STKNXTR

STKNX Datasheet Miniature KNX transceiver with voltage regulators and microcontroller support Features • • • • • VFQFPN24 (4 x 4 x 1.0 mm, 0.5 mm pitch) • • • • Very thin fine pitch 4 x 4 mm VQFNPN24 package KNX certified, KNX TP1-256 supported Easy interface to microcontroller Very small system solution Two integrated voltage regulators for external use in application – Selectable 3.3 V / 5 V - 20 mA linear regulator – Adjustable 1 V to 12 V - 150 mA high- efficiency DC/DC step down switching converter KNX bus power extractor supporting bus current up to 30 mA Adjustable KNX bus current slew rate dI/dt No crystal required Operating temperature range -40 °C to +85 °C Applications • KNX twisted pair network (KNX TP1-256) Description The STKNX is a transceiver device for KNX TP communication. The small package and few external components enable very compact KNX node design. Product status link STKNX Product summary Order code Package Packing STKNX STKNXTR VFQFPN24 Tube Product label Tape & Reel The simple interface to the microcontroller allows easy replacement of physical layer discrete component implementations. The STKNX device features two integrated voltage regulators for external use in the application: the selectable 3.3 V / 5 V - 20 mA linear regulator and the adjustable 1 V to 12 V - 150 mA high-efficiency DC/DC step down switching converter. The integrated KNX bus power extractor supports bus current up to 30 mA to power external devices and the STKNX transceiver's own power needs, while limiting the bus current slew rate according to KNX specifications. The STKNX ensures safe coupling to the bus and provides the bus monitoring warning for the loss of bus power. DS12399 - Rev 3 - May 2021 For further information contact your local STMicroelectronics sales office. www.st.com STKNX Typical application circuit and block diagram 1 Typical application circuit and block diagram 1.1 Typical application circuit Figure 1. Typical application circuit, buck converter enabled, linear regulator supplied by impedance modulator DCDC FB DCDC GND DCDC LX DCDC_SS DCDC IN VDDHV_PD VDDHV VREF VFLT VDD_REGIN KNX_AC VCCCORE STKNX VGATE KNX_A VCC_OK R68 KNX_OK CPH KNX_TX CPL KNX_RX VCC_SEL Note: DS12399 - Rev 3 KNX_B KNX_B VOUT range 1 V - 12 V. VCORE selectable to 3.3 V / 5 V through VCC_SEL (3.3 V in the example). page 2/27 STKNX Typical application circuit Figure 2. Typical application circuit, buck converter enabled, linear regulator supplied by buck converter DCDC FB DCDC GND DCDC LX DCDC_SS DCDC IN VDDHV_PD VDDHV VREF VFLT VDD_REGIN KNX_AC VCCCORE STKNX KNX_A VCC_OK KNX_OK R68 KNX_TX CPH KNX_RX CPL VCC_SEL Note: DS12399 - Rev 3 VGATE KNX_B KNX_B The VOUT level needs to be compliant with VDD_REGIN recommended operating conditions. VCORE selectable to 3.3 V / 5 V through VCC_SEL (3.3 V in the example). page 3/27 STKNX Typical application circuit Figure 3. Typical application circuit, buck converter disabled DCDC FB DCDC GND DCDC LX DCDC_SS DCDC IN VDDHV_PD VDDHV VREF VFLT VDD_REGIN KNX_AC VCCCORE STKNX VGATE KNX_A VCC_OK KNX_OK R68 KNX_TX CPH KNX_RX CPL VCC_SEL Note: DS12399 - Rev 3 KNX_B KNX_B VCORE selectable to 3.3 V / 5 V through VCC_SEL (3.3 V in the example). page 4/27 STKNX Typical application circuit Figure 4. Typical application circuit, linear regulator disabled DCDC FB DCDC GND DCDC LX DCDC_SS DCDC IN VDDHV_PD VDDHV VREF VFLT VDD_REGIN KNX_AC VCCCORE STKNX KNX_A VCC_OK KNX_OK R68 KNX_TX CPH KNX_RX CPL VCC_SEL Note: VGATE KNX_B KNX_B The VOUT level needs to be compliant with VCCCORE recommended operating conditions. VCC_SEL needs to be set according to the VCCCORE level (3.3 V in the example). Table 1. External components typical value Reference Type Typ. value Rating Description Capacitors