Precision Bidirectional Current Sense for Motor & Solenoid Applications
Linear Technology announced the LT1999, a high-voltage amplifier designed for bidirectional current sensing in the presence of fast switching common-mode voltages from -5V to 80V. This wide input common-mode range is obtained with standard low voltage op amp supplies. A 2MHz bandwidth enables the LT1999 to monitor currents in H-bridge motor controls, switching power supplies, solenoid, and battery chargers. To maintain outstanding accuracy, even when monitoring motor and solenoid current, the LT1999 guarantees more than 80dB of common-mode rejection at 100kHz. This ensures that the LT1999 remains insensitive to the large square wave input common-mode voltages present in these applications. The LT1999 features a buffered output with three fixed-gain options for 10V/V, 20V/V and 50V/V. By default, the LT1999 output voltage is referenced halfway between the supply voltage and ground, enabling the output to indicate both the magnitude and direction of the sensed current. In addition, the output bias level can be set via a separate input. Gain error is guaranteed at less than 0.5% and input offset voltage is guaranteed at less than 1.5mV over the full temperature range of -40°C to 125°C. The LT1999 operates with an independent 5V supply voltage, drawing only 1.5mA while active and only 10μA in shutdown mode. "The outstanding AC performance ensures smooth, continuous operation over the entire common mode range," says Mike Kultgen, Design Manager for Linear Technology. "And the differential amplifier architecture makes the LT1999 adaptable to a wide range of applications." Summary of Features: LT1999
Linear Technology Corporation announced the LT3692, a monolithic, dual output step-down switching regulator that can deliver up to 3.5A of continuous output current from each channel. It operates from a VIN range of 3V to 36V with transient protection to 60V, making it ideal for load dump and cold-crank conditions found in automotive applications. Independent input, shutdown, feedback, soft-start, current limit and comparator pins for each channel simplify complex power supply tracking/sequencing requirements. The LT3692's switching frequency is user programmable from 250kHz to 2.25MHz, enabling the designer to optimize efficiency while avoiding critical noise-sensitive frequency bands. To optimize efficiency and component size, both internal converters have a programmable maximum current limit and are synchronized to each other via the device's internal oscillator or an external clock input. The converters are run 180° out of phase to further reduce voltage ripple and external component size. Multiple regulators can be synchronized via an external clock output to provide additional voltage rails. Conversely, the outputs can also be combined for high current applications, enabling the LT3692 to deliver up to 7A of continuous output current. The combination of the device's 5mm x 5mm QFN-32 package and high switching frequency, which keeps external capacitors and inductor small, provides a very compact, thermally efficient footprint. The LT3692's main switcher utilizes high efficiency 3.8A, 300mVCESAT switches, with the necessary oscillator, control and logic circuitry integrated into a single die. Special design techniques enable high efficiency over a wide input voltage range while its current-mode topology enables fast transient response and excellent loop stability. The LT3692 also offers a frequency divider on one channel which enables it run at frequencies 1/2, 1/4 or 1/8 of the other channel's frequency to enable high step-down ratios while minimizing external component size. Enhanced short circuit protection and die temperature monitor offer additional levels of protection. Other features include thermal shutdown and independent power good flags. Summary of Features: LT3692
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