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MC146010 数据表(PDF) 9 Page - Freescale Semiconductor, Inc |
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MC146010 数据表(HTML) 9 Page - Freescale Semiconductor, Inc |
9 / 18 page Sensors Freescale Semiconductor 9 MC146010 PIN DESCRIPTIONS C1 (PIN 1) A capacitor connected to this pin as shown in Figure 5 determines the gain of the on-chip photo amplifier during pushbutton test and chamber sensitivity test (high gain). The capacitor value is chosen such that the alarm tripped from background reflections in the chamber during pushbutton test. AV = 1+(C1/10) where C1 is in pF. CAUTION: The value of the closed-loop gain should not exceed 10,000. Resistor R15 should be installed in series with C1 for lower gains. R15 =[1/(12 √C1]-680 where R15 is in ohms and C1 is in farads. C2 (PIN 2) A capacitor connected to this pin as shown in Figure 5 determines the gain of the on-chip photo amplifier during pushbutton test and chamber sensitivity tests. AV = 1+(C2/10) where C1 is in pF. This gain increases about 10% during IRED pulse, after two consecutive local smoke detections. For proper compensation, resistor R14 must be installed in series with C2. R14 =[1/(12 √C2]-680 where R14 is in ohms and C1 is in farads. DETECT (PIN 3) This input to the high-gain pulse amplifier is tied to the cathode of an external photodiode. The photodiode should have low capacitance and low dark leakage current. The diode must be shunted by a load resistor and is operated at zero bias. The Detect input must be ac/dc decoupled from all other signals, VDD and VSS. Lead length and/or foil traces to this pin must be minimized also. See Figure 3. The device has a sampling speed-up mode after the first smoke sample is detected. The speed-up frequency is one smoke sample about every 2 seconds for the duration of a smoke condition. It will take no-smoke samples to return to a standby mode. Once out of a smoke condition, the IC will continue to sample for smoke about every 8 seconds. STROBE (PIN 4) This output provides the strobed, regulated voltage referenced to VDD. The temperature coefficient of this voltage is ±0.2%/°C maximum from -10 to 60°C. The supply-voltage coefficient (line regulation) is ±0.2%/V maximum from 6.0 to 12 V. Strobe is tied to external resistor string R8, R9 and R10. VDD (PIN 5) This pin is connected to the positive supply potential and may range from +6.0 to +12 V with respect to VSS. CAUTION: In battery-powered applications, reverse- polarity protection must be provided exter- nally. IRED (PIN 6) This output provides pulsed base current for external NPN transistor Q1 used as the infrared emitter driver. Q1 must have a β ≥ 100. At 10 mA, the temperature coefficient of the output voltage is typically +0.5%/°C from -10 to 60°C. The supply-voltage coefficient (line regulation) is ±0.2%/V maximum from 6.0 to 12 V. The IRED pulse width (active- high) is determined by external components R1 and C3. With a 100 k Ω/1500 pF combination, the nominal width is 105 µs. To minimize noise impact, IRED is active near the end of strobe pulses for smoke tests, chamber sensitivity test, and pushbutton test. For the above mentioned width, IRED will be active for the last 105 µs of strobe pulse. I/O (PIN 7) This pin can be used to connect up to 40 units together in a wired-OR configuration for common signaling. VSS is used as the return. An on-chip current sink minimizes noise pickup during non-smoke conditions and eliminates the need for an external pull-down resistor to complete the wired-OR. Remote units at lower supply voltages do not draw excessive current from a sending unit at higher supply voltage. I/O can also be used to activate escape lights, auxiliary alarms, remote alarms and/or auto-dialers. As an input, this pin feeds a positive-edge-triggered flip- flop whose output is sampled nominally every 1 second during standby (using typical component values). Once the first I/O remote smoke sample is detected, a second sample approximately 10 ms later will happen to confirm a remote smoke condition. If both samples are found to be high, the unit will start sounding an alarm. I/O is disabled by the on-chip power-on reset to eliminate nuisance signaling during battery changes or system power- up. If unused, I/O must be left unconnected. BRASS (PIN 8) This half of the push-pull driver output is connected to the metal support electrode of the piezoelectric audio transducer and to the horn-starting resistor. A continuous modulated tone from the transducer is a smoke alarm indicating either local or remote smoke. A short beep or chirp is a trouble alarm indicating a low supply or degraded chamber sensitivity. A series of short beeps or chirps during a pushbutton test indicate a previous alarm for detected smoke (Alarm memory feature). SILVER (PIN 9) This half of the push-pull driver output is connected to the ceramic electrode of a piezoelectric transducer and to the horn-starting capacitor. FEEDBACK (PIN 10) This input is connected to both the feedback electrode of a self-resonating piezoelectric transducer and the horn- starting resistor and capacitor through current limiting resistor R4. If unused, the pin must be tied to VSS or VDD. LED (PIN11) This active-low open drain output directly drives an external visible LED at the pulse rate indicated below. The pulse width is equal to the OSC period. |
类似零件编号 - MC146010 |
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类似说明 - MC146010 |
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