CPH MLCC 100 nF VRATED ≥ 50 V Equalizer storage capacitor CPL MLCC 100 nF VRATED ≥ 50 V Equalizer storage capacitor CGATE MLCC or electrolytic 10 µF - 47 µF VRATED ≥ 10 V CAC MLCC 10 nF VRATED ≥ 50 V Bus AC coupling capacitor CVDDHV Electrolytic ≥ 100 µF VRATED ≥ 35 V Impedance modulator output bulk capacitor Impedance modulator storage capacitor - see Table 7 - see Table 7 CFH DS12399 - Rev 3 MLCC 47 nF VRATED ≥ 35 V Impedance modulator compensation capacitor page 5/27 STKNX Typical application circuit Reference Type Typ. value Rating CFL MLCC 47 nF VRATED ≥ 35 V Impedance modulator compensation capacitor CIN MLCC 10 µF VRATED ≥ 35 V Buck converter input decoupling capacitor COUT MLCC 22 µF VRATED > VOUT Buck converter output capacitor CSS MLCC 10 nF - 470 nF VRATED ≥ 6.3 V Buck converter soft-start time programming capacitor - see Eq. (3) CREF MLCC 470 nF VRATED ≥ 35 V VREF decoupling capacitor CCORE MLCC 4.7 µF VRATED ≥ 6.3 V Linear regulator output capacitor CFB1 MLCC VRATED ≥ 16 V Buck converter compensation capacitor 1/(2π * RFB1 * 28 kHz) NM if RFB1 = 0 Ω Description Resistors RDIS Resistor 4.7 MΩ - Reverse polarity discharging resistor RSH Resistor 1 kΩ - Series resistor to CPH RSL Resistor 1 kΩ - Series resistor to CPL RTX Resistor 68 Ω PDISS ≥ 1 W RFB1 Resistor RFB2 Resistor (VOUT / 1 V - 1) * RFB2 0 Ω for VOUT = 1 V 10 kΩ typ. (< 100 kΩ) NM for VOUT = 1 V Tx current limiting resistor - Buck converter output voltage adjusting resistor - Buck converter output voltage adjusting resistor Inductors L Power inductor IR > 150 mA 33 µH ISAT > 550 mA Buck converter output inductor Diodes DS12399 - Rev 3 D1 Diode LL4148 or equivalent D2 TVS SMAJ40CA or lower clamping voltage D3 Diode LL4148 or equivalent D4 Diode LL4148 or equivalent VBR > 50 V Input diode (protection from reverse VF (50 mA) < 1 V polarity connection) VBR > 50 V VF (50 mA) < 1 V Transient voltage suppressor diode Output diode Optional KNX_AC clamping diode. Recommended for noise immunity VF (50 mA) < 1 V improvement in noisy environment. VBR > 50 V page 6/27 STKNX Block diagram 1.2 Block diagram Figure 5. STKNX Block diagram DS12399 - Rev 3 page 7/27 STKNX Pin connection and pin description 2 Pin connection and pin description 2.1 Pin connection Figure 6. Pin connection (top view) 2.2 Pin description Table 2. STKNX Pin description Pin Pin name 1 VDD_REGIN 2 KNX_AC 3 R68 4 KNX_B 5 CP_H Equalization cap connection to KNX supply (KNX+) 6 CP_L Equalization cap connection to KNX ground (KNX-) 7 VFLT Impedance modulator compensation 8 VREF Impedance modulator reference 9 VDDHV 10 DS12399 - Rev 3 Function Linear regulator supply input. Short to VCCCORE to disable the linear regulator and supply VCCCORE externally. BUS AC-coupled sense for the Rx input and Tx feedback. DC biased to 9.7 V typ. KNX transmitter output Analog ground VDDHV supply input and impedance modulator feedback VDDHV_PD Impedance modulator power output 11 KNX_A KNX power supply input (KNX+) 12 KNX_B Analog ground 13 VGATE Impedance modulator storage capacitor connection page 8/27 STKNX Pin description Pin Pin name 14 DCDC_IN Step down converter supply input. Short to ground or leave floating to disable the switching converter. 15 DCDC_LX Step down converter switching output 16 Function DCDC_GND Step down converter power ground 17 DCDC_SS Step down converter soft-start programming pin 18 DCDC_FB Step down converter feedback input. Sets output voltage (1 V - 12 V range) through the resistor divider. 