Versatile Oscillators and Power-On Reset Circuit
The MAX7378 is equipped with two oscillator and a power-on reset circuit tailored for microprocessors. The Speed input serves a dual purpose: choosing between 32.768 kHz (LF) or a predetermined higher frequency. The type number signifies the standard pre-programmed value, coupled with the reset threshold. Two threshold options are available: 2.56 V and 4.29 V, applicable across all standard frequencies, including 1 MHz, 1.8432 MHz, 3.39545 MHz, 3.6864 MHz, 4 MHz, 4.1943 MHz, and 8 MHz. Notably, frequencies ranging from 600 kHz to 10 MHz are also viable. A built-in synchronization mechanism ensures seamless transitions between the two oscillators, preventing glitches.
Diverse Reset Output Options
The MAX7378 offers three Reset output configurations. Two options are push-pull types, available as either active low or active high signals. Alternatively, the third option employs an open-drain configuration, necessitating an external pull-up resistor (depicted in dashed outline connected to the Reset output). The Reset signal stays active for 100 μs after the supply voltage surpasses the threshold voltage. If the voltage falls below the threshold, the Reset signal activates instantly. Importantly, the IC is powered via two distinct pins, ensuring efficient operation.
Power Distribution and Decoupling
The functionality of the MAX7378 relies on proper power distribution: the VL pin energizes the reset and oscillator circuitry, and the VCC pin supplies power to the rest of the chip. It’s crucial to maintain the same potential across these two pins. Adequate decoupling is ensured through the inclusion of two 100-nF ceramic capacitors (SMD types). These capacitors play a pivotal role in stabilizing the circuit’s performance.
Compact Size and Package Details
The MAX7378 is packaged in an incredibly compact 8-pin μMAX package, measuring just 3.05 × 5.03 mm, including the pins, with a pin pitch of a mere 0.65 mm. Despite its diminutive size, this IC offers significant functionality, making it ideal for applications where space is at a premium.
Oscillator Accuracy and Usability
While the oscillators’ accuracy isn’t exceptional, they prove suitable for many applications. The HF oscillator exhibits an error of ±2% at 25 °C with a 5-V supply voltage, coupled with a maximum temperature coefficient of +325 ppm. Although this doesn’t align precisely with crystal accuracy, it serves well in most non-time-critical applications. However, over the entire supply voltage range (2.7–5.5 V), the error doubles. The 32.768-kHz oscillator fares slightly better, boasting a 1% error at 5 V and 25 °C. Despite this, it might still be marginally high for applications requiring precise time measurements. The error can fluctuate up to ±3% over the entire supply voltage range. Moreover, the IC demonstrates relatively low maximum current consumption, standing at 5.5 mA, contributing to its efficiency and suitability for various low-power applications.