UC3845BD1G

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UC3845BD1G Application Field and Working Principles

The UC3845BD1G is a current-mode PWM switching controller that is suitable for a wide range of DC-DC switching power supplies. It is designed to provide good line and load regulation, constant on-time control, high peak current capability, frequency jittering, and other features important to power conversion applications.

This device belongs to PMIC – Voltage Regulators – DC DC Switching Controllers. It is used in applications such as telecom base stations and DC battery-powered systems. The UC3845BD1G offers constant on-time control (COT) with advanced hysterisis curve programming capabilities. It also provides overcurrent protection, thermal shutdown, and various dynamic performance features that make it an ideal choice for a wide range of DC-DC converter applications.

Overview of features:

• Wide supply voltage range (4.5V to 20V)
• High accuracy of current-mode control
• Frequency jittering for EMI reduction
• Adaptive on-time control
• Overcurrent protection
• Thermal shutdown protection
• Enable and power-good output
• Available in 8-pin SOIC and micro-SOIC packages

Application field:

The UC3845BD1G is suitable for a wide range of DC-DC switching power supplies, such as telecom base stations and DC battery-powered systems. Its wide supply voltage range, high accuracy of current-mode control, frequency jittering for EMI reduction, adaptive on-time control, overcurrent protection, thermal shutdown protection, enable and power-good output make it an ideal choice for DC-DC converter applications.

Working Principles:

At the heart of the UC3845BD1G’s optimization is the current mode control. This component has an internal current comparator to sense the amplitude of the output inductor current. A reference frequency, easily set with external resistors, is compared with the inductor current ramp frequency. When the ramp frequency exceeds the reference, the UC3845BD1G turns-off the output switch. This technique provides good line and load regulation and control of output voltage/current even under varying input voltages.

The UC3845BD1G features jittering of its PWM switching frequency inherently. It also provides under-voltage lockout (UVLO), overcurrent protection (OCP), and thermal shutdown. The OCP signal is applied to the EN/UVLO pin to gate the chip output. The UC3845BD1G features an adaptive on-time control and a power-good signal output, which reduces noise and improves power efficiency.

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