19 VCC_OK 20 VCCCORE 21 KNX_OK 22 VCC_SEL 23 KNX_RX Receiver CMOS digital output 24 KNX_TX Transmitter digital input. Internally pulled down (6 µA typ.). VCCCORE power good CMOS digital output Linear regulator output (3.3 V / 5 V selectable). Supply voltage for digital I/O. KNX bus power good CMOS digital output Selects linear regulator output voltage. Internally pulled down (6 µA typ.). Tie to VCCCORE to select 5 V. Short to ground or leave floating to select 3.3 V. Connect to analog ground. - DS12399 - Rev 3 Exposed pad For thermal optimization, maximize the area of the ground layer on which the exposed pad is soldered and provide good thermal connection with the bottom ground layer through vias. page 9/27 STKNX Thermal characteristics 3 Thermal characteristics Table 3. Thermal characteristics DS12399 - Rev 3 Symbol Parameter Test condition Value Unit TJ Maximum operating junction temperature - 110 °C TAMB Operating ambient temperature - -40 to 85 °C TSTG Storage temperature - -50 to 150 °C RthJA Thermal resistance junction to ambient, steady state 35 °C/W Mounted on a 2s2p PCB, with a dissipating surface connected through vias on the bottom side of the PCB. page 10/27 STKNX Electrical specifications 4 Electrical specifications 4.1 Absolute maximum ratings Table 4. Absolute maximum ratings Symbol Parameter KNX_A VDD_REGIN VDDHV VREF Min. Max. Unit KNX supply input -0.3 45 V Linear regulator supply input -0.3 40 V VDDHV supply input and impedance modulator feedback -0.3 40 V Impedance modulator reference -0.3 40 V -0.3 0.3 V KNX_B, DCDC_GND Variation between different ground pins CP_H Equalizing cap. high -0.3 KNX_A + 0.3 V CP_L Equalizing cap. low -0.3 KNX_A + 0.3 V R68 KNX transmitter output -0.3 KNX_A + 0.3 V KNX_AC BUS AC-coupled sense -0.3 KNX_A + 0.3 V VDDHV_PD Impedance modulator power output -0.3 KNX_A + 0.3 V VGATE Impedance modulator coupling cap. Max. (-0.3, KNX_A - 7.2) KNX_A + 0.3 V Linear reg. output. I/O supply. -0.3 5.5 V KNX_TX Transmitter digital input -0.3 Min. (5.5, VCCCORE + 0.3) V KNX_RX Transmitter digital output -0.3 Min. (5.5, VCCCORE + 0.3) V KNX_OK KNX bus power good -0.3 Min. (5.5, VCCCORE + 0.3) V VCC_SEL 3.3 V / 5 V selection for linear reg. -0.3 Min. (5.5, VCCCORE + 0.3) V VCC_OK VCCCORE power good -0.3 Min. (5.5, VCCCORE + 0.3) V Impedance modulator compensation -0.3 5.5 V VCCCORE VFLT 4.2 DCDC_IN Step down converter input -0.3 40 V DCDC_LX Step down converter switching node -0.3 Min. (40, DCDC_IN + 0.3) V DCDC_FB Step down converter feedback -0.3 3.6 V DCDC_SS Step down converter soft-start programming pin -0.3 3.6 V Recommended operating conditions Table 5. Recommended operating conditions Symbol Parameter Min. Max. Unit - 20 32 V VCCCORE I/O supply and linear reg. output - 3 5.5 V DCDC_IN Step down converter input - 13 32 V VCC_SEL shorted to GND 6.8 32 V KNX_A KNX supply VDD_REGIN Linear regulator supply input(2) DS12399 - Rev 3 Test condition input(1) page 11/27 STKNX Electrical characteristics Symbol Parameter Test condition Min. Max. Unit VCC_SEL shorted to VCCCORE 8.5 32 V Continuous output current from VDDHV pin(3) - - 30 mA IREG Continuous output current from VCCCORE pin(3) - - 20 mA IDCDC Continuous output current from DCDC switching converter (3) - - 150 mA VDD_REGIN Linear regulator supply input(2) IVDDHV_PD 1. Indicates DC value. With the active and equalization pulse bus voltage must be between 11 V and 45 V. 2. Short VDD_REGIN to VCCCORE to disable the internal linear regulator and provide VCCCORE voltage externally. 3. The maximum current capability refers to the voltage regulator only. The usable current capability can be limited by the KNX bus current consumption specification. 