Ricoh launches a Buck-Boost DC/DC Converter with 300 nA quiescent current for IoT devices and wearables

Feb 25, 2020

Campbell, CA, February 25, 2020 - Ricoh Electronic Devices Co., Ltd. in Japan has launched the RP605 Buck-Boost DC/DC Converter with a unique integrated battery voltage monitor to make it possible to measure the remaining charge left in the battery. It is designed to use in wearable devices, applications for Internet of Things (IoT) and wireless communications modules requiring a low level of current consumption to extend battery life.

The additional battery monitor circuit is one of the key features of the RP605, a conventional way to measure the remaining battery charge is using an external resistor divider + MOSFET connected to an A/D Converter. However, the input impedance of this solution is typically low resulting in a considerable current flow to ground, draining the battery and limiting the lifetime of the application. The RP605 provides a simple solution with a built-in resistor divider and voltage follower as a buffer. As an advantage, this circuit has a much lower current flow to ground and the output is compatible with the input impedance of the A/D converter.  The quiescent current of this circuit is only 100 nA and has an additional chip enable pin (CE2) instead of using a discrete MOSFET. All essential components for this circuit are integrated into the chip, reducing valuable circuit board space and cost. In this way, it is possible to make a simple fuel gauge for primary batteries, for example.

The RP605 is particularly well suited when a supply voltage is required and located somewhere in between the voltage level of a fully charged and fully discharged battery. At a certain moment the DC/DC Converter switches over from Buck to Boost mode automatically in order to maintain the output voltage setting. The RP605 is designed for applications that are mainly in sleep mode and wake-up periodically to perform a measurement, transmit data and then return to sleep mode. For this type of applications, the current consumption in sleep mode should remain as low as possible. The RP605 has an impressive low quiescent current and consumes only 300 nA (DC-DC Converter part), prolonging battery life or makes it possible for the designer to select a smaller sized battery for the application.

The RP605 is able to provide up to 300 mA in Buck mode while in Boost mode the output current is less and related to the input voltage level. Multiple protection circuits are integrated, including an Under-Voltage Lock-Out circuit which disables the DC/DC Converter in case the input voltage drops below a minimum threshold. A soft-start circuit controls the output voltage to ramp-up smoothly and prevents any output overshoot and undershoot during the start-up period. The Lx current limit circuit prevents the peak current through the inductor to exceed a specific maximum current threshold. An output overvoltage protection which turns off both the P-channel and N-channel MOSFETs and thermal protection, shutting down the IC in case the junction temperature increases above 140ºC.

The RP605 has an optional auto-discharge function, which rapidly discharges the output capacitor once the chip is disabled by the CE pin. As for the available packages, one can select from a small sized WLCSP-20-P3 and DFN(PLP)2730-12.

Features RP605:

DC/DC Converter

Input Voltage Range: 1.8 V to 5.5 V

Output Voltage Range: (in 0.1 V step) 1.6 V to 5.2 V

Output Voltage Accuracy: ±1.5%

Output Current: (buck mode) 300 mA

Quiescent Current: (device not switching) Typ. 300 nA

Standby Current: 0.01 µA

PMOS On-Resistance: (Vin = 3.6V, RP604Z) 0.12 Ω

NMOS On-Resistance: (Vin = 3.6V, RP604Z) 0.12 Ω

Protection Circuits: UVLO, OVP, Soft-Start, Lx Peak Current, Thermal

Peak Efficiency: 92%

Auto-Discharge: Function Optional

Output Capacitor: 22 µF

Inductor: 2.2 µH

Battery Monitor

Output Voltage Optional: 1/3 Vin or 1/4 Vin

Supply Current: 0.1 µA

Output Capacitor: 0.1 µF to 0.22 µF

Package RP605Z, RP605K: WLCSP-20-P3, DFN(PLP)2730-12

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About Ricoh Electronic Devices Co., Ltd

Ricoh Electronic Devices Co., Ltd is a leading global provider of semiconductor products, offering a comprehensive portfolio of CMOS Power Management and Real Time Clock ICs that enable engineers to design advanced applications for the consumer, industrial and automotive markets. The company's headquarter is based in Japan, as well as development, sales and manufacturing facilities. Regional sales and support offices are located in North America, Europe, and Asia.

Ricoh has an extensive expertise in small package technology and has a focus on developing products providing features such as low-supply current, high-accuracy, high efficiency and high-reliability.

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| About Ricoh |

Ricoh is empowering digital workplaces using innovative technologies and services enabling individuals to work smarter. For more than 80 years, Ricoh has been driving innovation and is a leading provider of document management solutions, IT services, communication services, commercial and industrial printing, digital cameras, and industrial systems.

Headquartered in Tokyo, Ricoh Group operates in approximately 200 countries and regions. In the financial year ended March 2019, Ricoh Group had worldwide sales of 2,013 billion yen (approx. 18.1 billion USD).

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