ISL6118 Datasheet, PDF (7/10 Pages) Intersil Corporation – Dual Power Supply Controller

ISL6118
Typical Performance Curves (Continued)
ISL6118
V_OUT
3.29V (0.075Ω)
V_VIN
3.32V
0.4A HOLD
CURRENT PPTC
2.93V (1.1Ω)
VIN
0.4A HOLD CURRENT PPTC OUT
GND
VOLTAGE (0.5V/DIV)
FIGURE 11. ISL6118 vs PPTC INTO 8.2Ω LOAD
ISL6118 CR
12ms PERIOD
ISL6118 OUT
VOLTAGE (0.5V/DIV)
TIME (4ms/DIV)
FIGURE 12. ISL6118 vs PPTC INTO 3.5Ω LOAD
VIN
0.4A HOLD CURRENT PPTC OUT
2.3V AT 10s
1.5V AT 30s
ISL6118 OUT
VOLTAGE (0.5V/DIV)
TIME (4s/DIV)
FIGURE 13. ISL6118 vs PPTC WITH EXTENDED 3.5Ω LOAD
Using the ISL6118EVAL1 Platform
Upon proper bias the PPTC, F1, has a nominal 400mA load
current passing through it which is the hold current rating for
that particular device. Removal of the PPTC is necessary to
isolate the ISL6118 as the PPTC load current is common to
the ISL6118EVAL1 bias connections.
By enabling either or both of the ISL6118H switches by
signaling TP3 and/or TP4 high (>2.4V) these switches are
also loaded with a nominal 400mA current.
Provided test points enable the evaluation of voltage loss
across the PPTC (TP9 - TP10) and likewise across the
ISL6118 enabled switches (TP9 - TP6 and TP7). Expect to
see 100% - 300% greater voltage loss across the PPTC than
the ISL6118 (see Figure 11 for ISL6118 vs PPTC voltage
loss comparison).
An overcurrent (OC) condition can be invoked on both the
ISL6118 and the PPTC by driving TP11 to +6V, causing SW1
to close and a nominal 0.94mA load is imposed. This
represents a current overload to the ISL6118 and is thus
quickly current regulated to the 600mA limit. If the OC
duration extends beyond the nominal 12ms of the internal
ISL6118 timer then the output is latched off and the fault
output is asserted by being pulled low turning on the
appropriate FAULT LED. (Please note: the labeling for the
FAULT-1 and FAULT-2 is reversed.) The eval board is
designed to only invoke a OC condition on channel 2 (TP4)
so that a channel to channel isolation evaluation in the
presence of a OC condition can be evaluated.
The primary function of any OC protection device is to
quickly isolate the voltage bus from a faulty load. Unlike the
PPTC and other vendor available IC products, the ISL6118
internal timer that starts upon OC detection provides
consistent protection that is independent of temperature.
Figures 11 through 13 illustrate the comparative efficiency
and effectiveness of the ISL6118 vs the PPTC in protecting
and isolating a faulty load capable from drooping the system
bus in that system.
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