4.3 Electrical characteristics Table 6. Electrical characteristics Parameters given for a device operating within the recommended operating conditions, unless otherwise specified. Typical values are referred to TJ = 27 °C. Symbol Parameter Conditions Min. Typ. Max. Unit Power supply DC supply voltage on KNX_A pin Excluding active and equalization pulse 20 - 32 V Bus current consumption, no load V(KNX_A) = 32 V, no activity on bus, no transmission, no external load - 1 - mA Bus current consumption, 30 mA load V(KNX_A) = 32 V, no activity on bus, no transmission, 30 mA load on VDDHV rail (including linear regulator and switching converter) - 31 - mA KNX_OKRIS (VREF) KNX_OK rising threshold referred to VREF voltage VREF rising - - 13.5 V KNX_OKFALL (VREF) KNX_OK falling threshold referred to VREF voltage VREF falling 9.7 - - V KNX_OKHYST (VREF) KNX_OK hysteresis referred to VREF voltage - - 1.4 - V KNX_OKRIS (KNX_A) KNX_OK rising threshold referred to KNX_A DC voltage KNX_A rising slowly, VREF settled - - 18.5 V V(KNX_A) I(KNX_A) Impedance modulator VDDHV drop V(KNX_A) - V(VDDHV) voltage drop V(KNX_A) = 20 V DC ILOAD = 5 mA D3 = LL4148 or equivalent - - 6.5 V VDDHV drop V(KNX_A) - V(VDDHV) voltage drop V(KNX_A) = 20 V DC, ILOAD = 30 mA, D3 = LL4148 or equivalent - - 7.2 V V(KNX_A) - V(REF) voltage drop V(KNX_A) = 20 V DC, VREF settled 3 4.3 5 V 3 3.3 3.6 V VCC_SEL shorted to VCCCORE 4.5 5 5.5 V VCC_SEL shorted to GND 2.3 - 2.8 V VREF drop VCCCORE voltage and linear regulator DS12399 - Rev 3 VCCCORE Regulated voltage VCC_OKRIS VCC_OK rising threshold VCC_SEL shorted to GND page 12/27 STKNX Electrical characteristics Symbol Parameter VCC_OKRIS VCC_OK rising threshold VCC_OKFALL VCC_OK falling threshold VCC_OKHYST VCC_OK hysteresis IVCCSEL VCCSEL internal pull- down current Conditions Min. Typ. Max. Unit VCC_SEL shorted to VCCCORE 3.3 - 4 V VCC_SEL shorted to GND 2.0 - 2.5 V VCC_SEL shorted to VCCCORE 2.9 - 3.6 V VCC_SEL shorted to GND - 0.3 - V VCC_SEL shorted to VCCCORE - 0.4 - V - - 6 - µA Programmable DC-DC switching converter VIN Input voltage at DCDC_IN pin - 13 - 32 V VOUT Output voltage adjusting range - 1 - 12 V VFB Feedback voltage reference - 0.9 1 1.1 V UVLORIS Undervoltage lockout rising threshold on VIN voltage VIN rising 9 10 11 V UVLOFALL Undervoltage lockout falling threshold on VIN voltage VIN falling 5.4 6 6.6 V UVLOHYST Undervoltage lockout hysteresis on VIN voltage - - 4 - V ILIM High side MOSFET current limit - 325 650 975 mA - 50 - mV - 1.9 - - 1.2 - 110 140 - °C VOUT_RIP Output voltage ripple 13 V < VIN < 32 V 3.3 V < VOUT < 12 V IOUT = 5 mA ~ 150 mA COUT = 22 µF RDS(ON) High side MOSFET on resistance MLCC(1) - Low side MOSFET on resistance temperature(2) Ω OTP Overtemperature protection Junction OVPRIS Overvoltage protection rising threshold on FB FB voltage rising 1.1 1.25 1.4 V OVPFALL Overvoltage protection falling threshold on FB FB voltage falling 0.95 1.1 1.25 V ISS Current sourced from SS pin During soft-start - 2.5 - µA Transmitter RDS(ON) Tx MOSFET on resistance - - 5 - Ω IKNX_TX KNX_TX internal pull- down current - - 6 - µA VCCCORE = 3.3 V 0.7 - - VCCCORE = 5 V 1.2 - - - - 2.2 - - 3 VCCCORE = 3.3 V ISUNK = 300 µA 0 - 0.4 V VCCCORE = 5 V ISUNK = 400 µA 0 - 0.4 V Digital I/Os VIL Maximum voltage level that will be interpreted as a logic 0 VIH Minimum voltagelevel that will be VCCCORE = 3.3 V interpreted as a logic 1 VCCCORE = 5 V VOL DS12399 - Rev 3 Logic low output level V V page 13/27 STKNX Electrical characteristics Symbol VOH Parameter Logic high output level Conditions Min. Typ. Max. Unit VCCCORE = 3.3 V, ISOURCED = 300 µA VCCCORE - 0.5 - VCCCORE V VCCCORE = 5 V, ISOURCED = 400 µA VCCCORE - 0.5 - VCCCORE V 1. Not tested in production. Guaranteed by design. 