LP8860-Q1_17 Datasheet, PDF (33/110 Pages) Texas Instruments – Low-EMI Automotive LED Driver With Four 150-mA Channels

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LP8860-Q1
SNVSA21F – MAY 2014 – REVISED JULY 2017
The <DISP_CL1_CURRENT[11:0]> register is initialized during start-up by the <LED_CURRENT_CTRL[11:0]>
EEPROM bits. <DRV_LED_CURRENT_SCALE[2:0]> are initialized by the <DRV_LED_CURRENT_SCALE[2:0]>
EEPROM bits. Cluster mode current registers for outputs OUT2 and OUT3 are initialized by 0 during power on
reset.
Current register value must be not written to 0 if brightness is not zero – it may cause LED faults and adaptive
voltage control instability.
8.3.5 Cluster Mode
Cluster is a simplified mode which allows independent current and PWM control for every string in cluster mode.
In this mode brightness control is limited to conventional PWM through the SPI/I²C brightness registers. The
PWM input pin, Hybrid PWM and Current dimming mode, slope control, or dither are not available. Brightness for
different LED strings depends on <DISP_CL1_BRT[15:0]>, <CL2_BRT[12:0]>, <CL3_BRT[12:0]> and
<CL4_BRT[12:0]> registers. If OUT1 is in cluster mode, only 13 MSB are used. If all LED outputs are in the
cluster mode, LED output PWM resolution is always 13 bits, and frequency depends on
<PWM_RESOLUTION[1:0]> bits (see Table 13). If one or more of the LED outputs is in display mode, frequency,
and resolution for strings in the cluster mode is the same as for strings in the display mode (see Table 1).
CL#_CURRENT[7:0]
CL#_BRT[12:0]
Cluster
Current
Register
Cluster
Brightness
Register
PWM
Comparator
...
PWM_RESOLUTION[1:0]
PWM_FREQ[3:0]
PWM
Counter
CLUSTER
MODE LED
CURRENT
SINKS
PLL Clock 5...40 MHz
Copyright © 2016, Texas Instruments Incorporated
Figure 20. Cluster Mode Block Diagram
Table 13. Output PWM Frequency for Mode 7 (All Strings in Cluster Mode)
PWM_RESOLUTION[1:0]
00
OSC frequency (MHz)
5
ƒ_{LED PWM} (Hz)
610
01
10
1221
10
20
2442
11
40
4883
When the LP8860-Q1 is set in cluster mode, fault protection functionality is limited. Headroom for LED strings
must be between the high-voltage comparator level <DRV_LED_FAULT_THR[1:0]> and low-voltage comparator
level <DRV_HEADR[2:0]> (which depend upon saturation voltage); otherwise a fault is generated.
Adaptive boost control does not follow strings in cluster mode. Display mode strings and cluster mode strings
must not be connected to the same boost. When LED strings in display and cluster modes are connected to the
same boost, LED open or short faults may be generated if the LED forward-voltage mismatch is too high.
If all LED outputs are in cluster mode, boost output voltage is fixed and must be set by EEPROM
<BOOST_INITIAL_VOLTAGE[5:0]> bits to a value high enough to ensure correct LED string operation in all
conditions.
<EN_CL_LED_FAULT>=0 disables cluster LED fault detection, even if all LED strings are in the cluster mode.
The current de-rating (based on the internal temperature sensor) and LED current limitation (based on external
temperature sensor) are not functional in this mode, and analog current dimming based on the external sensor
functionality is limited (LED shutdown for high temperature is not operational).
Copyright © 2014–2017, Texas Instruments Incorporated
Product Folder Links: LP8860-Q1
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