IC-HTP datasheet(18/51 Pages) ICHAUS

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iC-HTP

DUAL CW P-TYPE LASER DIODE DRIVER

Rev B1, Page 18/51

ACC Current Ranges

CRNGx(1:0) RACCx

Idc(LDA)

750 mA

100 mA

90 mA

25 mA

12 mA

9 mA

3 mA

1.1 mA

Table 28: ACC current ranges

For fine-tuning the regulated current, the reference volt-

age can be set with a 10 bit logarithmic D/A converter,

which is configurable through the register REFx. This

converter has a voltage range that goes typically from

0.1 V to 1.1 V, allowing an operation resolution of typi-

cally 0.235%. More information on the logarithmic D/A

converter can be found on page 29.

A programmable overcurrent threshold is available in

order to protect the laser diode during the power-on

instant. The overcurrent protection value, Ilim, must be

configured in the 8 bit register ILIMx using the following

equations:

Ilim = (∆I(LDA), max) · n · k

n =

Ilim

k · ∆I(LDA), max

with n from 0 to 255.

If ILIM is set to 0 in ACC mode, the overcurrent protec-

tion is disconnected.

∆

I(LDA), max is the shutdown current threshold reso-

lution (maximum value) (cf. Electrical Characteristics

No. 108). Its value depend on the current range de-

fined by register bit RACCx. If RACCx = 1, the over-

current threshold is in the low range and ∆I(LDA), max

= 0.375 mA. If RACCx = 0, the overcurrent threshold

is in the high range and ∆I(LDA), max = 3 mA. k is

a current range factor, with a value depending on

CRNGx(1:0) register

ILIM1

Addr. 0x11; bit 7:0

R/W 0xFF

0x00

Channel 1 overcurrent threshold set to the minimum

current in APC mode (EACC1 = 0) or overcurrent

protection disabled in ACC mode (EACC1 = 1)

. . .

Channel 1 overcurrent threshold set to

Ilim = (∆I(LDA), max · n · k), n from 0 to 255

0xFF

Channel 1 overcurrent threshold set to the maximum

current

Table 29: Overcurrent threshold configuration

channel 1

ILIM2

Addr. 0x16; bit 7:0

R/W 0xFF

0x00

Channel 2 overcurrent threshold set to the minimum

current in APC mode (EACC2 = 0) or overcurrent

protection disabled in ACC mode (EACC2 = 1)

. . .

Channel 2 overcurrent threshold set to

Ilim = (∆I(LDA), max · n · k), n from 0 to 255

0xFF

Channel 2 overcurrent threshold set to the maximum

current

Table 30: Overcurrent threshold configuration

channel 2

An overcurrent event can be simulated using bit SOVCx.

If SOVCx = 1, the corresponding overcurrent error bit

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

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 31: 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 32: Simulate overcurrent channel 2

Calculating the expected output current in ACC

mode

The following formula can be used to estimate the ex-

pected current value for an ACC configuration. The

resulting value is a typical value.

Ilaser(typ) = Vrefx

Rsensex · MFACTx

Where

Vrefx = Vref0(1 +

∆

Vref (%)

100

)n+1, n from 0 to 1023

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