2. Not tested in production. Based on characterization. DS12399 - Rev 3 page 14/27 STKNX Device description 5 Device description The STKNX is a transceiver device for twisted pair communication, following the KNX twisted pair standard (KNX TP1-256). Detailed information on the KNX bus can be found in the KNX standards and on the KNX website (www.knx.org). The STKNX is composed of two main functional blocks: the bus interface and the voltage regulators. • The bus interface consists of the transmitter, receiver and impedance modulator • The voltage regulators block consists of an adjustable output voltage step down switching converter with integrated power MOSFETs and a 3.3 V / 5 V programmable linear regulator Figure 7. KNX bus voltage and corresponding digital signals VBUS Veq DC level Vact Active pulse t Equalization pulse Logic 0 35 Logic 1 69 104 104 KNX_RX KNX_TX (if transmitting) 5.1 Bus interface The bus interface connects the STKNX to the KNX bus for transmitting, receiving and extracting power. Through the bus interface, the STKNX supports • Interfacing a microcontroller with the KNX bus, translating signals between the logic level domain and KNX bus domain • Extracting power from the bus to supply the STKNX itself, the microcontroller and application devices The KNX standard specifies a bit period of 104 µs. It defines the logic 1 as the idle state of the bus (DC voltage level between 21 V and 32 V), the logic 0 (also called active pulse) as a voltage drop of the bus. The active pulse is generated by the transmitter. Ideally, the drop has a rectangular shape, a depth between 6 V and 9 V and a duration of 35 µs. Each active pulse is followed by an equalization phase of 69 µs typical duration, which consists in an overshoot of the bus voltage above the DC level, followed by an exponential decay. See the KNX Twisted Pair Standard (KNX TP1-256) for more detailed information. DS12399 - Rev 3 page 15/27 STKNX Voltage regulators 5.1.1 Transmitter The transmitter converts logic level signals received at the KNX_TX pin to analog signals on the KNX bus. To transmit a logic 1 (equivalent to transmitter in idle state), the KNX_TX pin has to be kept low for 104 µs. To transmit a logic 0, the KNX_TX has to be forced high for 35 µs (active pulse) and then low for 69 µs. During the active pulse, the transmitter forces a voltage drop of 7.5 V typ. on the KNX bus, by sinking current through the R68 pin. 5.1.2 Receiver The receiver detects the beginning and the end of the active pulse and provides a logic level output on the KNX_RX pin. The KNX_RX pin is high during the active pulse, low during the equalization phase and idle state. The detection threshold for the start of the active pulse is 0.6 V typ. below the bus DC voltage. 5.1.3 Impedance modulator The KNX standard allows a bus voltage ranging from 21 V to 32 V (DC component). The bus provides supply for the STKNX and is the communication medium. During transmission, a -10.5 V / +13 V AC component can be superimposed to the DC component mentioned above. Moreover, the KNX standard specifies that each module connected to the bus has to show a controlled impedance and to limit the bus load current slope dI/dt, while not transmitting. The impedance modulator purpose is to extract power from the KNX bus in order to supply STKNX integrated voltage converters and the application on the KNX module, while ensuring compliance to KNX impedance specifications. In particular, impedance modulator: • Extracts a stable power rail (VDDHV) from the KNX bus DC level • Smooths any load change applied at its output, limiting dI/dt on the bus current • Controls the impedance of the bus device during the active pulse and the equalization pulse according to KNX standard requirements Since the current drawn from the bus must change very slowly, abrupt load current steps from the load applied to the STKNX have to be absorbed by the large filter capacitor on VDDHV rail (CVDDHV on Figure 1), which should be sized accordingly. The bus current slope limit is controlled through CGATE (Figure 1). CGATE = 47 µF sets a slope lower than 0.5 mA/ms, compliant