Koninklijke Philips Corporation N.v.

U.S. Philips Corporation

Abraham Klaas Van Den Heuvel

Hendrik Boezen

Ruurd Anne Visser

Aloysius Johannes Maria Boomkamp

Clemens Gerhardus Johannes De Haas

Gerrit Jan Bollen

Martinus Bredius

Patrick Willem Hubert Heuts

Cecilius Gerardus Kwakernaat

Peter Michael Buehring

Egon Joehnk

Maarten Teunis Visser

Aloysius J Boomkamp

Line driver for a LIN-bus. The line driver has a current source output transistor (T) for pulling down the LIN-bus wire (LB) to ground (GND). The LIN-bus wire (LB) is connected to a positive supply voltage (VBAT) through a pull-up resistor (R). The output transistor (T) is driven by a driver stage (DRV) in response to an input current (J) at an input node (X). The driver stage has a further resistor (R) connected between the gate of the output transistor (T) and a reference terminal (GND), a reference transistor (T) which has its source connected to the reference terminal (GND) and its drain coupled to the input node (X); the gates of the output transistor (T) and the reference transistor (T) are connected to an output (DAO) of a differential amplifier (DA) which has an inverting input (DAN) coupled to a bias voltage source (E) and a non-inverting input (DAP) coupled to the input node (X). The further resistor (R) stage provides a low-impedance path to ground for RF disturbances reaching the gate of the output transistor (T) through the drain-gate capacitance of the output transistor (T) and prevents these disturbances from penetrating the driver stage.

Line driver with current source output and high immunity to RF signals

Line driver for a LIN-bus. The line driver has a current source output transistor (T ) for pulling down the LIN-bus wire (LB) to ground (GND). The LIN-bus wire (LB) is connected to a positive supply voltage (VBAT) through a pull-up resistor (R ). The output transistor (T ) provides a ramp shaped output current under control of a ramp generator (RG). The ramp shaped output current in combination with the pull-up resistor (R ) asserts a ramp shaped output voltage on the LIN-bus wire (LB). According to the LIN-bus specifications the resistance of the pull-up resistor may vary between 500 Ohm and 1 kOhm. When the resistance is 1 kOhm, the output voltage is clamped to signal ground (GND) and a delay occurs between the edge in the data signal (TXD) and the corresponding rising ramp in the output voltage. This delay is reduced considerably by a comparator (CMP, T ) which monitors the output voltage and which increases the slew rate of the ramp generator (RG) when the output voltage is clamped and drops below a certain threshold.

Line driver with current source output and low sensitivity to load variations

A fault tolerant air bag system needs a floating supply, which supply conventionally is made by means of a DC-DC converter with a transformer. By splitting the main energy reserve capacitor ( ) into two capacitors ( ), and coupling one of the capacitors ( ) to the other ( ) by means of switches ( ) which open during a crash, no transformer is needed any more.

Fault tolerant air bag bus system without transformer

An electronic circuit having first (V ) and second (V ) power supply terminals and comprising a first digital driver (DRV) and a further digital driver (DRV ). The digital drivers (DRV, DRV ) are arranged for driving capacitive loads such as charge pump capacitors (CP , CP ) of a charge pump (CHGP). The first digital driver (DRV) comprises a first field effect transistor (T ) having a source coupled to the first power supply terminal (V ), a drain coupled for driving the first charge pump capacitor (CP ), and a gate; a second field effect transistor (T ) having a source coupled to the second power supply terminal (V ), a drain coupled to the drain of the first field effect transistor (T ), and a gate; a first capacitor (C ) coupled between the gate of the first field effect transistor (T ) and an input terminal (CLK) for receiving a digital input signal (U ); and a second capacitor (C ) coupled between the gate of the second field effect transistor (T ) and the input terminal (CLK). The further digital driver (DRV ) is constructed in a similar way as the digital driver (DRV). DC paths are formed between the gates of field effect transistors (T ) and the supply terminals (V , V ). Owing to the special construction of the digital drivers (DRV, DRV ), there is never a short-circuit current between the digital drivers (DRV, DRV ). As a result, the digital drivers (DRV, DRV ) have a very high power efficiency.

Electronic circuit provided with a digital driver for driving a capacitive load

The common mode component in the difference signal on the bus terminals (,) of a CAN bus is counteracted by four transistors (M,-M,) connected between the supply terminals (,) and a center tap (,) of a voltage divider (,A,,B,,A,,B) between the bus terminals (,). As a result of this, the voltage on the center tap (,) varies to a substantially smaller extent or not at all. Thus, it is possible to use a simpler differential amplifier (,) having a smaller common mode swing at the inputs (,). Moreover, the attenuation factor selected for the voltage divider can be smaller, as a result of which a higher difference voltage is available for the differential amplifier (,).

Circuit for suppressing a common mode component in a signal from a CAN communication bus

Bus driver having a P-channel output transistor (T1) for driving a first bus terminal (6) from a positive supply terminal (2), an N-channel output transistor (T2) for driving a second bus terminal (12) from a negative supply terminal (4), a P-channel driver transistor (T3) and an N-channel driver transistor (T4) series connected between the positive (2) and the negative (4) supply terminal. The control electrodes of the P-channel transistors (T1, T3) are interconnected and the control electrodes of the N-channel transistors (T2, T4) are interconnected to obtain a fixed relationship between the currents through the P-channel transistors (T1, T3) and through the N-channel transistors (T2, T4). The conduction of the driver transistors (T3, T4) is controlled by two floating control voltage sources (22, 24) which are connected between the interconnection node (20) of the driver transistors (T3, T4) and the respective control electrodes of the driver transistors. Any difference between the current through the P-channel driver transistor (T3) and the N-channel driver transistor (T4) is compensated for by a change in the voltage level at the interconnection node (20). In this way the currents through the driver transistors (T3, T4), and also through the output transistors (T1, T2) which are scaled copies of the driver transistors, are always equal and a highly symmetrical driving of the two bus wires (8, 14) is obtained. As a result, the electromagnetic radiation of the bus wires is low.

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Nijmegen, Netherlands

Abraham Klaas Van Den Heuvel