Auto Electronics

Linear offers 100 V step-down controller, 14-bit A/D converter

Linear Technology has introduced two devices for automotive applications, the LTC3810 step-down switching regulator controller, and the LTC1403AH, a 14-bit, 2.8 Msps successive approximation register (SAR) analog-to-digital (A/D) converter.

The company describes the LTC3810 as a high-input voltage synchronous step-down switching regulator controller that can directly step down voltages from 100 V to output voltages ranging from 0.8 V to 93% of VIN.

The part’s single inductor design eliminates the need for a transformer, and it uses a constant on-time valley current mode control architecture to deliver low duty cycles and fast transient response with accurate cycle-by-cycle current limit without requiring a sense resistor.

Onboard 1 ¿ gate drivers minimize switching transient losses associated with driving MOSFETs at high frequency and high voltage, according to the company. The switching frequency is selectable from 100 kHz to 1 MHz to optimize the size of inductors and capacitors, or the frequency can be synchronized to an external source over the same range.

Packaged in a 28-lead SSOP, the LTC3810 can be configured for pulse-skipping operation to maintain high efficiency at light loads. Its 0.8 V reference has ±0.75% accuracy from -40 °C to +85 °C. An adjustable soft-start guarantees safe start-up by eliminating turn-on overshoot, and the device has a tracking feature to control the output voltage during power up. Applications include 48 V power conversion in automotive and other systems susceptible to high-voltage surges.

Guaranteed over the -40 °C to +125 °C automotive temperature range, the LTC1403AH operates from a single 2.7 V to 3.6 V supply, draws only 14 mW at 2.8 Msps, and is available in a 10-lead MSOP package. It includes an internal reference, measures a single differential 0 V to 2.5 V input signal, and communicates via a simple three-wire serial interface. Automotive applications include baseband radar measurements, gas sensors and accelerometer sensing.

The LTC1403AH features 5 MHz full linear bandwidth and achieves 76.3 dB signal including noise and distortion (SINAD) and -90 dB spurious-free dynamic range (SFDR) at 100 kHz. While measuring 0 V to 2.5 V unipolar inputs differentially, the LTC1403AH's 80 dB common-mode rejection ratio allows users to reduce the effects of ground loops and common-mode noise. When the ADC is not converting, power dissipation can be reduced to 3 mW in Nap mode, with the internal 2.5 V reference remaining active, and 6 uW with all internal circuitry powered down in sleep mode.

The LTC1403H is a pin- and software-compatible 12-bit version of the LTC1403AH for performance/cost optimization. Both devices are specified over the H grade (-40 °C to +125 °C), I-grade (-40 °C to +85 °C) and C-grade (0 °C to +70 °C) temperature ranges. For the 14-bit LTC1403A, pricing begins at $9.65 each for H grade and $7.00 each for C grade. For the 12-bit LTC1403, pricing begins at $5.50 each for H grade and $4.00 each for C grade, all in 1,000-piece quantities.

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