APPLICATIONS POWER SEMICONDUCTORS Peter Brauschke Smart power switches for industrial controls Smart power switches are available for applications in 12 and 24 V DC systems. Although they have been predominantly used so far in automotive electronics, they also satisfy the requirements of industrial automation. Industrial controls in particular open up a wide field of applications for smart power switches. load current monitoring and limiting of the driven transistors by external shunts, short-circuit cutoff, status feedback, gate-discharge resistors for driven power transistors, gate-source zener diode for driven power transistors, and protection against line breaks. Each of the four drivers has an active-high input (DI1 to DI4). An enable input (ENA) is also common to all stages. The load current is measured via the RSC shunt (Fig. 2) and limited by the respective output Q (1 to 4) if required. If the load current exceeds the set value, the connected power transistor is protected by switching to pulsed operation. It is reactivated by the built-in clock generator whose operation requires an external capacitor CE at the CE terminal. If CE is bridged by the normally closed contact of a key, it is turned on again only when the key is activated. The clock generator has a pulse/pause ratio of 1:47. A short circuit with respect to ground or excess current is displayed at the status output SQ. components from the Semiconductor Group's range of single to four-channel switches which are ideal for industrial controls. Four-channel driver IC with integrated protection The FZL 4146 is a driver IC in a standard SO-20 package designed to drive four p-channel MOSFET power transistors (Fig. 1). This component combines the ease of direct driving by microcontroller with the following features: Fig. 1 The FZL 4146 can drive four power transistors Vs 15 s microelectronics takes on more and more applications, especially in automation and automotive technology, higher performance is demanded from power switches. In many cases, these requirements can no longer be satisfied with conventional electromechanical solutions. Siemens offers a range of special components for such applications. These include an intelligent driver IC for power transistors as well as a range of smart power switches. In industrial electronics, smart power switches must deliver a level of performance similar to that required by automotive electronics. As a rule, high-side switches are required for loads connected to ground. These switches should be protected, operate over a wide range of temperatures and voltages, and, in certain applications, generate a status feedback. A CE DI1 DI2 DI3 DI4 ENA Whereas the driver IC was specially developed for industrial electronics, the smart power switches represent a selection of Components XXXI (1996) No. 3 1 T 3 & 4 & 7 & 8 2 & ENA B UV I Q 19 W1 20 Q1 I Q 17 W2 18 Q2 I Q 14 I Q 11 W4 12 Q4 TS SQ 9 TS 10 SQ 13 W3 Q3 6 16 GND GND 21 APPLICATIONS POWER SEMICONDUCTORS Mini-PROFET Type Vbb (AZ) Vbb (on) Ron (max) I L (ISO) I L (SC) Package BSP 350 BSP 450 BSP 550 >50 V >45 V >45 V 4.9 to 45 V 12 to 40 V 12 to 40 V 5V 0.2 V 0.2 V 0.07 A 1.7 A 1.7 A 0.2 A 0.7 A 1.4 A SOT 223 SOT 223 SOT 223 PROFET Type Vbb (AZ) Vbb (on) Ron (max) IL (ISO) BTS 410H2 BTS 432I2 BTS 612N1 BTS 712N1 >60 V >60 V >60 V >60 V 4.7 to 12 V 4.5 to 42 V 5 to 34 V 5 to 34 V 220 mV 38 mV 2 u 200 mV 4 u 200 mV 1.8 A 11 A 2 u 2.3 A Inon I L (SCr) I L (SCp) Package 4 u 1.9 A 1.5 A 33 A 2u4A 4u4A 5.5 A 42 A 2 u 7.5 A 4 u 7.5 A TO 220/5 TO 220/5 TO 220/7 Standard SO-20 Table 1 Selection of Mini-PROFET and PROFET types for automation applications Unused W-inputs are to be connected to VS VS VS RI int.VS CE Clock Generator W Current Regulator CE RSC R S T2 Q DI Schmitt Trigger & T1 The inputs DI, ENA and W are safeguarded against line breaks, i.e. open input DI or ENA corresponds to input L, and open input W corresponds to excess current. The maximum turn-on threshold is effective when the TS input is open. Voltage monitoring ensures that the outputs are disabled if the supply voltage is too low. Completely integrated in a minimum space 1x/Channel ENA int.VS RQ Schmitt Trigger SQ 1 X TS RL GND IED01123 Fig. 2 Driver chip FZL 4146 with integrated protective functions for four power transistors Fig. 3 The BSP 350 current-controlled switch is ideal as a signal transformer and amplifier for long leads susceptible to short circuits +Vbb 2/4 4 Control Circuit RIN 3 Temperature Sensor 2 1 IN 1 RL GND 22 OUT 3 Applications with compact modules and extensive protection functions require fully integrated components. A series of fully protected power switches for loads connected to ground (Table 1) satisfy the requirements of automation technology. They are divided into two performance classes: Mini-PROFET (for currents up to about 1.5 A) and PROFET (for currents of approximately 1.5 to 9 A). These smart power switches feature: short-circuit protection, input protection, overtemperature shutdown with hysteresis, overload protection, limitation of the negative output voltage when inductive loads are switched, undervoltage shutdown, and load current limitation. Mini-PROFETs are available as currentcontrolled or voltage-controlled switches. The BSP 350 is an example of a current-controlled switch that is particularly suitable for use as a signal transformer and amplifier for Components XXXI (1996) No. 3 APPLICATIONS POWER SEMICONDUCTORS ground may differ by any amount within the data sheet limits without impairing the function of the component. +Vbb 4 Vbb min/max 4 Control Circuit IN 3 OUT 1 3 Temperature Sensor 2 1 2 RL GND Fig. 4 The BSP 450 voltage-controlled switch offers low resistance and full protection within a minimum space Voltage Overvoltage protection source VLogic Voltage sensor 2 IN ESD Current limit +Vbb Gate protection 3 OUT Limit for unclamped ind. loads Charge pump Level shifter Rectifier Logic Open load detection 4 ST 5 Temperature sensor Load Short circuit detection GND 1 Load GND Signal GND 5 5 1 Standard TO-220AB/5 Straight leads 1 BSP 450 (Fig. 4) is a low-resistance voltagecontrolled switch with a high-resistance CMOS-compatible input in an SOT-223 package. It is turned on by a positive voltage at pin 3, while the output transistor is turned on with the aid of the integrated charge pump. The other protective functions are comparable to those of the BSP 350. As a variant of the BSP 450, the BSP 550 offers higher current limiting for loads with a greater current requirement. The functions of the PROFET switches are comparable with those of the Mini-PROFET components. All PROFETs are voltagecontrolled components with high-resistance CMOS-compatible inputs (Fig. 5). They additionally have a status output that provides information on the status of the switch or the connected load. The PROFET components BTS 410H2 (220 mV) and BTS 43212 (38 mV) are available both in TO-220/5 packages and as SMDs. The integration and packaging density of industrial controls can be increased even further by using multiple switches in a single package. Such switches are already available and include the BTS 612N1, a two-channel switch with 2 u 200 mV in a TO-220/7 package, and the BTS 712N1, a four-channel switch with 4 u 200 mV in a h standard SO-20 package. 5 SMD 1 Standard SO-20 Check #3-96-6 (HL) on Reader Service Card Fig. 5 All PROFETs are fully protected low-resistance high-side switches with a status output long feed lines susceptible to short circuits (such as for sensors or remote-controlled relays). To turn the component on, a voltage difference of at least 5 V is required between pin 2 and pin 1 (Fig. 3). The maximum operating current is only 1 mA. The current is limited to this value, i.e. it rises no further even at the maximum permissible supply voltage of 45 V. The operating current supplies the energy required for the charge pump to switch loads connected to ground. If the permissible chip temperature Components XXXI (1996) No. 3 is exceeded, the component turns off, in which case the charge pump is also deactivated. This causes a significant change in the current level at pin 1, a situation that may be used for evaluating the status. If Vbb between pin 1 and pin 2 exceeds 55 V, the component is protected by an integrated zener diode. The negative voltage peak at the output produced when inductive loads are turned off is limited to Vbb - 55 V, thus allowing rapid demagnetization of the load. The potentials of logic ground and load Peter Brauschke, Dipl.-Ing. (FH), studied electrical engineering at Augsburg and Giessen Polytechnics. In 1984 he joined Siemens in product marketing for SIPMOS transistors. From 1986 onward he helped to set up and market the Smart-SIPMOS product spectrum worldwide. Since 1995, Mr. Brauschke (39) has been responsible for product marketing of smart power switches. 23