mx881 Clare, Inc., mx881 Datasheet - Page 6

• Manufacturer Part Number: mx881
• Description: Enon Flash Controller & Led Torch Driver
• Manufacturer: Clare, Inc.

MX881
Average Battery Current
The 3 bits (ABC2 – ABC0) of the control register are used to program the maximum average battery
current during a charge cycle. The MX881 does this by limiting the minimum off time during a switching
cycle. The off time compensates for variation of the battery voltage so that the average current is
independent of battery voltage. The default value of ABC is 101. With the default value of ABC, the
average battery current control circuits are disabled for maximum efficiency, and the maximum battery
current is approximately 220mA. The average current versus the output voltage is shown in Figure1.
The battery current peak value is preset internally to 0.7A. This current must be averaged by placing an
external bypass capacitor from VCC to ground. A 10uF capacitor is recommended for good current
smoothing and averaging.
Figure 1 - Average Battery Current
MX881
Drawing No. 088109
60
50
40
30
20
10
0
0
Average Battery Current Setting of 50mA (ABC = 000)
100
200
V
6
300
400
VCC = 3.0V
VCC = 5.5V
IXYS
www.claremicronix.com
7/30/07