Add power information to hardware pages.

Squash from v0.0.12-maintenance:

Power information additions.

Expanded the section "Powering the Maple", added a new "Power Regulation on the Maple" section.

Power info updated for MN and Mini

RET6 power info update

Fixed broken link.

Had wrong link to datasheet for MCP1703.

maple-native-beta: 80-column cosmetic fix

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>

4 files changed, 167 insertions, 48 deletions

diff --git a/source/hardware/maple-mini.rst b/source/hardware/maple-mini.rst
index 986ab4b..58e394d 100644
--- a/source/hardware/maple-mini.rst
+++ b/source/hardware/maple-mini.rst
@@ -50,9 +50,40 @@ directly.
 
 .. warning:: The silkscreen on the Maple Mini suggests it will accept
    an input voltage up to 16 V.  We recommend applying **no greater
-   than 12 V**.
-
-   See :ref:`this erratum <maple-mini-vin>` for more information.
+   than 12 V**, and potentially even lower depending upon the current
+   draw requirements of the application. Please see :ref:`Power
+   Regulation on the Maple Mini <maple-mini-power-regulation>` for
+   more information.
+
+.. _maple-mini-power-regulation:
+
+Power Regulation on the Maple Mini
+----------------------------------
+
+Power regulation on the Maple is provided by two low dropout linear
+voltage regulators. (The part is the MCP1703 from Microchip, in the
+SOT-23A package. You can download the datasheet `here
+<http://ww1.microchip.com/downloads/en/DeviceDoc/22049a.pdf>`_ ). One
+of the regulators supplies power to the digital voltage plane; the
+other supplies power to the analog voltage plane.
+
+These voltage regulators nominally take an input of up to 16V. In
+addition, while the maximum continuous output current for the board is
+250mA, if you are powering the board off higher voltages the amount
+off current it can supply goes down, due to the regulators needing to
+dissipate the extra power. So if you are powering the board off 12V,
+the max current is about 40mA at room temperature. In general (again,
+at room temperature) the max power dissipation (PD) for the chip is
+about .37W, and output current = PD/(Vin-Vout). For exact max current
+calculations, please refer to the datasheet linked above.
+
+If you are planning to draw a lot of current from the Maple board, it
+is necessary to provide input power as close to 3.3V as
+possible. Powering the microcontroller circuitry and LEDs on the board
+alone takes approximately 30mA, so if you are powering the board with
+12V that leaves only 10mA (at best) available for powering any user
+circuitry. Attempting to draw more than 10mA runs the risk of shorting
+out the power regulators and bricking your board.
 
 .. _maple-mini-gpios:
 
@@ -339,14 +370,12 @@ This section lists known issues and warnings for the Maple Mini Rev 2
 .. _maple-mini-vin:
 
 * **Silkscreen Vin voltage mistake**: The silkscreen on the Maple Mini
-  falsely indicates that Vin may be supplied with up to 16 V.  We
-  recommend an input voltage **no greater than 12 V**.
-
-  The voltage regulator on the Mini is rated up to 16 V.  However, our
-  tests indicate that as its input voltage approaches 16 V, its output
-  begins to rise to levels higher than those recommended by ST for
-  supplying the STM32F103CB.  The limit of 12 V keeps the voltage
-  supplied to the processor at safe levels.
+  falsely indicates that Vin may be supplied with up to 16V.  We
+  recommend an input voltage **no greater than 12V**, and potentially
+  even lower depending upon the current draw requirements of the
+  application. Please see :ref:`Power Regulation on the Maple Mini
+  <maple-mini-power-regulation>` for more information.
+
 
 Recommended Reading
 -------------------
diff --git a/source/hardware/maple-native-beta.rst b/source/hardware/maple-native-beta.rst
index f120c05..f1b2284 100644
--- a/source/hardware/maple-native-beta.rst
+++ b/source/hardware/maple-native-beta.rst
@@ -46,20 +46,57 @@ Technical Specifications
 Powering the Maple Native
 -------------------------
 
