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Method for Reading External Resistor Value with High DPI Immunity

IP.com Disclosure Number: IPCOM000169634D
Original Publication Date: 2008-May-08
Included in the Prior Art Database: 2008-May-08
Document File: 4 page(s) / 48K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

In order to regulate the switching speed of low side switches, e.g. BTS 3256, devices are provided with an external resistor and a circuit which generates a current proportional to the external resistor value, as shown in Figure 1. This method can not ensure full functionality of the device under DPI test condition (Direct Power Injection; IEC 62132-4) for measuring immunity of ICs (Integrated Circuit) to conducted continuous-wave interference because the RF (Radio Frequency) disturbances (~1MHz) injected in the component pad are not filtered.

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Method for Reading External Resistor Value with High DPI Immunity

Idea: Carlo Piloto, IT-Padova; Franco, Mognoli, IT-Padova

In order to regulate the switching speed of low side switches, e.g. BTS 3256, devices are provided with an external resistor and a circuit which generates a current proportional to the external resistor value, as shown in Figure 1. This method can not ensure full functionality of the device under DPI test condition (Direct Power Injection; IEC 62132-4) for measuring immunity of ICs (Integrated Circuit) to conducted continuous-wave interference because the RF (Radio Frequency) disturbances (~1MHz) injected in the component pad are not filtered.

At present, the performance of the switch is improved by placing filter capacitors as shown in Figure 2. Nevertheless, this solution is not practicable due to required large capacities. There are other solutions known which use very fast operational amplifiers (see Figure 3) or an additional current mirror to filter conducted EMI (Electromagnetic Interference) as depicted in Figure 4.

A novel solution is proposed which ensures full functionality of the device while switching, for PWM (Pulse Width Modulation) and under DPI test condition. The proposed circuit, as shown in Figure 5, generates the current proportional to the external resistor value using an operational amplifier with very slow slew rate. The Pad is connected before the operational amplifier. The output stage drives a pmos (p-channe...