L99LDLH32 datasheet(17/142 Pages) STMICROELECTRONICS

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DS12879 Rev 6

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L99LDLH32

Linear current sources

141

Linear current sources

4.1

General description

The L99LDLH32 features 32 high side linear current generators to regulate from 1 mA up to

15 mA current on the output channels.

The output channels can be put in parallel to address higher current than the programmable

one and, for each channel, the current can be individually programmed by using an

integrated 8-bit DAC. The output channels paralleling is allowed, provided that all these

channels are controlled simultaneously. Moreover, in case of fault on one of the paralleled

channels, it is recommended to deactivate all the channels belonging to the same fault bus

(by setting FAULT_REACT_MODE bit to "0", see Table 8).

Supplied directly from car battery, the L99LDLH32 IC guarantees up to 35 V output driving

capability - suitable to cover the OLED forward voltage wide spread.

Each O/LED string can be supplied by battery or through one pre-regulator connected

between battery and linear current regulators.

The pre-regulated (VPRE_REG) and battery (VS) voltages are internally monitored by an 8-bit

ADC, the results are stored in a dedicated result register. The ADC is used also to monitor

the device temperature (TJ) as well as all the output channels. These channels are

refreshed once per PWM period in on-state.

The minimum PWM on-time (vs PWM frequency) - to ensure a correct channel ADC reading

- is tPWM_ON_OFF time (see Table 77). In any case, ADC will not perform any reading

operation before a configurable blanking time (tDIAG_BLANK, see Table 79) has elapsed. This

blanking time is applied on the first channel turn on as well as on each PWM rising edge.

The ADC monitoring of all these parameters allows a complete diagnostic: open load

detection, hard short circuit (versus ground), O/LED current derating in case of device

temperature increasing.

The L99LDLH32 features an 8-bit logarithmic PWM for dimming control to adjust

separately the brightness for each channel. A linear 8-bit global dimming dedicated for each

function group mapped with Direct Input pin can be superimposed with the channel

individual dimming.

A slow turn-on and turn-off time (tSR_ON and tSR_OFF) of the channel improves the system

low noise generation performances.

Moreover, this device features the output gradual delay (tGD) which avoids contemporary

turning on of all the channels used for a specific light function, reducing the inrush current.

To further improve EMI performances, the device implements an internal clock dithering:

more precisely, a triangular waveform (see the Figure 57) is applied to the embedded 20

MHz oscillator to have a spread spectrum noise reduction. Frequency modulation and

deviation, along with rejection, are showed in the Table 39, for each of the eight possible

configurations the user can set by means of 3 dedicated bits (DITHERING [2÷0], see

FTP/RAM memory map, Chapter 7).

The L99LDLH32 integrates a thermal sensor block used to sense the device junction

temperature (TJ) as well as to detect thermal warning (TW) and thermal shutdown (TSD)

thresholds, granting device protection in case of temperature increasing.

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