ZHCSCK8G May 2014 – October 2017 LP8860-Q1
PRODUCTION DATA.
The PSPWM scheme allows delaying the time when each LED output is active. When the LED outputs are not activated simultaneously, the peak load current from the boost output is greatly decreased. This reduces the ripple seen on the boost output and allows smaller output capacitors. Reduced ripple also reduces the output ceramic capacitor audible ringing. The PSPWM scheme also increases the load frequency seen on boost output up to 4 times, therefore transferring possible audible noise to a frequency above human hearing range. In addition, “optical ripple” through the LCD panel is reduced helping in waterfall noise reduction.
Figure 18 shows the available LED output modes. The number of LED outputs used can be one to four; outputs can be tied together to increase current for one string or all four strings can be independently controlled in the cluster mode.
In <LED_STRING_CONF[2:0]> = 000 the phase difference between channels is 90 degrees. This mode is intended for application in Figure 53. When <LED_STRING_CONF[2:0] > = 001 the phase difference between 3 channels in display mode is 120 degrees. This mode is intended for application shown in Figure 63. When <LED_STRING_CONF[2:0]> = 010 the phase difference between 2 channels in display mode is 180 degrees, channels 3 and 4 in cluster mode, intended for application illustrated by Figure 60. LED strings not used in Display mode can be used for Cluster mode, or not used. When <LED_STRING_CONF[2:0]> = 111 all strings are in cluster mode.
MODE | LED_STRING_CONF[2:0] | DESCRIPTION |
---|---|---|
0 | 000 | 4 separate LED strings with 90° phase shift |
1 | 001 | 3 separate LED strings with 120° phase shift (String 4 in cluster mode or not used) |
2 | 010 | 2 separate LED strings with 180° phase shift (Strings 3 and 4 in cluster mode or not used) |
3 | 011 | 1 LED string. (Strings 2,3 and 4 in cluster mode or not used) |
4 | 100 | 2 LED strings (1+2, 3+4) with 180° phase shift. Strings with same phase can be connected together. |
5 | 101 | 1 LED string (1+2+3+4). All strings with same phase (can be tied together). |
6 | 110 | 1 LED string (1+2). 1st and 2nd strings tied with same phase, strings 3 and 4 are in cluster mode or not used |
7 | 111 | All strings are used in cluster mode with 90° phase shift |
LED_STRING_CONF[2:0] | 000 | 001 | 010 | 011 | 100 | 101 | 110 | 111 | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
SETUP | No. of Displ. Strings | No. of Cluster Strings | No. of Displ. Strings | No. of Cluster Strings | No. of Displ. Strings | No. of Cluster Strings | No. of Displ. Strings | No. of Cluster Strings | No. of Displ. Strings | No. of Cluster Strings | No. of Displ. Strings | No. of Cluster Strings | No. of Displ. Strings | No. of Cluster Strings | No. of Displ. Strings | No. of Cluster Strings |
4 | 0 | 3 | 1 | 2 | 1+1 | 1 | 1+1+1 | 2+2 | 0 | same phase/
4 tied |
0 | same phase/
2 tied |
1+1 | 0 | 1+1+1+1 | |
Adaptive voltage control | Y | Y | N | Y | N | Y | N | Y | Y | Y | N | N | ||||
FAULT DETECTION | ||||||||||||||||
Open LED string | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | ||||
Short LED string | Y | Y | Y | Y | Y | N | Y | Y | Y/N | Y/N | Y | Y | ||||
OPTIONS | ||||||||||||||||
Sloper | Y | Y | N | Y | N | Y | N | Y | Y | Y | N | N | ||||
Dithering | ||||||||||||||||
Int. temp. current dimming | ||||||||||||||||
Ext. temp. current limit | ||||||||||||||||
Ext. temp. current dimming | Y | Y | Y | Y | Y | |||||||||||
Brightness modes | All | All | Reg. only | All | Reg. only | All | Reg. only | All | All | All | Reg. only | Reg. only | ||||
PMW dimming | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | ||||
Hybrid PWM and Current Dimming | N | N | N | N | N | |||||||||||
LED OUTPUT PARAMETERS (PLL Frequency 40 MHz) | ||||||||||||||||
ƒLED PWM min | 4.9 kHz | 4.9 kHz | 4.9 kHz | 4.9 kHz | 4.9 kHz | |||||||||||
Resolution at min ƒLED PWM | 13 | 13 | 13 | 13 | 13 | |||||||||||
fLED PWM max | 39 kHz | 39 kHz | 39 kHz | 39 kHz | 4.9 kHz | |||||||||||
Resolution at max ƒLED PWM | 10 | 10 | 10 | 10 | 13 | |||||||||||
Additional Dither for Display | 4 | 4 | N | 4 | N | 4 | N | 4 | 4 | 4 | N | N | ||||
LED OUTPUT PARAMETERS (PLL Frequency 5 MHz/off | ||||||||||||||||
fLED PWM min | 4.9 kHz | 4.9 kHz | 4.9 kHz | 4.9 kHz | 610 Hz | |||||||||||
Resolution at min ƒLED PWM | 10 | 10 | 10 | 10 | 13 | |||||||||||
ƒLED PWM Max | 39 kHz | 39 kHz | 39 kHz | 39 kHz | 610 Hz | |||||||||||
Resolution at max ƒLED PWM | 7 | 7 | 7 | 13 | ||||||||||||
Additional bits with dither | 4 | 4 | N | 4 | N | 4 | N | 4 | 4 | 4 | N | N |