TI TPS60125PWP

The TPS6012x step-up, regulated charge pumps generate a 3.3-V or 3-V ±4% output voltage from a 1.8-V to 3.6-V input voltage (two alkaline, NiCd, or NiMH batteries). They can deliver an output current of at least 200 mA (100 mA for the TPS60122 and TPS60123), all from a 2-V input. Four external capacitors are needed to build a complete high efficiency dc/dc charge pump converter. To achieve the high efficiency over a wide input voltage range, the charge pump automatically selects between a 1.5× or doubler conversion mode. From a 2-V input, all ICs can start with full load current.

The devices feature the power-saving pulse-skip mode to extend battery life at light loads. TPS60120, TPS60122, and TPS60124 include a low battery comparator. TPS60121, TPS60123, and TPS60125 feature a power-good output. The logic shutdown function reduces the supply current to a maximum of 1 μA and disconnects the load from the input. Special current-control circuitry prevents excessive current from being drawn from the battery during start-up. This dc/dc converter requires no inductors, therefore EMI is of low concern. It is available in the small, thermally enhanced 20-pin PowerPAD package (PWP).

The TPS6012x charge pumps provide a regulated 3.3-V or 3-V output from a 1.8-V to 3.6-V input. They are designed for a maximum load current of at least 200 mA or 100 mA, respectively. Designed specifically for space-critical, battery-powered applications, the complete charge pump circuit requires only four external capacitors. The circuit is optimized for efficiency over a wide input voltage range.

The TPS6012x charge pumps consist of an oscillator, a 1.21-V bandgap reference, an internal resistive feedback circuit, an error amplifier, high current MOSFET switches, a shutdown/start-up circuit, a low-battery or power-good comparator, and a control circuit.

The device consists of two single-ended charge pumps. The power stages of the charge pump are automatically configured to amplify the input voltage with a conversion factor of 1.5 or 2. The conversion ratio depends on input voltage and output current. With input voltages lower than approximately 2.4 V, the convertor will run in a voltage doubler mode with a gain of two. With a higher input voltage, the converter operates with a gain of 1.5. This assures high efficiency over the wide input voltage range of a two-cell battery stack.

The ON-resistance of the MOSFETs that are in the charge path of the flying capacitors is regulated when the charge pump operates in voltage doubler-mode. It is changed depending on the output voltage that is fed back into the control loop. This way, the time-constant during the charging phase can be modified and increased versus a time-constant for fully switched-on MOSFETs. The ON-resistance of both switches and the capacitance of the flying capacitor define the time constant. The MOSFET switches in the discharge path of the charge pump are always fully switched on to their minimum rDS(on). With the time-constant during charge phase being larger than the time constant in discharge phase, the voltage on the flying capacitors stabilizes to the lowest possible value necessary to get a stable V₀.

The voltage on the flying capacitors is measured and compared with the supply voltage (V₁). If the voltage across the flying capacitors is smaller than half of the supply voltage, then the charge pump switches into the 1.5× conversion-mode. The charge pump switches back from a 1.5× conversion-mode to a voltage doubler mode if the load current in 1.5× conversion-mode can no longer be delivered.

With this control mode the device runs in doubler-mode at low V₁ and in 1.5× conversion-mode at high V₁ to optimize the efficiency.

• High Average Efficiency Over Input Voltage Range Because of Special Switching Topology
• Minimum 200-mA Output Current From an Input Voltage Range of 1.8-V to 3.6-V
• Regulated 3.3-V or 3-V ±4% Output Voltage
• No Inductors Required, Low EMI
• Only Four External Components Required
• 55-μA Quiescent Supply Current
• 0.05-μA Shutdown Current
• Load Disconnected in Shutdown
• Integrated Low Battery and Power Good Detectors
• Evaluation Module Available (TPS60120EVM-142)

• Applications Powered by Two Battery Cells
• Portable Instruments
• Battery-Powered Microprocessor Systems
• Miniature Equipment Backup-Battery Boost Converters
• PDAs, Organizers, Laptops
• MP-3 Portable Audio Players
• Handheld Instrumentation
• Medical Instruments (e.g., Glucose Meters)
• Cordless Phones