Microchip Technology MCP73855, Руководство пользователя

Страница: 12 / 20

MCP73855 Evaluation Board User’s Guide
DS51522A-page 8

2004 Microchip Technology Inc.
FIGURE 2-1: Setup Configuration Diagram.
2.3 DETAILED DESCRIPTION
The MCP73855 Evaluation Board is set-up to evaluate simple, stand-alone, linear
charging of single-cell Li-Ion/Li-Polymer battery packs. The reference design provides
constant current charging followed by constant voltage charging with automatic charge
termination. As provided, the MCP73855 Evaluation Board is set for fast charge
constant current levels of 85 mA with J4 (PROG) open and 400 mA with J4 (PROG)
connected to J3 (V
IN
–). The MCP73855 is provided in a 3 mm X 3 mm, 10-lead DFN
package and is equipped with shutdown control, status indicator and safety timer. Refer
to the MCP73853/55 data sheet (DS21915) for details on individual device features.
2.3.1 Input Source
The MCP73855 Evaluation Board is designed to provide a fast charge current up to
400 mA, typically. The input source should provide a voltage in the range of 4.5V to
5.5V. The input source should be capable of providing a minimum of 2.5W.
Charge currents between 85 mA and 400 mA can be obtained by adjusting the value
of the charge programming resistors (R
2
) and connecting surface-mount test point J4
(PROG) to J3 (V
IN
–). Refer to the MCP73853/55 data sheet (DS21915) for details on
determining the appropriate programming resistor.
2.3.2 Safety Timer Periods
The MCP73855 Evaluation Board can be used with a variety of battery packs. As
provided, the MCP73855 Evaluation Board is set up to perform well with single-cell,
100 mAh to 500 mAh battery packs. Battery packs with alternative capacities and
various charge currents can be implemented. The safety timer periods may need to be
adjusted in order to ensure a full charge. The safety timer periods can be adjusted by
changing the capacitance of C
3
. Refer to the MCP73853/55 data sheet (DS21915) for
details on determining the appropriate timer capacitance.
2.3.3 Disable Control
The MCP73855 Evaluation Board is designed to provide stand-alone operation. The
installed MCP73855 device is enabled whenever the input source is present. To
disable charging, a jumper can be placed between J1 (EN) and J3 (V
IN
–).
Regulated
Wall Cube
+
–
Single
Lithium-Ion
Cell