POWER AND LINEAR IC SOLUTIONS

Power ICs Thrive in Caustic Automotive Environment

Linear Technology switching regulators can operate through cold crank and load dump conditions yet require less than 100µA quiescent current (see table 1). For example, LT3480 is a 2A, 38V step-down switching regulator protected from input transients up to 60V. In no-load standby, burst mode operation keeps quiescent current under 70µA.

Linear Technology’s LT3480 switching regulator is ideal for automotive load dump and cold crank conditions with its 3.6V to 38V input voltage range and 60V transient protection. The LT3480 will regulate a 3.3V output during a 36V transient caused by load dump. Above 41.5V, the LT3480 shuts itself down to protect itself and downstream circuitry and restarts regulation when the transient drops below 38V.

Load dump is a failure condition when battery cables disconnect during alternator charging; abrupt disconnection can produce transient voltage spikes as high as 60V, risking damage to the DC/DC converters downstream of the alternator. Cold crank occurs when extremely low temperatures have caused engine oil to become viscous, therefore requiring extra torque from the starter motor and drawing more battery current for ignition, pulling the battery/primary bus voltage temporarily below 4.0V. Some applications, such as engine control, safety and navigation systems, require consistent output voltage (usually 3.3V) to operate.



The LT3480’s 3A internal switch can deliver up to 2A of continuous output current to voltages as low as 0.79V yet it requires minimal externals and can deliver efficiencies as high as 90%. The LT3480’s burst mode operation maintains quiescent current to only 70µA, well suited for automotive or telecom system applications that demand always-on operation and optimum battery life.

Switching frequency is user programmable from 200kHz to 2.4MHz enabling designers to optimise efficiency while avoiding critical noise-sensitive frequency bands. The small 3mm x 3mm DFN-10 package (or thermally enhanced MSOP-10E) and its high switching frequency keeps external inductors and capacitors small, providing a very compact, thermally efficient footprint.

Product Information

Part No.	Device Architecture	VIN Range	IOUT (A)	Frequency	IQ	Package
LT3437	Step-Down Regulator	3.3V to 80V	0.40	200kHz	100µA	DFN-10
LT3433	Buck-Boost Regulator	4V to 60V	0.40	200kHZ	100µA	TSSOP-16E
LT1976/7	Step-Down Regulator	3.3V to 60V	1.25	200/500kHZ	100µA	TSSOP-16E
LT3480	Step-Down Regulator	3.6V to 38V, 60V max	2.00	200kHz to 2.4MHz	70µA	3x3 DFN-10, MSOP-10E
LT3481	Step-Down Regulator	3.6V to 34V, 36V max	2.00	300kHz to 2.8MHz	50µA	3x3 DFN-10, MSOP-10E
LT3681	Step-Down Regulator	3.6V to 34V, 36V max	2.00	300kHz to 2.8MHz	50µA	3x4 DFN-14
LT3434/5	Step-Down Regulator	3.3V to 60V	2.50	200/500kHZ	100µA	TSSOP-16E
LT3680	Step-Down Regulator	3.6V to 36V	3.50	200kHz to 2.4MHz	75µA	3x3 DFN-10, MSOP-10E

Features

• High efficiency 3A, 0.25Ω switch, boost diode, oscillator, control + logic circuitry in a single die.
• Low ripple burst mode operation
  • High efficiency at low output currents: output ripple below 15mV_PK-_PK
• Current mode topology enables fast transient response and excellent loop stability
• External synchronization (from 250kHz to 2MHz)
• Power good flag
• Soft-start capability

Applications

• Automotive switching regulators
  • Engine control, safety and navigation system
  • Cold crank and load dump start condition
• Telecom portable systems

For further information, including the Linear Technology LT3480 Datasheet, please click here