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ISL6118HIB Folha de dados(PDF) 4 Page - Intersil Corporation |
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ISL6118HIB Folha de dados(HTML) 4 Page - Intersil Corporation |
4 / 10 page 4 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 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 ISL6118 |
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