Automotive 3V to 36V, 3.5A, Low EMI Synchronous Step-Down ConverterMarch 12, 2020 by Paul Shepard
The LM61435-Q1 from Texas Instruments is an automotive-focused, high-performance, dc-dc synchronous step-down converter. With integrated high-side and low-side MOSFETs, up to 3.5A of output current is delivered over a wide input range of 3.0V to 36V; tolerant of 42V, easing input surge protection design. The LM61435-Q1 implements soft recovery from dropout eliminating overshoot on the output.
The LM61435-Q1 is specifically designed for minimal EMI. The device incorporates pseudo-random spread spectrum, adjustable SW node rise time, low-EMI VQFN-HR package featuring low switch node ringing, and optimized pinout for ease of use. The switching frequency can be set or synchronized between 200kHz and 2MHz to avoid noise sensitive frequency bands.
In addition, the frequency can be selected for improved efficiency at low operating frequency or smaller solution size at high operating frequency.
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Auto-mode enables frequency foldback when operating at light loads, allowing an unloaded current consumption of only 7µA (typical) and high light load efficiency. Seamless transition between PWM and PFM modes, along with very low MOSFET ON resistances and an external bias input, ensures exceptional efficiency across the entire load range.
Electrical characteristics are specified over a junction temperature range of -40°C to +150°C.
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Summary of Features
- AEC-Q100 qualified for automotive applications
- Temperature grade 1: -40°C to +150°C, TJ
- Functional safety capable
- Documentation available to aid functional safety system design
- Optimized for ultra low EMI requirements
- Hotrod™ package minimizes switch node ringing
- Parallel input path minimizes parasitic inductance
- Spread spectrum reduces peak emissions
- Adjustable SW node rise time
- Designed for automotive applications
- Supports 42 V automotive load dump
- ±1% total output regulation accuracy
- VOUT adjustable from 1 V to 95% of VIN
- 3-V dropout with 3-A load (typical)
- High efficiency power conversion at all loads
- 7-µA no load current at 13.5 VIN, 3.3 VOUT
- 91% PFM efficiency at 1-mA, 13.5 VIN, 5 VOUT
- External bias option for improved efficiency
- Suitable for scalable power supplies