20V, 4-Channel Configurable Buck DC-DCs Plus Eval Board
The LTC®3376 from Analog Devices is a highly flexible multioutput dc-dc converter IC. The device includes four synchronous buck converters, configured to share eight 1.5A power stages, powered from independent 3V to 20V inputs. The dc-dc converters are assigned to one of fifteen power configurations via pin strappable CFG0 to CFG3 pins.
The LTC3376 is designed for use in telecommunications and industrial 12Vdc distributed power system architectures.
The LTC3376 includes the integration of ceramic capacitors into the package for the BST pins thereby saving PCB space. The common buck switching frequency may be programmed with an external resistor, synchronized to an external oscillator, or set to a default internal 2MHz clock.
The operating mode for all dc-dc converters may be programmmed via the SYNC/MODE pin for Burst Mode or forced continuous mode operation. The PGOOD1 to PGOOD4 outputs indicate when each enabled dc-dc is within a specified percentage of its final output.
Current monitors allow for external monitoring of each buck's load. The EXTVCC pin allows for the internal circuitry to run from a 3V to 5.5V rail for improved efficiency. Precision RUN pin thresholds facilitate power-up sequencing. The LTC3376 is available in a 64 lead 7mm × 7mm BGA (0.8mm ball pitch).
Summary of Features
- Wide VIN Range: 3V to 20V
- Wide VOUT Range: 0.4V to 0.83 x VIN
- Eight 1.5A Buck Power Stages Configurable as 1 to 4 Output Channels
- 15 Unique Pin Selectable Output Configurations (1.5A to 12A per Channel)
- Internal Boost Capacitors for Reduced PCB Space
- No Load IQ 27µA 1 Buck Enabled; 42µA All Bucks Enabled
- 1% VOUT Accuracy on All Channels
- Peak Current Mode Control (Burst Mode® Operation/Forced Continuous)
- Precision RUN Inputs, Individual PGOOD Outputs for Power Sequencing
- 1MHz to 3MHz Frequency (RT Programmable, PLL SYNC, or Internal 2MHz Oscillator)
- TEMP Pin Output Indicates Die Temperature
- Output Current Monitors
- Differential Output Sense
Evaluation Board
Demonstration Circuit DC2966A shows the LTC3376 4-channel configurable buck regulator operating in configuration CFG[3:0] = 0000. This sets the LTC3376 to operate as a quad buck with all four possible outputs, each capable of 3A. By default, outputs 1-4 are set at 5V, 3.3V, 2.5V, and 1.8V, respectively.
Demonstration Circuit DC2966A
Outputs can be enabled, disabled, or sequenced individually. By default, all channel inputs are separate but the board can be configured to power all or some channels from a common input. Each channel has a PGOOD LED indicator to show that its output is regulating within the desired range. Switching operation can allow burst mode for high-efficiency operation at low load currents but can also be forced to continuous pwm for more deterministic EMI.
The PCB is laid out on 6 layers and the demonstration circuit provides access to all features of the LTC3376.
