IC-HTP datasheet(30/51 Pages) ICHAUS

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iC-HTP

DUAL CW P-TYPE LASER DIODE DRIVER

Rev B1, Page 30/51

10 BIT LINEAR A/D CONVERTER

A 10 bit linear A/D converter is available for each chan-

nel when working in MCU mode. A variety of voltages

can be measured by the converter with two resolutions:

• V(LDAx) up to 11 V with 11.81 mV resolution

• V(VDD) up to 8 V with 8.6 mV resolution

• V(VB) up to 11 V with 11.81 mV resolution

• V(VBLx) up to 11 V with 11.81 mV resolution

• V(MDKx) up to 1.1 V with 1.075 mV resolution

• V(RACC) up to 1.1 V with 1.075 mV resolution

• V(PLRx) up to 1.1 V with 1.075 mV resolution

The register bits ADCCx select the signal measured

with the 10 bit A/D converter.

ADCC1(2:0)

Addr. 0x10; bit 7:5

R/W 000

0xx

Channel 1 ADC disabled

100

Channel 1 ADC sourced by V(MDK1), ADFNS1 = 1,

CMES1 = 0

100

Channel 1 ADC sourced by V(PLR1), ADFNS1 = 0,

CMES1 = 0

100

Channel 1 ADC sourced by ACC current sensor,

CMES1 = 1

101

Channel 1 ADC sourced by V(VB)

110

Channel 1 ADC sourced by V(VBL1)

111

Channel 1 ADC sourced by V(LDA1)

Table 63: ADC channel 1 source selection

ADCC2(2:0)

Addr. 0x15; bit 7:5

R/W 000

0xx

Channel 2 ADC disabled

100

Channel 2 ADC sourced by V(MDK2), ADFNS2 = 1,

CMES2 = 0

100

Channel 2 ADC sourced by V(PLR2), ADFNS2 = 0,

CMES2 = 0

100

Channel 2 ADC sourced by ACC current sensor,

CMES2 = 1

101

Channel 2 ADC sourced by V(VDD)

110

Channel 2 ADC sourced by V(VBL2)

111

Channel 2 ADC sourced by V(LDA2)

Table 64: ADC channel 2 source selection

With ADCCx(2:0) = 100, the signal to the A/D converter

is selected by register bit ADFNSx (A/D converter force

not sense). With ADFNSx = 0 the measuring point to the

A/D converter is the internal sense node of the internal

programmable logarithmic monitor resistor (PLR). With

ADFNSx = 1 the sensing point is connected directly to

MDKx pin.

ADFNS1

Addr. 0x1A; bit 2

R/W 0

ADC measurement PLR1 after level shifting (sense)

ADC measurement MDK1 pad (force)

Table 65: ADC channel 1 force/sense selection

ADFNS2

Addr. 0x1A; bit 6

R/W 0

ADC measurement PLR2 after level shifting (sense)

ADC measurement MDK2 pad (force)

Table 66: ADC channel 2 force/sense selection

With the CMESx bit, the ADC can be used for laser

current measurement in ACC mode. For this measure-

ment, ADCCx register must be set to 100. As shown in

figure 7, a fraction of the current delivered by the driver

to the laser is mirrored to a resistor. The voltage drop

at this resistor is sourced to the ADC. For a given value

of the ADC, the current can be calculated as follows

I(LDAx) =

VFS

1023 ∗ADCx

∗

MFACT

VFS is the fullscale voltage of the A/D converter (cf.

Electrical Characteristics No. 706) typical 1.1 V. MFACT

is the Mirror factor between the LDA driver and the mea-

surement. This Factor is dependent on the selected

current range (CRNG(1:0)), see table below:

ACC mirror factor

MERGE

CRNGx

Mirror factor

Mirror Factor set to 2500

Mirror Factor set to 333

Mirror Factor set to 83

Mirror Factor set to 30

Mirror Factor set to 5000

Mirror Factor set to 666

Mirror Factor set to 166

Mirror Factor set to 60

Table 67: Mirror factor

R is the value of the measurement resistance, this value

is dependent on RACC bit, see table below:

RACC1

Addr. 0x1A; bit 0

R/W 0

Current range high for channel 1, Current sensor

resistor (Rsensex) set to 2kΩ

Current range low for channel 1, Current sensor

resistor (Rsensex) set to 16kΩ

Table 68: Current range configuration channel 1

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