introduction
Today's industrial electronic systems contain many of the same components as consumer electronics, such as microcontrollers, FPGAs, system-on-chip ASICs, and other electronics, requiring multiple low-voltage rails under a variety of different load current conditions. In addition, industrial applications require a button interface, a power supply that remains on for a real-time clock (RTC) or memory, and the ability to derive input power from a high-voltage power supply. Other required features may include a watchdog timer (WDT), a global stop or reset button, software-adjustable voltage levels, and low-input/output voltage and high-chip temperature error reporting.
The LTC3375 is a highly configurable multi-output step-down power converter with the features typically required for industrial electronics and the flexibility to configure a wide range of outputs from 1A to 4A.
Configurable maximum output current
The eight 1A channels of the LTC3375 can be combined to produce various combinations of 1A, 2A, 3A, and 4A buck regulators, such as the 15 different output current configurations listed in Table 1.
Connecting the feedback pin of a given channel to its VIN pin configures the channel as a slave channel to an adjacent channel. Connect the switch pins of the two channels together to share a single inductor and output capacitor. The master/slave channel is enabled with the enable pin of the main regulator and is regulated to the feedback network of the main regulator.
The output current can be increased to 3A or 4A by connecting more adjacent channels. The circuit in Figure 1 shows the LTC3375 configured with a 3A output, a 1A output, two 2A outputs, and an LDO that is always on. The figure also shows how to connect the LTC3375 to control the startup of an upstream external buck controller through the on-chip button interface to provide input power to the LTC3375 buck regulator.
Table 1: LTC3375 Maximum Current Configuration
Figure 1 has a low voltage power supply that can be controlled by a button to control the upstream HV buck converter and the LDO that is always on.
External VCC LDO and external input power start control
The LTC3375 can control an external LDO transmission device to provide its VCC supply and power any other low current electronic components (eg, an RTC). VCC is responsible for powering the internal button circuit, WDT, internal registers, and open-drain resistors. The external LDO in Figure 1 can generate a 3.3V supply from a 24V rail.
When the button is pressed, the ON pin is released and the RUN pin on the LTC3891 is pulled high, providing input power to the LTC3375's buck converter. When the LTC3891 is regulated, the PGOOD pin is released, enabling EN1 of the LTC3375 and turning on the 2A regulator. The remaining regulators can be enabled using an enable pin with a precision threshold or via a software controlled I2C command. Pressing the button again for 10 seconds or longer, or pulling /KILL low for 50ms or longer will cause the ON pin to be pulled low, deactivating all buck stabilization Pressure device.
Unique power control and features
The I2C interface provides a large number of regulator operation controls. Each regulator can be set to perform a high efficiency Burst Mode operation to conserve power under light load conditions or a forced continuous mode to achieve a lower output ripple voltage. In addition, each regulator can shift the switching cycle phase by 0°, 90°, 180°, or 270° (relative to the reference clock) to provide a lower input pattern when multiple outputs are powered by large loads. Wave current. Another feature is the ability to control the rise or fall of each output voltage by adjusting the feedback reference voltage (adjusted from the default 725mV setpoint, stepped at 25mV, adjustable from 425mV to 800mV). In addition, the I2C interface is used to report the error condition of each regulator.
The LTC3375 has a reset (/RST) pin and an interrupt request (/IRQ) pin that can be programmed to report when the output voltage of any regulator drops below 92.5% of the regulation point. The /IRQ pin can also be set to report when the input voltage drops below the undervoltage lockout (UVLO) threshold or the die temperature reaches the set temperature threshold. The regulator's PGOOD and UVLO states, chip temperature alarms, and measured chip temperature can be monitored by the microprocessor through the I2C interface.
One problem with microprocessors is that software errors can cause a program to abort. The LTC3375 has a Watchdog Timer Input (WDI) pin that monitors the SCL pin or some other pin to determine if the software is still running. If the software has stopped running, the Watchdog Timer Output (WDO) pin can be used to reset the microprocessor or to power off the high voltage (HV) buck converter and the LTC3375 buck regulator. When the WDT condition is not met, connecting the WDO pin to the /RST pin of the microprocessor will cause the microprocessor to reset. Connecting the WDO pin to the /KILL pin will cause the ON pin to go low, deactivating the HV buck converter and all LTC3375 regulators. As a last resort, the /KILL pin can be pulled low with a push button "paper clip" switch to de-energize all regulators.
in conclusion
The LTC3375 can be configured to have multiple stable 1A to 4A outputs (up to 8A total) and has many of the features required in today's industrial electronics.
—— This article is selected from the electronic enthusiast website September special issue “Intelligent Industry Special Issueâ€, please indicate the source, please do it!
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