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 <thar...@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);
}
}
}
--
1.9.1
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