to the KNX requirement for fan in model up to the 10 mA bus load. For a higher fan in, it can be useful to set a higher current slope limit, in order to manage wider load changes minimizing the CVDDHV value. That can be done by reducing the CGATE value proportionally to the desired slope limit increase. Table 7 shows recommended CGATE and CVDDHV values for the minimum and maximum fan in. Table 7. Recommended CGATE and CVDDHV vs. fan-in 5.2 Fan in Recommended CGATE Recommended minimum CVDDHV 10 mA 47 µF 100 µF 30 mA 10 µF - 47 µF 220 µF Voltage regulators The STKNX features two integrated voltage regulators for external use in the application: • a linear regulator with 3.3 V or 5 V selectable output voltage, 20 mA current capability • a step down switching converter with 1 V - 12 V adjustable output voltage, 150 mA current capability. 5.2.1 3.3 V / 5 V linear regulator The linear regulator converts the input voltage on the VDD_REGIN pin to 3.3 V or 5 V output on the VCCCORE pin. The output voltage level is selectable by the VCCSEL pin. DS12399 - Rev 3 page 16/27 STKNX Voltage regulators • • VCCSEL tied to GND → VCCCORE = 3.3 V VCCSEL tied to VCCCORE → VCCCORE = 5 V VCCSEL should not be changed when STKNX is operational. The output current capability is 20 mA. A 4.7 µF capacitor or higher is required between VCCCORE and KNX_B for stability. VCCCORE is also the supply input for STKNX digital I/Os. The linear regulator can be disabled by shorting VCCCORE to VDD_REGIN; in that case VCCCORE voltage to supply I/Os has to be provided externally and VCCSEL has to be configured according to the voltage level (3.3 V or 5 V). 5.2.2 Buck converter The STKNX integrates a high-efficiency low-consumption buck switching converter. The switching converter is supplied from the DCDC_IN pin, connected to VDDHV rail in the typical application. When voltage at the DCDC_IN pin is lower than UVLO, the switching converter is disabled. Buck converter output voltage is adjustable between 1 V and 12 V by means of an external resistor divider on the DCDC_FB pin, according to the following expression: Vout = 1V ⋅ 1 + RFB1/RFB2 (1) Where RFB1 and RFB2 are the upper and lower resistor of the divider respectively (see Figure 1). The RFB2 typical value is 10 kΩ (RFB2 values higher than 100 kΩ should be avoided). To set VOUT = 1 V, RFB1 should be 0 Ω and RFB2 not mounted. In the usual case of the low ESR ceramic capacitor as the output capacitor for the converter, it is recommended to add an external feedforward compensation capacitor CFB1 in parallel to RFB1, for VOUT > 1 V. The CFB1 default value can be calculated according to the following expression: CFB1 = 1 2π ⋅ RFB1 ⋅ 28kHz (2) The buck converter can deliver a continuous output current up to 150 mA, however the maximum current capability will not always be usable. In fact, at the application level, the KNX bus current consumption must stay within the KNX specification. The buck converter implements soft-start to prevent a high inrush current at start-up. Soft-start time TSS is programmable through the external capacitor CSS between the DCDC_SS pin and GND, according to the following expression: where ISS is 2.5 µA typ. C TSS = 1V ⋅ SS ISS (3) The buck converter features a full set of protections, which includes overtemperature protection (OTP), overcurrent protection (OCP) and overvoltage protection (OVP). DS12399 - Rev 3 page 17/27 STKNX Layout recommendations 6 Layout recommendations PCB layout is an important part of DC-DC switching converter design. A poor board layout can compromise important parameters of the DC-DC converter such as efficiency, output voltage ripple, line and load regulation and stability. Good layout for the STKNX can be implemented by following