diff options
| author | Vincent Palatin <vpalatin@chromium.org> | 2014-06-18 10:10:12 -0700 |
|---|---|---|
| committer | chrome-internal-fetch <chrome-internal-fetch@google.com> | 2014-06-20 18:27:16 +0000 |
| commit | 1a4bf7fdaa58d7e05d33bc1faf3fceed8b6ad07a (patch) | |
| tree | 05e39bb69e2974b4936b0fbebbbee677655fe41e | |
| parent | 246053495b3663202d34dd1b0b70302c295b32df (diff) | |
| download | chrome-ec-1a4bf7fdaa58d7e05d33bc1faf3fceed8b6ad07a.tar.gz | |
zinger: update current and voltage sensing gains
On the P2 boards, the operational amplifier gain for current sensing is
exactly x100 rather than x101.
(non-inverter configuration with R1=1.8kOhm R2=178kOhm)
The voltage gain constant had a typo introducing a 10% error.
the voltage divider is 10k/100k,so it's x11 gain.
ie it should be written (10+100)/10 rather than (10+110).
Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
BRANCH=none
BUG=chrome-os-partner:28331
TEST=make BOARD=zinger
checked manually with a voltmeter and traces.
Change-Id: I8097ab50149fee319efc11ebae75802e8a49a7f8
Reviewed-on: https://chromium-review.googlesource.com/204540
Reviewed-by: Alec Berg <alecaberg@chromium.org>
Commit-Queue: Vincent Palatin <vpalatin@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>
| -rw-r--r-- | board/zinger/usb_pd_policy.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/board/zinger/usb_pd_policy.c b/board/zinger/usb_pd_policy.c index 83737b717b..ee03ec7ccc 100644 --- a/board/zinger/usb_pd_policy.c +++ b/board/zinger/usb_pd_policy.c @@ -75,9 +75,9 @@ static timestamp_t fault_deadline; /* Current sense resistor : 5 milliOhm */ #define R_SENSE 5 /* VBUS voltage is measured through 10k / 100k voltage divider = /11 */ -#define VOLT_DIV ((10+110)/10) -/* The current sensing op-amp has a x101 gain */ -#define CURR_GAIN 101 +#define VOLT_DIV ((10+100)/10) +/* The current sensing op-amp has a x100 gain */ +#define CURR_GAIN 100 /* convert VBUS voltage in raw ADC value */ #define VBUS_MV(mv) ((mv)*ADC_SCALE/VOLT_DIV/VDDA_MV) /* convert VBUS current in raw ADC value */ |