[introduction] reliable voltage monitor the trade demand that IC is industrial group from beginning to end, because it can raise systematic dependability, change in voltage twinkling and the system promotes property when power source breakdown. Semiconductor manufacturer also is raising voltage monitor ceaselessly the function of IC.
Monitor IC need calls electrify restoration (VPOR) lowermost voltage a future life becomes clear or reliable restoration signal, and before voltage of this lowest power source comes, the condition of restoration signal is not affirmatory. Generally speaking, we are what its say restoration burr. The develop that restoration brings a foot to basically two kinds differ attacks structure, open leakage and push-pull namely (graph 1) , two kinds of develop attack the structure uses NMOS to regard next pulling as MOSFET.
Graph 1. The configuration opening leakage that restoration develop attacks and push-pull are configured
Graph 2. Resetting voltage how with on pull voltage (VPULLUP) rise into scale, bring about the restoration burr that says normally thereby
During electrify, if power source voltage is low at VPOR, do not have enough voltage can drive interior MOSFET works, because this MOSFET is shut. Right now, monitor cannot undertake controlling to resetting voltage. Resetting voltage will with on pull voltage (VPULLUP) rise into scale. And once V of prep above of power source voltagePOR, in-house MOSFET brings drive RESET the foot to enter significant position.
Voltage monitor can be used at the course of low power source of monitoring FPGA, ASIC or DSP, its voltage but low to 1V. In processor of voltage of low power supply, the logistic n of I/O is very sensitive, its VIHBut low to 0.5V, if pursue,3 are shown.
Graph 3. The interface of monitor and ASIC/FPGA/DSP of voltage of low power supply
During electrify, FPGA, ASIC or DSP need are in RESET condition, till stability of course of all power source. When VDD under VPORWhen, RESET brings a foot to may appear burr, this burr may spark the sealed condition of FPGA. Once V of VDD prep abovePOR, in-house MOSFET joins RESET with respect to meeting open GND, make RESET brings a foot to output correct logistic low n.
Graph 4. Take the electrify sequential of burr restoration signal
Develop to low-pressure semiconductor as electronic industry, imitate chip manufacturer also tries hard to come true on the foundation of traditional monitor without burr monitor. Manufacturer can reduce V through improving technologyPOR, but implementation does not have burr monitor truly to need a brand-new framework.
Current, systematic engineer uses the exterior circuit that contains traditional monitor to come to what imitate graph shows 5 times do not have burr monitoring function. Add a configuration to be source pole to follow implement standard JFET can realize this one function, the voltage of source pole will depend on the difference of grid voltage VG and voltage of JFET threshold value. Voltage meets JFET threshold value arise between VG and VOUT about of 1V pressure fall, when voltage interiorly MOSFET closes, the output that avoids monitor thereby lifts, begin normal work till the in-house MOSFET of monitor.
Graph 5. One contains the traditional monitor of exterior P-JFEF, can come true to work without burr
Do not have burr monitor truly to be able to pass restoration inspiratory electric current, even when VCC also can be stretched the foot to play ground connection potential compulsively for zero hour. Pursue the circuit of 6 give typical examples that showed one kind does not have burr monitor truly, MAX16161/MAX16162 need not any exterior component can come true to work without burr, cabinet and economy.
Graph 6. The applied sketch map of MAX16162 and corresponding sequential chart
Do not have burr monitor truly IC is a concept only no longer. Design personnel has to be able to produce the monitor IC of reliable restoration signal below voltage of 0 power source now, make systematic engineer can use this IC to come monitoring low power supply is pressed (under 1V) electronic parts. MAX16161/MAX16162 is miniature NanoPower IC, static electric current is 825nA only, conduce to prolong systematic battery life.
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