mx881 Clare, Inc., mx881 Datasheet - Page 5

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

MX881
AC Characteristics
Junction temperature range 0 to + 115°C
Control Register
The MX881 control register is a 5 bit register that allows the user to program the maximum output
voltage and the maximum average battery current during the charge cycle. Table1 shows how the bits in
the control register are assigned. ABC(2:0) are used to set the average battery current and OVS(1:0) are
used to set the output voltage selection reference.
Table 1 – Control Register
Output Voltage Selection
The MX881 limits the high voltage placed on the external capacitor by comparing a divided down version
of the secondary flyback voltage to an internal voltage. This internal voltage is programmable to 4
discrete values to allow the user to change the flash energy. The external voltage divider ratio needed to
obtain 330V maximum output voltage should be 269 to 1. This external resistor divider network is also
used to form a low pass filter with an internal capacitor so it is important that the equivalent resistance of
the voltage divider network be 3K ohms. Table 2 shows the internal reference values used for possible
values of the capacitor charge voltage. The default value is 11.
Table 2 - Output Voltage Selection
MX881
Drawing No. 088109
Symbol
T
T
T
T
T
T
START
END
IGBT-ON
IGBT-OFF
LED-ON
LED-OFF
BIT:
Control:
OVS Value (Binary)
Parameter
CHARGE High to Beginning of
Charge Cycle
CHARGE Low to End of Charge
Cycle
FLASH High to IGBTGATE High
FLASH Low to IGBTGATE Low
LED_EN High to Iout > 90mA
LED_EN Low to Iout < 1mA
11
10
01
00
D4
OVS1
Reference Voltage (V
D3
OVS0
1.23
1.19
1.15
1.12
Condition
CL = 6.8nF, 10% to
90%
CL = 6.8nF, 90% to
10%
D2
ABC2
5
TRIP
)
D1
ABC1
Capacitor Voltage
330
320
310
300
D0
ABC0
Min
TBD
TBD
Typ
110
100
100
100
IXYS
www.claremicronix.com
Max
Unit
µS
nS
nS
nS
µS
µS
7/30/07