a4231 general features The a4231 is a proximity sensor integrated circuit to be used with a broad range of inductive single-coiled proximity transducers in proximity detection applications Monolithic IC in bipolar technology User-adjustable sensing range by means of a single external resistor User-adjustable hysteresis (0…15%) 5.5V…35V broad supply voltage range Low-voltage operation possible using stabilised 4.5V…5.5V voltage source Internal voltage regulator to improve immunity against fluctuations of supply voltage Broad operating temperature range: -25°C...90°C Can work with a broad selection of inductive transducers NPN open collector output with guaranteed sink current of 150mA Output overload/over current protection Integrated power-on and detect LED drivers Normally open(NO)/normally closed(NC) select pin Broad range of operating frequencies: 100kHz…1MHz Output over current and short-circuit protection Easy temperature compensation of proximity transducers Package – QFN-24 example application schematic min. 2.2uF/40V electrolytic RF CF 100nF/6.3V 10% Inductive Transducer Vcc NO/NC RF NO/NC 220nF/6.3V 20% ceramic CB VCC L1 L P_LED C RES a4231 L2 D_LED 220nF/6.3V 20% OutN Rref 91kohm GND Rhyst, 5% (optional) GND1 RH C DET Cdet, 10% (optional) C OVL Covl, 10% 100nF/6.3V RSN RS,N 1R6 5% 125mW Typical application schematic of a proximity sensor/detector OutN electrical characteristics DC Characteristics The typical values are given for VCC =24V and Tj = 25°C unless otherwise specified. # Symbol Parameter 1 IVCC,OFF Supply current 2 IVCC,ON 3 VSAT,OUT 4 ILED LED current 5 ILKG Output leakage current 6 ITH,OVL Conditions Min Typ Max Unit Output inactive (off) 3.8 4.8 mA Supply current Output active (on) 8.5 12 mA Output saturation voltage IOUT=150mA 0.50 0.70 V 1.2 1.6 mA <1 20 μA 190 220 mA 1.0 Overload threshold current*1) 158 *1) –overload threshold current is the level of the output current which triggers the overload protection circuit. AC and Timing Characteristics The typical values are given for VCC =24V and Tj = 25°C unless otherwise specified. # Symbol Parameter Conditions 1 fOSC Operating frequency 2 RN Negative resistance RN= –2·RF +/-3% between pin L1 and ground 3 fMAX Maximum switching frequency*1) 4 HW 5 Defined by external LC tank Min Typ Max Unit 0.1 1.0 MHz -200 -2 kΩ CDET=4.7pF, fOSC=600kHz 5 CDET=33pF fOSC=100kHz 2 kHz Depends on RHYST tR Hysteresis width Output rise time Load=1kohm <1.5 μs 6 tF Output fall time* Load=1kohm <1 μs 7 TS,OVL 8 TSTARTUP Startup time*3) 10 CIN 2) Sampling period in overload mode Input capacitance Depends on COVL Measured between Pin L1 and AC ground (Pin L2) for fOSC=0.2…1MHz and |RN| =2…100kohm 0 15 % 50 120 250 ms 50 120 250 ms 6 8.5 13 pF *1) – these are maximum switching frequencies of the IC itself; switching frequencies of sensors may be higher than those given above, *2) – the fall time on leaving the start-up interval depends on the load used and can be as long as 10ms, *3) – this is the maximum start-up time of the chip itself; this parameter does not reflect performance of a sensor; during the start-up interval the output is inactive (OFF) regardless of the state of the NO/NC pin.