Evaluating the LTC7871

Demonstration circuit DC2886A is a high power, high efficiency six-phase bidirectional converter featuring the LTC7871 and LTC7060. The terminals labeled VHIGH and VLOW are either inputs or outputs depending on the direction of power flow. When the switch at SW1 is in the BUCK position, VLOW provides a 14V output and VHIGH is the input with a range of 30V to 70V. When the switch is in the BOOST position, VHIGH provides a 48V output and VLOW is the input with a range of 10V to 14V. The maximum VLOW current is 180A in both directions. The maximum output power is 2.5kW when operating as a buck within the input voltage range. When operating as a boost, the maximum output power is 2.4kW when the input voltage is 14V. External airflow is required when operating at maximum power. The MOSFETs in each phase are driven by the LTC7060 half bridge driver. Each LTC7060 gate driver is placed next to the MOSFETs and receives a PWM signal from the LTC7871.

The inductor current for each phase is sensed with a low 1mΩ sense resistor using a highly accurate AC/DC current sensing architecture with low power dissipation. The LTC7871’s constant-current loop provides a DC current limit for the current flowing in or out of the VLOW terminal depending on the state of the BUCK pin. This current can be programmed with the SETCUR pin and monitored with the IMON pin.

The DC2886A provides a SPI compatible serial port. With a DC2026C (Linduino® One) demo board and QuikEval™ software on a host computer, the user can:

Margin the regulated VLOW or VHIGH up or down. Margin the DC current limit up or down with the SETCUR pin. Adjust the frequency spread and modulation rate of the spread spectrum circuit, when spread spectrum is enabled. Monitor the operational status and faults of the LTC7871.

Additional features of the DC2886A include:

Pin selectable light load operating modes Buck: FCM, pulse-skipping and Burst Mode® Operation Boost: FCM and pulse-skipping SYNC and CLKOUT pins Optional jumper to enable spread spectrum modulation RUN, FAULT, PGOOD and PWNEN pins BUCK pin to externally control the direction of power flow Footprint for an optional heatsink

Hadrware Specifications

Power Supply Requirments

DC2886A can be operated as buck or boost converter. Using buck converter, supply is connected to the Vhigh that could range from 30V to 70V with a typical value of 48V. During boost mode operation, supply is connected to Vlow that can operate form 10V to 14V with a typical value of 12V.

Board Connector and Jumper Settings

The (JP4) jumper toggles Run pin. Connect to ON for normal oepration.

The (SW1) DPDT has two positions: Boost or Buck mode.

Pin Description

Several Pins are exposed on the board

Communication Pins(SDA, CSB, SDO, SCL)
Fault pin
PWMEN pin
PGOOD pin
RUN pin
SYNC adn CLKOUT pin
SETCUR pin
IMON pin

No-OS Build Setup

Please see: https://wiki.analog.com/resources/no-os/build

No-OS Supported Examples

The initialization data used in the examples is taken out from: Project Common Data Path

The macros used in Common Data are defined in platform specific files found in: Project Platform Configuration Path

Basic example

This is a simple example that initializes the LTC7871, reading configuration setup of the board.

In order to build the basic example make sure you are using this command:

make EXAMPLE=basic

IIO example

This project is actually an IIOD demo for DC2886A evaluation board. The project launches a IIOD server on the board so that the user may connect to it via an IIO client.

Using IIO-Oscilloscope, the user can configure the device.

If you are not familiar with ADI IIO Application, please take a look at: IIO No-OS

If you are not familiar with ADI IIO-Oscilloscope Client, please take a look at: IIO Oscilloscope

The No-OS IIO Application together with the No-OS IIO LTC7871 driver take care of all the back-end logic needed to setup the IIO server.

This example initializes the IIO device and calls the IIO app as shown in: IIO Example

In order to build the IIO project make sure you you are using this command:

make EXAMPLE=iio_example

No-OS Supported Platforms

Maxim Platform

Used hardware

Connections:

Function	MAX32690EVKIT Pin	Voltage shifter	DC2886A Pin
SPI Clock (SCK)	P2.29 (SPI0B_SCK)		SCL
SPI Master In Slave Out (MISO)	P2.27 (SPI0B_MISO)	A1
SPI Master In Slave Out (MISO)		B1	SDO*
SPI Chip Select (CS)	P2.26 (SPI0B_SS0)		CSB
SPI Master Out Slave In (MOSI)	P2.28 (SPI0B_MOSI)		SDA
GPIO (PWMEN Pin)	P4.0 (GPIO)		PWMEN
Ground (GND)	GND	GND	GND
3.3V	Vaux	LV
5V		HV	V5

'* - DC2886A SDO's external pull-up resistor should be replaced with 1kohm resistor

Build Command

# to delete current build
make reset
# to build the project for running basic example
make EXAMPLE=basic TARGET=max32690 MXC_SPI_VERSION=v1
# to build the project for running iio example
make EXAMPLE=iio_example TARGET=max32690 MXC_SPI_VERSION=v1
# to flash the code
make run