Simplified Block Diagram
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- +1.8V to +5.5V Input Range
- Output Voltages
- +8V Output at 250mA (2.2V 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)
- 1.2MHz Step-Up Switching Frequency
- Selectable 600kHz Step-Up Switching Frequency (Component Changes Required)
- Low-Profile Surface-Mount Components (1.25mm max)
- Fully Assembled and Tested
- Automotive Displays
- LCD Monitor Panels
- Notebook Computer Displays
The EV kit operates from a DC supply voltage of +1.8V to +5.5V. The step-up switching regulator is configured for a +8V output providing at least 250mA from a 2.2V input. 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 output of the positive charge pump's startup. The delay time is set with an external capacitor, C6.
The MAX8739 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 MAX8739 TQFN package (0.8mm maximum height) with low-profile external components allows this circuit to be less than 1.25mm high.