It has been found that the default pulse-skipping mode of the LTC3676 regulators produces noise that the IMX6 is especially susceptible to when run in ldo-bypass mode.
Switch to continuous PWM mode to provide a cleaner rail, as well as 1MHz switching frequency for EMI reduction. There is no noticeable drop in efficiency between pulse-skipping mode and PWM mode in the Ventana IMX6 use case.
Signed-off-by: Tim Harvey tharvey@gateworks.com --- board/gateworks/gw_ventana/common.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/board/gateworks/gw_ventana/common.c b/board/gateworks/gw_ventana/common.c index 366ea93..02e27c7 100644 --- a/board/gateworks/gw_ventana/common.c +++ b/board/gateworks/gw_ventana/common.c @@ -902,6 +902,12 @@ void setup_pmic(void) pmic_reg_read(p, LTC3676_DVB3B, ®); reg |= LTC3676_PGOOD_MASK; pmic_reg_write(p, LTC3676_DVB3B, reg); + + /* Use continuous PWM mode, 1Mhz on all regulators */ + power_ltc3676_swconfig(p, SW1, PWM, PHASE1, F1125KHZ); + power_ltc3676_swconfig(p, SW2, PWM, PHASE1, F1125KHZ); + power_ltc3676_swconfig(p, SW3, PWM, PHASE1, F1125KHZ); + power_ltc3676_swconfig(p, SW4, PWM, PHASE1, F1125KHZ); } } }