Power-On Reset and Watchdog Timer Functions / Maximum 150°C Junction Temperature Features

January 13, 2012 – Linear Technology Korea (CEO Hong Sa-gwak) announced the release of the H-grade version of the LT3641, a dual-channel, current-mode step-down switching regulator equipped with power-on reset and watchdog timer functions. This product has an input voltage range of 4V to 42V and features 55V overvoltage protection, making it ideal for load dump and cold crank situations commonly occurring in automotive applications where stable output regulation is required even under high input transient voltage conditions of around 55V.
The LT3641 utilizes a unique dual-channel design approach combining a high-input voltage asynchronous channel providing 1.3A output current and a low-input voltage (2.5VIN ~ 5.5VIN) synchronous channel providing up to 1.1A continuous output current. While this device allows individual inputs for each channel, most applications can provide dual outputs while optimizing efficiency and switching frequency by using the output of the high-voltage channel to power the lower-voltage channel. For example, using a nominal 12V input and 2MHz switching frequency, the LT3641 delivers 3.3V output at 85% efficiency at 600mA through the high-voltage channel and provides 1.8A output at 800mA with 90% secondary conversion efficiency through the low-voltage channel.
The H-grade version operates at temperatures up to 150°C maximum junction temperature compared to E and I grade versions with 125°C maximum junction temperature. All electrical specifications are identical across E, I, and H versions. H-grade devices are tested and guaranteed to operate at maximum junction temperatures of 150°C, making them ideal for automotive and industrial applications that can be easily exposed to high ambient temperatures.
The LT3641HFE is supplied in a 28-pin thermally enhanced TSSOP-28 package at $4.43 per unit based on 1,000 units. This device is currently available for purchase. For more information, refer to www.linear.com/product/LT3641.

Photo Description: High-Temperature Grade 42V (55V Overvoltage Protection) Dual Step-Down Regulator with Power-On Reset and Watchdog Timer Functions

Product Features: LT3641H

• High-Voltage Buck Regulator:
o Operating Range 4V ~ 42V, Overvoltage Protection up to 55V
o 1.3A Output Current
• Low-Voltage Synchronous Buck Regulator:
o 2.5V ~ 5.5V Input Voltage Range
o 1.1A Output Current
• Synchronizable and Adjustable 350kHz ~ 2.5MHz Switching Frequency
• Programmable Power-On Reset Timer
• Programmable Window Mode Watchdog Timer
• Typical Quiescent Current: IQ < 290μA
• Short-Circuit Protection
• Programmable Soft-Start Function
• Low Shutdown Current: IQ < 1μA
• Thermal Shutdown
• Supplied in Thermally Enhanced 28-Pin TSSOP Package
• Maximum Junction Temperature 150°C