-The Maple Native may be powered from the barrel jack connector, USB,
-or a LiPo battery.  The power source is determined by the header
-labeled "PWRSEL" on the silkscreen.  Boards are shipped with a jumper
-on the USB selector.  In order to power it off of an alternative
-source, unplug the Maple Native, then move the jumper to the desired
-selector before reconnecting power.
-
-You can also power the Maple Native via the pin labeled "Vin" on the
-vertical header to the right of the PWRSEL header.  This pin feeds
-into both the digital and analog voltage regulators.  However, don't
-do this while simultaneously powering the board from another source,
-or you could damage it.
-
-We recommend an input voltage no greater than 12 V.
+The power source is determined by the header labeled "PWRSEL" on the
+silkscreen. The Maple Native may be powered from USB (marked "USB" on
+the PWRSEL header), a LiPo battery (marked "BAT"), or one of the two
+"Vin" pins (marked "EXT").  Boards are shipped with a jumper on the
+USB selector.  In order to power it off of an alternative source,
+unplug the Maple Native, then move the jumper to the desired selector
+before reconnecting power.
+
+The "Vin" line is available on the pin labeled "Vin" on the vertical
+header to the right of the PWRSEL header, as well as on the
+unpopulated two-pin connector on the upper left corner of the
+board. On this latter connector, polarity was accidentally left
+unmarked: the leftmost, round pin should be power, while the square
+pin should be ground.
+
+When powering the Maple Native board from a battery or the Vin lines,
+care must be taken not to over-voltage the board. In general, an upper
+limit of 12V input is acceptable, but this may vary depending upon the
+current draw requirements of the application. Please see :ref:`Power
+Regulation on the Maple Native <maple-native-b-power-regulation>` for
+more information.
+
+.. _maple-native-b-power-regulation:
+
+Power Regulation on the Maple Native
+------------------------------------
+
+Power regulation on the Maple Native is provided by two low dropout
+linear voltage regulators. (The part is the MCP1703 from Microchip, in
+the SOT-23A package. You can download the datasheet `here
+<http://ww1.microchip.com/downloads/en/DeviceDoc/22049a.pdf>`_). One
+of the regulators supplies power to the digital voltage plane; the
+other supplies power to the analog voltage plane.
+
+These voltage regulators nominally take an input of up to 16V. In
+addition, while the maximum continuous output current for the board is
+250mA, if you are powering the board off higher voltages the amount
+off current it can supply goes down, due to the regulators needing to
+dissipate the extra power. So if you are powering the board off 12V,
+the max current is about 40mA at room temperature. In general (again,
+at room temperature) the max power dissipation (PD) for the chip is
+about .37W, and output current = PD/(Vin-Vout). For exact max current
+calculations, please refer to the datasheet linked above.
+
+If you are planning to draw a lot of current from the Maple Native
+board, it is necessary to provide input power as close to 3.3V as
+possible. Powering the microcontroller circuitry and LEDs on the board
+alone takes approximately 30mA, so if you are powering the board with
+12V that leaves only 10mA (at best) available for powering any user
+circuitry. Attempting to draw more than 10mA runs the risk of shorting
+out the power regulators and bricking your board.
 
 Using the Built-in Battery Charger
 ----------------------------------
diff --git a/source/hardware/maple-ret6.rst b/source/hardware/maple-ret6.rst
index d5bf049..21c033b 100644
--- a/source/hardware/maple-ret6.rst
+++ b/source/hardware/maple-ret6.rst
@@ -58,9 +58,20 @@ standard Maple <maple-powering>`.
 
 .. warning:: The RET6 Edition silkscreen falsely indicates that the
    barrel jack accepts up to 18 V.  We recommend a barrel jack input
-   voltage **no greater than 12 V**.
+   voltage **no greater than 12V**, and potentially even lower
+   depending upon the current draw requirements of the
+   application. The same goes for powering off LiPo batteries.
 
-   See :ref:`this erratum <maple-barrel-jack>` for more information.
+   Please see :ref:`Power Regulation on the Maple
+   <maple-power-regulation>` for more information.
+
+.. _maple-ret6power-regulation:
+
+Power Regulation on the Maple RET6
+----------------------------------
+
+Power regulation on the Maple RET6 works in the :ref:`same way as the
+standard Maple <maple-power-regulation>`.
 
 Using the Built-in Battery Charger
 ----------------------------------
@@ -373,11 +384,17 @@ features only available on the STM32F103RET6.
 
 .. _maple-ret6-barrel-jack:
 
-* **Barrel jack power supply voltage mistake**: The silkscreen next to
-  the barrel jack connector incorrectly indicates that up to an 18 V
-  input voltage is allowed.  **We do not recommend exceeding 12 V**.
-
-  See this :ref:`Maple erratum <maple-barrel-jack>` for more
+* **Barrel jack power supply voltage mistake**: The acceptable voltage
+  range given next to the barrel jack on the Maple RET6 is
+  **incorrect**.  The given range is 7V — 18V.  In fact, **18V is too
+  high** and should not be supplied to your board. The original
+  voltage regulators used on the Maple were rated up to 18V.  However,
+  the voltage regulators on current Maple Revs are rated up to only
+  16V, and due to the current draw requirements of the board, operate
+  properly only up to 12V.  The recommended maximum voltage you should
+  apply is **12V**, and potentially even lower depending upon the
+  current draw requirements of the application. Please see :ref:`Power
+  Regulation on the Maple <maple-power-regulation>` for more
   information.
 
