Analog Devices has released the Power by Linear™ LTC3372, a highly integrated power management solution for systems that require multiple low voltage outputs generated from an input voltage as high as 60V. The LTC3372 features a 60V synchronous buck switching regulator controller followed by four configurable synchronous monolithic buck regulators. This combination provides up to five high efficiency low quiescent current outputs in a single IC, ideal for automotive, industrial and medical applications.

The LTC3372's buck controller operates over a 4.5V to 60V input voltage range and drives an all N-channel MOSFET power stage. Its output can be programmed to either 3.3V or 5V and can generate an output current up to 20A. The controller output is typically used to feed the four monolithic buck regulators. Each monolithic buck channel can be programmed to regulate an output voltage as low as 0.8V with a configurable output current up to 4A. Eight 1A integrated power stages are programmed by the C1-C3 pins into one of eight unique configurations, from a quad 2A buck to a dual 4A buck. This allows only one inductor per channel.

Application Circuit

The LTC3372 offers a low IQ solution ideal for battery-powered or automotive applications in which one or more power supply rails are always on. With just the high voltage controller enabled, the device draws 15µA from a 12V input supply while regulating the output to 5V at no load. Each monolithic buck regulator adds only 8µA of additional IQ per channel enabled. The LTC3372's monolithic buck switching frequency can be programmed from 1MHz to 3MHz and can be synchronized to an external clock while the buck controller switches at 1/6 of this frequency. Additional features include foldback current limiting, soft-start, short-circuit protection and output overvoltage protection.

The LTC3372 is available in a thermally enhanced 48-pin 7mm × 7mm QFN package. E and I grades are specified over an operating junction temperature range of –40°C to 125°C, and the H grade features operation from –40°C to 150°C.

LTC3372 Key Features

• High Voltage Buck Controller: VIN = 4.5V to 60V, VOUT = 5V/3.3V
• Low Voltage Buck Regulators: VINA-H = 2.25V to 5.5V, VOUT1-4 ≥ 0.8V
• 8 X1A LV Buck Integrated Power Stages, Configurable as 2, 3 or 4 Output Channels
• 8 Unique Output Configurations (1A to 4A per Channel)
• Low Total No-Load Input Supply Current (IQ)
  • 15μA HV Controller Only (5VOUT)
  • 23μA HV Controller Only (3.3VOUT)
  • 9μA Per Additional LV Regulator Channel
• 1MHz to 3MHz Operation (HV Controller Runs at 1/6 Frequency)
• Programmable Frequency or Synchronizable to External Clock
• Programmable Watchdog & Power-On Reset Delay
• IC Die Temperature Monitor Output
• Thermally Enhanced 48-Pin7mm × 7mm QFN Package

The LTC3372 is supported by the DC2419A demonstration board, the board features the LTC3372 in a multi-output step-down converter. The controller portion of the LTC3372 drives a high output voltage (HV) buck converter which has an input voltage range of 6V to 60V. Its output voltage (VOUT_HV) is nominally 5V but can be configured for either 5V or 3.3V with the VOUTPRG pin. VOUT_HV supplies power to the configurable buck regulator. This regulator provides four low voltage (LV) outputs labelled VOUT1-4. These outputs are 1.2V/2A, 1.8V/2A, 2.5V/2A and 3.3V/2A respectively. When VOUT_HV is configured for 5V, it can supply 6A to the external loads with full load on VOUT1-4. With no load on VOUT1-4, VOUT_HV can supply 10A to the external loads

The LV buck regulator consists of eight power stages that can be arranged in up to four channels. The LV regulator on the DC2419A is setup for four channels of two power stages each. With modifications, the LV buck regulator can be setup for eight different configurations. If VOUT_HV is programmed for 3.3V, then VOUT4 which provides 3.3V/2A will be in dropout. This rail will require an external input voltage to stay in regulation. The LV rails operate at 2MHz and the HV converter operates at one-sixth this frequency or 333kHz.

The high frequency of the LV rails allows the use of 4mm × 4mm inductors. The power stage for the HV converter consists of 60V avalanche rated MOSFETs and a 2.2μH 10mm × 10mm inductor. A 4mΩ discrete sense resistor is used to sense current.

The low IQ current of the LTC3372 provides high efficiency at light loads. When the VOUT_HV is supplying the nominal 5V, its Burst Mode® efficiency with 1mA load is 90.3% for a 12V input. When the HV converter is off, it only draws 27μA from a 12V input.

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Click here to download datasheet for the LTC3372

Click here to download the manual for the DC2419A Demonstration Board

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