ZHCSCK8H May 2014 – April 2025 LP8860-Q1
PRODUCTION DATA
Figure 6-9 shows the PWM calculation data flow for display mode. In PWM direct control mode most of the blocks are bypassed, and this flow chart does not apply.
Figure 6-9 PWM Data Flow Calculation| BLOCK NAME | DESCRIPTION |
|---|---|
| PWM detector | PWM detector block measures the duty cycle of the input PWM signal. Resolution depends on the input signal frequency. Hysteresis selection sets the minimum allowable change to the input. Smaller changes are ignored. |
| Brightness register | 16-bit register for brightness setting <DISP_CL1_BRT[15:0]> |
| Brightness mode control | Brightness control block gets 16-bit value from the PWM detector, and also 16-bit value from the brightness register <DISP_CL1_BRT[15:0]>. <BRT_MODE[1:0]> selects whether to use PWM input duty cycle value, the brightness register value or multiplication. |
| Temperature regulator | Temperature regulator reduces LED PWM duty cycle depending on internal and external temperature sensor. See Section 6.3.9.2 and Section 6.3.9.3 for details |
| External temperature sensor | External NTC temperature sensor |
| Internal temperature sensor | Internal die temperature sensor |
| Sloper | Sloper makes the smooth transition from one brightness value to another. Slope time can be adjusted from 0 ms to 511 ms with <PWM_SLOPE[2:0]> EEPROM bits. |
| Advanced sloper | Advanced slope makes brightness changes smoother for eye; see Section 6.3.2.5 for details |
| PWM and Current Control | Hybrid PWM and Current dimming improves the optical efficiency of the LEDs by using PWM control with lower brightness values and current control with greater values. <EN_PWM_I> EEPROM bit enables Hybrid PWM and Current control. PWM dimming range can be set 12.5 to 50% of the brightness range with <GAIN_CTRL[2:0]> EEPROM bits. Current slope can be adjusted by using the <I_SLOPE[2:0]> EEPROM bits. See Section 6.3.2.6 for details |
| Dither | With dithering the output resolution can be further increased. This way the brightness change steps are not visible to eye. The amount of dithering is 0 to 4 bits, and is selected with <DITHER[2:0]> EEPROM bits. |
| PWM comparator | PWM comparator compares the PWM counter output to the value received from the dither block. Output of the PWM comparator directly controls the LED current sinks. If Phase Shift PWM (PSPWM) mode is used, the PWM counter values for each LED output are modified by summing an offset value to create different phases. |
| PWM counter | Overflowing 16-bit PWM counter creates new PWM cycle. Step for incrementation is defined by <PWM_FREQ[3:0]> and <PWM_RESOLUTION[1:0]> bits, see Table 6-3. |