SNVSC74A September 2023 – July 2024 LP5813
PRODUCTION DATA
The LP5813 integrates ghosting elimination circuits to avoid both upside and downside ghosting phenomenon. The ghosting elimination can be disabled by setting clamp_dis = 1h, which is default as 0 and enabling the function.
Voltage on the outputs is clamped during PWM off time in the rest of switching period, or during blank time period, which is set in 'clamp_sel' bit in Dev_Config12 register. Figure 6-12 and Figure 6-13 show the effect of different clamp selection.
A middle voltage Vmid between VOUT and VOUT - Vf is used to clamp the OUTx (x = 0, 1, 2, 3), where Vf is the forward voltage of LED. This scheme can achieve both pre-discharge for scan switch FET and pre-charge for current sinks, which eliminate up-side and down-side ghosting issues in time-multiplexing topology. Since the clamp voltage for scan switch FET and current sinks is the same value, the reverse voltage on LED during deghosting is avoided. There are 4 options for Vmid which is selected in 'vmid_sel' bits in Dev_Config12 register, which can be used for different forward voltage range of different type LEDs.