already on switch at ~+150°C and releases the part
to operation once the die temperature falls to ~+120°C.
Turn-off Time Delay
During operation, once an OC condition is detected, the output
is current limited for ~12ms to allow transient OC conditions to
pass. If still in current limit and after the current limit period
has elapsed, the output is then turned off, and the fault is
reported by pulling the FAULT output low. The internal 12ms
timer starts upon current limiting and is independent of ambient
or IC thermal conditions, thus providing more consistent
operation over the entire temperature range.
Latch-off Restart/Auto-Restart Start
After turn-off, with the latch-off options, both the output and the
FAULT signal are latched low until reset by the enable signal
being de-asserted, at which time the FAULT signal will clear and
the IC is ready for enable to assert. On the auto-restart options,
the ISL6186 will attempt to periodically turn on the output at
approximately 1s intervals as long as the enable is asserted. If
the OC condition remains indefinitely, so will the fault indication
and the restart attempts, until such time as the thermal
protection feature is invoked, thus increasing the restart period.
Power-Good Output
This feature is an active low, open-drain, power-good indicator
that asserts after V_OUT/V_IN>90% and de-asserts when V_OUT/V_IN
< 85%. It immediately de-asserts upon the IC being disabled.
Active Output Pull-down
Another ISL6186 feature is the 10kΩ active pull-down on the
outputs to <60mV above GND when the device is disabled, thus
ensuring discharge of the load.
1.3
1.2
1.1
1.0
0.9
0.8
0.7
-40 -25
0 25 45 75
TEMPERATURE (°C)
85 115
FIGURE 4. NORMALIZED SWITCH RESISTANCE
8
FN7698.2
November 3, 2011