IC-HT datasheet(17/45 Pages) ICHAUS

17 / 45 page

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iC-HT

DUAL CW LASER DIODE DRIVER

Rev B1, Page 17/45

ACC (Automatic Current 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

EACC2

Addr. 0x15; bit 0

R/W 0

APC mode enabled for channel 2

ACC mode enabled for channel 2

Table 23: APC/ACC in channel 2

In ACC mode the internal programmable logarithmic

monitor resistor (PLR) is not used. Instead the inter-

nal RACCx resistor is used to set the current. 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 26. Figure 8 shows an

example of this conﬁguration.

Two different current ranges can be set through reg-

ister bit RACCx, with RACCx = 1 for up to 75 mA and

with RACCx = 0 for up to 650 mA. The programmable

overcurrent shutdown protects against over regula-

tions during the laser power-on. Table 44 shows some

typical current settings. For detailed limits, please refer

to Electrical Characteristics No. 114

ACC typical current settings

REFx

RACCx=0 RACCx=1

0x000

77.0 mA

9.06 mA

0x001

77.2 mA

9.08 mA

0x010

77.4 mA

9.10 mA

...

0x200

256.2 mA

30.14 mA

0x201

256.8 mA

30.21 mA

0x202

257.4 mA

30.28 mA

...

0x3FD

846.0 mA

99.53 mA

0x3FE

848.0 mA

99.77 mA

0x3FF

850.0 mA

100 mA

Table 24: ACC typical current settings

ACC

APC

RACC

PLR1

..10 nF..

255

8 Bit

LASER CHANNEL 1

10 Bit

8 Bit

10 Bit

I LDK

CI1

MRL1

MDA1

AGND1

CIL1

CI1

LDK1

DCO

ECIE1

VDD

LDK1

ADSNF1

OVC

DISP1

EMC

I LDK

CI1

Figure 8: ACC mode simpliﬁed

RACC1

Addr. 0x1A; bit 0

R/W 0

Current range high for channel 1

Current range low for channel 1

Table 25: RACC1 conﬁguration

RACC2

Addr. 0x1A; bit 4

R/W 0

Current range high for channel 2

Current range low for channel 2

Table 26: RACC2 conﬁguration

In each range, the particular overcurrent threshold

value can be set in register ILIMx. The regulator does

differ the two current ranges in ACC.

ILIM1

Addr. 0x11; bit 7:0

R/W 0xFF

0x0A

Channel 1 overcurrent threshold set to minimum

current

. . .

Channel 1 overcurrent threshold set to

Ilim = (∆I(LDK ) · n), n from 10 to 255

0xFF

Channel 1 overcurrent threshold set to maximum

current

Table 27: Overcurrent threshold conﬁguration channel

ILIM2

Addr. 0x16; bit 7:0

R/W 0xFF

0x0A

Channel 2 overcurrent threshold set to minimum

current

. . .

Channel 2 overcurrent threshold set to

Ilim = (∆I(LDK ) · n), n from 10 to 255

0xFF

Channel 2 overcurrent threshold set to maximum

current

Table 28: Overcurrent threshold conﬁguration channel

An overcurrent event can be simulated using bit

SOVCx. If SOVCx = 1, the corresponding overcurrent

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