ZHCSCK8G May 2014 – October 2017 LP8860-Q1
PRODUCTION DATA.
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).
PWM_RESOLUTION[1:0] | 00 | 01 | 10 | 11 |
---|---|---|---|---|
OSC frequency (MHz) | 5 | 10 | 20 | 40 |
ƒLED PWM (Hz) | 610 | 1221 | 2442 | 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).