Tim Claycomb
(Note: Thomas Foster and Esteban Garcia co-authored this technical article.)
In 1976, National Semiconductor (now TI) introduced the LM2904, one of the most popular operational amplifiers (op amps) worldwide. It was a time when 8-track tapes played your favorite tunes in the car, a vehicle could get you an average of 14.22 miles to the gallon, and people used paper travel maps to navigate roads unfamiliar. To say the least, the world was a much different place when this op amp was released.
After the creation of the Automotive Electronics Council (AEC) in 1993, TI released the LM2904-Q1 op amp in 2003. This automotive-qualified version found its way into applications such as media interfaces, electric power steering and battery control modules.
Now, after 17 years, the LM2904-Q1 has received a performance boost with the new LM2904B-Q1 automotive op amp, designed to help you meet the evolving needs of today’s vehicles. The timeline in Figure 1 includes just a few facts illustrating the changes to both automobiles and the driving experience.
The LM2904B-Q1 complies with all AEC-Q100 standards and includes improvements such as increased performance, improved electrostatic discharge (ESD) specifications, and the integration of electromagnetic interference (EMI) filters and industry-leading data collection with characterization. The device also costs less and has faster manufacturing lead times.
Table 1 compares the LM2904-Q1 and LM2904B-Q1. As shown, there have been many performance improvements made to the new B version.
LM2904-Q1 | LM2904B-Q1 | |
---|---|---|
Total supply voltage (V) | 3 - 26 | 3 - 36 |
Gain bandwidth (MHz) | 0.7 | 1.2 |
Slew rate (typical) (V/µs) | 0.3 | 0.5 |
Vos (offset voltage at 25°C, maximum) (mV) | 7 | 3 |
IQ per channel (typical) (mA) | 0.35 | 0.3 |
Vn at 1kHz (typical) (nV/√Hz) | 40 | 40 |
Offset drift (typical) (µV/°C) | 7 | 4 |
Output current (typical) (mA) | 30 | 30 |
CMRR (typical) (dB) | 80 | 100 |
The AEC-Q100 ESD standard includes ESD ratings for the human body model (HBM) and charged device model (CDM) values of 2 kV and 750 V, respectively. Devices designed by TI and other semiconductor suppliers back in the 1970s do not meet these standards. The few semiconductor suppliers whose LM2904-Q1 variant meets the AEC-Q100 ESD standard comes at a premium price. The LM2904B-Q1, however, not only meets ESD standards but does so at a cost less than the previous version. Table 2 compares the ESD ratings of the LM2904B-Q1 and LM2904-Q1.
ESD model | LM2904-Q1 | LM2904B-Q1 |
---|---|---|
Human-body model (HBM), per AEC Q100-002 (V) | ±1,000 | ±2,000 |
Charged-device model (CDM), per AEC Q100-011 (V) | ±500 | ±750 |
Devices in automotive designs tend to experience high levels of EMI given the increased system complexity. To combat this, TI added integrated EMI filters to the LM2904B-Q1 to increase the electromagnetic interference rejection ratio (EMIRR) performance. Figure 2 compares the EMIRR performance of the LM2904-Q1 and LM2904B-Q1. A higher level in the graph corresponds to a higher level of attenuation of the EMI signal. As the graph shows, the LM2904B-Q1 rejects more EMI signals than the LM2904-Q1. For more information on EMIRR, see the application report, “EMI Rejection Ratio of Operational Amplifiers (With OPA333 and OPA333-Q1 as an Example).”
You would probably agree that with the saying, “There’s no such thing as too much information.” That’s why TI provides 38 graphs detailing the LM2904B-Q1’s device performance in the data sheet, making it one of the most well-characterized standard op amps in the industry. All of the graphs provide insight into what you can expect when using – and making appropriate system-level decisions with – the LM2904B-Q1.
Advancements in process technology and increased wafer diameters, along with improvements to the underlying wafer technology flow, allow TI to produce the LM2904B-Q1 at competitive quality and cost, and with a commitment to product longevity and assurance of supply.
The next-generation LM2904B-Q1 automotive op amp takes a huge step in the right direction, with improved ESD performance, increased EMIRR capabilities and significant characterization for easier integration into any automotive system. To B or not to B? The answer to Hamlet’s existential question becomes clear with the LM2904B-Q1.
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