MX881

IXYS

AC Characteristics

Junction temperature range 0 to + 115

°C

Symbol

Parameter

Condition

Min

Typ

Max

Unit

CHARGE High to Beginning of

Charge Cycle

110

µS

CHARGE Low to End of Charge

Cycle

100

nS

FLASH High to IGBTGATE High

CL = 6.8nF, 10% to

90%

100

nS

FLASH Low to IGBTGATE Low

CL = 6.8nF, 90% to

10%

100

nS

LED_EN High to Iout > 90mA

TBD

µS

LED_EN Low to Iout < 1mA

TBD

µS

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

BIT:

D4

D3

D2

D1

D0

Control:

OVS1

OVS0

ABC2

ABC1

ABC0

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

OVS Value (Binary)

Capacitor Voltage

11

1.23

330

10

1.19

320

01

1.15

310

00

1.12

300

MX881

5

7/30/07

Drawing No. 088109

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