IC-HT datasheet(15/42 Pages) ICHAUS

15 / 42 page

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iC-HT

DUAL CW LASER DIODE DRIVER

Rev A1, Page 15/42

Imon(min) =

Vref (0x 000,max )

Rmda(RMDx =0xFF ,min)

= 0.11

350000

= 0.31 uA

It is not recommended to conﬁgure iC-HT to have such

small Imon values, otherwise the leakage current at

MDAx may have an inﬂuence (cf. Electrical Charac-

teristics No. 204), especially at high temperatures. To

avoid this, Imon should be much greater than the leak-

age current.

For

calculating

the

maximum

value

Imon,

Vref(0x3FF, min value) (cf. Electrical Characteristics

No. 303) and Rmda(RMDx = 0x00, max vaule) (cf.

Electrical Characteristics No. 201) are used. Since

only the 4 MSB from PLR can be accessed at pin

MDAx, the following formula needs to be used for cal-

culating Rmda(RMDx = 0x00, max value):

Rmd = Rmd0(1 +

∆

Rmd (%)

100

)n+1, n from 0 to 255

Rmda(RMDx = 0x 00, max ) = Rmd0(1 +

∆

Rmd (%)

100

)16

286 = Rmd0(1 +

3.3

100 )

Rmd0 = 170Ω

Therefore:

Imon(max ) =

Vref (0x 3FF ,min)

Rmd0

= 1.00

170

= 5.88 mA

Any other Imon value can be calculated using Rmd for-

mula above. Due to its logarithmic characteristic, the

steps between two consecutive values is kept within

3.3 % typical value.

The programmable overcurrent shutdown can be set

to protect the laser by disabling the channel.

The

overcurrent threshold is conﬁgurable in two different

ranges.

The range is selected through register bit

RACCx. If RACCx = 1, the overcurrent threshold is

in the low range, up to 90 mA. If RACCx = 0, the over-

current threshold is in the high range, up to 750 mA (cf.

Electrical Characteristics No. 107 ).

RACC1

Addr. 0x1A; bit 0

R/W 0

Current range high for channel 1

Current range low for channel 1

Table 16: RACC1 current range conﬁguration channel

RACC2

Addr. 0x1A; bit 4

R/W 0

Current range high for channel 2

Current range low for channel 2

Table 17: RACC2 current range conﬁguration channel

In each range, the particular overcurrent threshold

value can be set in register ILIMx.

ILIM1

Addr. 0x11; bit 7:0

R/W 0xFF

0x00

Channel 1 overcurrent threshold set to minimum

current

. . .

Channel 1 overcurrent threshold set to

Ilim = (∆I(LDK ) · n), n from 0 to 255

0xFF

Channel 1 overcurrent threshold set to maximum

current

Table 18: Overcurrent threshold conﬁguration channel

ILIM2

Addr. 0x16; bit 7:0

R/W 0xFF

0x00

Channel 2 overcurrent threshold set to minimum

current

. . .

Channel 2 overcurrent threshold set to

Ilim = (∆I(LDK ) · n), n from 0 to 255

0xFF

Channel 2 overcurrent threshold set to maximum

current

Table 19: Overcurrent threshold conﬁguration channel

An overcurrent event can be simulated using SOVCx.

If SOVCx = 1, the corresponding overcurrent error bit

OVCx will be set to 1, the error will be signaled at

NCHK and the corresponding laser channel will be dis-

abled. The overcurrent error will remain forced until

SOVCx = 0.

SOVC1

Addr. 0x1D; bit 5

R/W 0

No Overcurrent event at channel 1 is simulated.

Overcurrent event at channel 1 simulated.

Table 20: Simulate overcurrent channel 1

SOVC2

Addr. 0x1D; bit 6

R/W 0

No overcurrent event at channel 2 is simulated.

Overcurrent event at channel 2 simulated.

Table 21: Simulate overcurrent channel 2

ACC control mode

In this mode, the laser diode current is controlled and

no monitor diode is required. ACC mode is selected

setting EACCx register bit to 1.

EACC1

Addr. 0x10; bit 0

R/W 0

APC mode enabled for channel 1

ACC mode enabled for channel 1

Table 22: APC/ACC in channel 1

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