the few simple design rules listed in this section. These rules have been applied to the STKNX routed area on the STKNX evaluation board (EVALKITSTKNX), where only the TOP and BOTTOM layers have been used from the four available, so it can be transposed on a low cost 2-layer PCB. It is then easy to implement the rules on a final KNX product. The source files of EVALKITSTKNX PCB layout are available for download from www.st.com. Figure 8. STKNX area routed using top and bottom layers only Refer to Figure 9 and Figure 10 below for the recommendations described below: • Place CIN (C13) close to the STKNX and connect it between pins VIN and DCDC_GND directly on top layer (DCDC_LX trace crosses between CIN pads) • Connect COUT (C24) to DCDC_GND directly on top layer • Keep the following power loops short: – CIN → DCDC_IN → DCDC_LX → L1 → COUT → CIN (green) – COUT → DCDC_GND → DCDC_LX → L1 → COUT (red) – CIN → DCDC_IN → DCDC_GND → CIN (purple) • Use properly sized traces or shapes for power paths (DCDC_IN, DCDC_GND, VDCDC, LX) – Keep FB/Feedback and SS/Soft-Start components (Rfbx, Cfb1, Css) away from switching / noisy node (DCDC_LX), shielding with quiet nets (DCDC_GND in the image) is recommended (black) – Connect DCDC_GND pin (16) and KNX_B pins (4 and 12) to the exposed pad shape below the IC, as shown in Figure 10, to ensure ground consistency – Place several GND vias on STKNX package exposed pad (x9 in EVALKITSTKNX). DS12399 - Rev 3 page 18/27 STKNX Layout recommendations Figure 9. Layout recommendations description Figure 10. Layout recommendations application DS12399 - Rev 3 page 19/27 STKNX Package information 7 Package information In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK packages, depending on their level of environmental compliance. ECOPACK specifications, grade definitions and product status are available at: www.st.com. ECOPACK is an ST trademark. 7.1 VFQFPN 4 x 4 x 1.0 24 pitch 0.5 package information Figure 11. VFQFPN 4 x 4 x 1.0 24 pitch 0.5 package outline DS12399 - Rev 3 page 20/27 STKNX VFQFPN 4 x 4 x 1.0 24 pitch 0.5 package information Table 8. VFQFPN 4 x 4 x 1.0 24 pitch 0.5 package mechanical data Symbol DS12399 - Rev 3 Dimensions [mm] Min. Nom. Max. A 0.80 - 1.00 A1 0.00 - 0.05 A2 - 0.65 - A3 - 0.20 - b 0.20 0.25 0.30 D 3.9 4.0 4.1 D2 2.7 2.8 2.9 e - 0.5 - E 3.9 4.0 4.1 E2 2.7 2.8 2.9 L 0.30 0.35 0.40 k 0.20 - - N - 24 - Symbol Tolerance of form and position [mm] aaa 0.15 bbb 0.10 ccc 0.10 ddd 0.05 eee 0.08 fff 0.10 page 21/27 STKNX VFQFPN 4 x 4 x 1.0 24 pitch 0.5 package information Figure 12. Suggested footprint DS12399 - Rev 3 page 22/27 STKNX Revision history Table 9. Document revision history Date Version 08-Feb-2018 1 Changes Initial release. Throughout document: 06-Dec-2020 2 - layout and template changes - minor text edits Added Section 6 Layout recommendations 20-May-2021 DS12399 - Rev 3 3 Change to Equation 1 in Section 5.2.2 page 23/27 STKNX Contents Contents 1 2 Typical application circuit and block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1 Typical application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Pin connection and pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3 Thermal characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 4 Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 5 4.1 Absolute maximum ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.2 Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.3 Electrical characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Device description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 5.1 5.2 Bus interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.1.1 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.1.2 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.1.3 