■ DESCRIPTION

The MB3887 is a DC/DC converter IC suitable for down-conversion, using pulse-width (PWM) charging and enabling output voltage to be set to any desired level from one cell to four cells. These ICs can dynamically control the secondary battery’s charge current by detecting a voltage drop in an AC adapter in order to keep its power constant (dynamically-controlled charging) . The charging method enables quick charging, for example, with the AC adapter during operation of a notebook PC. The MB3887 provides a broad power supply voltage range and low standby current as well as high efficiency, making it ideal for use as a built-in charging device in products such as notebook PC. This product is covered by US Patent Number 6,147,477.

■ FEATURES

• Detecting a voltage drop in the AC adapter and dynamically controlling the charge current

(Dynamically-controlled charging)

• Output voltage setting using external resistor : 1 cell to 4 cells

• High efficiency : 96% (VIN = 19 V, Vo = 16.8 V)

• Wide range of operating supply voltages : 8 V to 25 V

• Output voltage setting accuracy : 4.2 V ± 0.74% (Ta = −10 °C to +85 °C , per cell)

• Charging current accuracy : ±5%

• Built-in frequency setting capacitor enables frequency setting using external resistor only

• Oscillation frequency range : 100 kHz to 500 kHz

• Built-in current detection amplifier with wide in-phase input voltage range : 0 V to VCC

• In standby mode, leave output voltage setting resistor open to prevent inefficient current loss

• Built-in standby current function : 0 µA (standard)

• Built-in soft-start function independent of loads

• Built-in totem-pole output stage supporting P-channel MOS FET devices

• One type of package (SSOP-24pin : 1 type)

■ Application

• Notebook PC