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authorWerner Almesberger <werner@almesberger.net>2016-12-07 10:20:24 -0300
committerWerner Almesberger <werner@almesberger.net>2016-12-07 10:20:24 -0300
commite8afd93afc9d434ddb69d73611e6829c20f610c7 (patch)
treee498d5e599fa244ee0e67a08e9cbf6fc6d0ab4b6 /ir
parent96a9112ad1fe224ac8ac7974210a6c63572eacb6 (diff)
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ir/leddrv.fig, ir.tex: add TX slew rate control
Diffstat (limited to 'ir')
-rw-r--r--ir/ir.tex6
-rw-r--r--ir/leddrv.fig12
2 files changed, 15 insertions, 3 deletions
diff --git a/ir/ir.tex b/ir/ir.tex
index 3749fac..9fe7776 100644
--- a/ir/ir.tex
+++ b/ir/ir.tex
@@ -192,6 +192,7 @@ without parity format.} \\
% - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
\subsection{Combined characteristics}
+\label{combined}
Combining the specifications from the preceding sections, we obtain the
following common characteristics for transmitter and receiver:
@@ -765,6 +766,11 @@ voltage $\rm V_F=\FPrnd{2}{Vf}~V$, the voltage drop across the FET is
$\rm V_{DS}=V_{BAT}-V_F-I_{LED}\cdot R2=\FPrnd{2}{Vds}~V$, and the
power dissipation $\rm \FPrnd{0}{Vds * Iled * 1000}~mW$.
+Resistor R3 acts with the FET gate capacitance as low-pass filter to
+control the slew rate. Using $\rm C_{ISS}\approx 15~pF$ at
+$\rm V_{DS}\approx 4 V$, we get a cut-off frequency of about 1~MHz
+with $\rm R=10~kOhm$.
+
% -----------------------------------------------------------------------------
\section{Receiver circuit}
diff --git a/ir/leddrv.fig b/ir/leddrv.fig
index d8de5d6..bdbad57 100644
--- a/ir/leddrv.fig
+++ b/ir/leddrv.fig
@@ -1,8 +1,8 @@
-#FIG 3.2 Produced by xfig version 3.2.5c
+#FIG 3.2 Produced by xfig version 3.2.6
Landscape
Center
Metric
-A4
+A4
100.00
Single
-2
@@ -44,6 +44,10 @@ Single
5625 7335 5625 8100
2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
5625 8550 5625 9000
+2 2 0 2 0 7 50 -1 -1 0.000 0 0 -1 0 0 5
+ 4725 7245 5175 7245 5175 7425 4725 7425 4725 7245
+2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+ 4725 7335 4275 7335
4 1 0 50 -1 22 12 0.0000 4 135 360 6525 5580 Vbat\001
4 0 0 50 -1 22 12 0.0000 4 135 195 6660 7245 T1\001
4 0 0 50 -1 22 12 0.0000 4 135 990 6660 7470 DMN26D0UT\001
@@ -51,9 +55,11 @@ Single
4 0 0 50 -1 22 12 0.0000 4 135 1035 6795 6525 VSMB2948SL\001
4 0 0 50 -1 22 12 0.0000 4 135 210 6705 8280 R2\001
4 0 0 50 -1 22 12 0.0000 4 135 225 6705 8460 4.7\001
-4 2 0 50 -1 22 12 0.0000 4 165 885 5130 7380 IR_TX_LED\001
4 0 0 50 -1 22 12 0.0000 4 135 210 5805 8280 R1\001
4 0 0 50 -1 22 12 0.0000 4 135 225 5805 8460 1M\001
4 0 0 50 -1 18 8 0.0000 4 105 105 6255 7065 D\001
4 0 0 50 -1 18 8 0.0000 4 105 90 6255 7695 S\001
4 2 0 50 -1 18 8 0.0000 4 105 105 6075 7290 G\001
+4 2 0 50 -1 22 12 0.0000 4 165 885 4230 7380 IR_TX_LED\001
+4 1 0 50 -1 22 12 0.0000 4 135 210 4950 7200 R3\001
+4 1 0 50 -1 22 12 0.0000 4 135 270 4950 7605 10k\001