Impedance modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Voltage regulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.2.1 3.3 V / 5 V linear regulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.2.2 Buck converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6 Layout recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 7 Package information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 7.1 VFQFPN 4 x 4 x 1.0 24 pitch 0.5 package information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 DS12399 - Rev 3 page 24/27 STKNX List of figures List of figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. DS12399 - Rev 3 Typical application circuit, buck converter enabled, linear regulator supplied by impedance modulator . Typical application circuit, buck converter enabled, linear regulator supplied by buck converter . . . . . . Typical application circuit, buck converter disabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Typical application circuit, linear regulator disabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . STKNX Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pin connection (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . KNX bus voltage and corresponding digital signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . STKNX area routed using top and bottom layers only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Layout recommendations description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Layout recommendations application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VFQFPN 4 x 4 x 1.0 24 pitch 0.5 package outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Suggested footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 . 3 . 4 . 5 . 7 . 8 15 18 19 19 20 22 page 25/27 STKNX List of tables List of tables Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. External components typical value . . . . . . . . . . . . . . . . . . STKNX Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . Thermal characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . Recommended operating conditions. . . . . . . . . . . . . . . . . Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . Recommended CGATE and CVDDHV vs. fan-in . . . . . . . . VFQFPN 4 x 4 x 1.0 24 pitch 0.5 package mechanical data . Document revision history . . . . . . . . . . . . . . . . . . . . . . . . DS12399 - Rev 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . 8 10 11 11 12 16 21 23 page 26/27 STKNX IMPORTANT NOTICE – PLEASE READ CAREFULLY STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, enhancements, modifications, and improvements to ST products and/or to this document at any time without notice. Purchasers should obtain the latest relevant information on ST products before placing orders. ST products are sold pursuant to ST’s terms and conditions of sale in place at the time of order acknowledgement. Purchasers are solely responsible for the choice, selection, and use of ST products and ST assumes no liability for application assistance or the design of Purchasers’ products. No license, express or implied, to any intellectual property right is granted by ST herein. Resale of ST products with provisions different from the information set forth herein shall void any warranty granted by ST for such product. ST and the ST logo are trademarks of ST. For additional information about ST trademarks, please refer to www.st.com/trademarks. All other product or service names are the property of their respective owners. Information in this document supersedes and replaces information previously supplied in any prior versions of this document. © 2021 STMicroelectronics – All rights reserved DS12399 - Rev 3 page 27/27