Simplified Block Diagram
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- +2.6V to +5.5V Input Range
- Output Voltages
- +8V Output at 300mA (3V Input Step-Up
- Switching Regulator)
- +22V Output at 20mA (Positive Charge Pump)
- -7V Output at 20mA (Negative Charge Pump)
- +4V Output at ±150mA (Operational Amplifiers VOUT1 and VOUT2)
- Resistor-Adjustable Switching Regulator and Op-Amp Output Voltages
- Logic-Controlled, High-Voltage Switch with Adjustable Delay
- Greater than 85% Efficiency (Step-Up Switching Regulator)
- Selectable 600kHz/1.2MHz Step-Up Switching Frequency
- Low-Profile Surface-Mount Components
- Also Evaluates the MAX1542 (IC Replacement Required)
- Fully Assembled and Tested
- Car-Navigation Displays
- LCD Monitor Panels
- Notebook Computer Displays
The EV kit operates from a DC supply voltage of +2.6V to +5.5V. The step-up switching regulator is configured for a +8V output providing at least 250mA. The positive charge pump is configured for a +22V output providing at least 20mA. The negative charge pump is configured for a -7V output providing at least 20mA. The two operational amplifiers are both configured for +4V, each capable of providing up to ±150mA peak. The high-voltage switch can be used to delay the startup of the positive charge pump's output. The delay time is set with an external capacitor.
The MAX1543 EV kit demonstrates low quiescent current and high efficiency (85%) for maximum battery life. Operation at 1.2MHz allows the use of tiny surface-mount components. The MAX1543 QFN package (0.8mm maximum height) with low-profile external com-ponents allows this circuit to be less than 1.25mm high.