 * **Power supply marketing mistake**: We originally sold the Maple
diff --git a/source/hardware/maple.rst b/source/hardware/maple.rst
index 610fdfc..aff64d5 100644
--- a/source/hardware/maple.rst
+++ b/source/hardware/maple.rst
@@ -103,15 +103,50 @@ header.  This pin feeds into both the digital and analog voltage
 regulators.  However, don't do this while simultaneously powering the
 board from another source, or you could damage it.
 
+When powering the board from a barrel jack, **double check the
+polarity of the barrel.** The appropriate polarity is noted on the
+silkscreen right next to the connector.
+
 .. warning:: Silkscreens on Maples up through Rev 5s manufactured in
    Spring 2011 falsely indicated that the barrel jack could be
-   supplied by up to 18 V.  We recommend a barrel jack input voltage
-   **no greater than 12 V**.
-
-   Rev5s manufactured after Spring 2011 may still have this error on
-   the silk, but it has been marked over.
-
-   See :ref:`this erratum <maple-barrel-jack>` for more information.
+   supplied by up to 18V. (Rev5s manufactured after Spring 2011 may
+   still have this error on the silk, but it has been marked over.) We
+   recommend a barrel jack input voltage **no greater than 12V**, and
+   potentially even lower depending upon the current draw requirements
+   of the application. The same goes for powering off LiPo batteries.
+
+   Please see :ref:`Power Regulation on the Maple
+   <maple-power-regulation>` for more information.
+
+.. _maple-power-regulation:
+
+Power Regulation on the Maple
+-----------------------------
+
+Power regulation on the Maple is provided by two low dropout linear
+voltage regulators. (The part is the MCP1703 from Microchip, in the
+SOT-23A package. You can download the datasheet `here
+<http://ww1.microchip.com/downloads/en/DeviceDoc/22049a.pdf>`_ ). One
+of the regulators supplies power to the digital voltage plane; the
+other supplies power to the analog voltage plane.
+
+These voltage regulators nominally take an input of up to 16V. In
+addition, while the maximum continuous output current for the board is
+250mA, if you are powering the board off higher voltages the amount
+off current it can supply goes down, due to the regulators needing to
+dissipate the extra power. So if you are powering the board off 12V,
+the max current is about 40mA at room temperature. In general (again,
+at room temperature) the max power dissipation (PD) for the chip is
+about .37W, and output current = PD/(Vin-Vout). For exact max current
+calculations, please refer to the datasheet linked above.
+
+If you are planning to draw a lot of current from the Maple board, it
+is necessary to provide input power as close to 3.3V as
+possible. Powering the microcontroller circuitry and LEDs on the board
+alone takes approximately 30mA, so if you are powering the board with
+12V that leaves only 10mA (at best) available for powering any user
+circuitry. Attempting to draw more than 10mA runs the risk of shorting
+out the power regulators and bricking your board.
 
 Using the Built-in Battery Charger
 ----------------------------------
@@ -423,15 +458,16 @@ General
 
 * **Barrel jack power supply voltage mistake**: The acceptable voltage
   range given next to the barrel jack on the Maple through Rev 5s
-  manufactured in Spring 2011 is **incorrect**.  The given range is 7
-  V — 18 V.  In fact, **18 V is too high** and should not be supplied
-  to your board.  The recommended maximum voltage you should apply is
-  **12 V**.
-
-  The original voltage regulators used on the Maple were rated up to
-  18 V.  However, the voltage regulators on current Maple Revs are
-  rated up to 16 V.  Our tests indicate that they operate correctly
-  through 12 V.  We do not recommend higher input voltages.
+  manufactured in Spring 2011 is **incorrect**.  The given range is 7V
+  — 18V.  In fact, **18V is too high** and should not be supplied to
+  your board. The original voltage regulators used on the Maple were
+  rated up to 18V.  However, the voltage regulators on current Maple
+  Revs are rated up to only 16V, and due to the current draw
+  requirements of the board, operate properly only up to 12V.  The
+  recommended maximum voltage you should apply is **12V**, and
+  potentially even lower depending upon the current draw requirements
+  of the application. Please see :ref:`Power Regulation on the Maple
+  <maple-power-regulation>` for more information.
 
 .. _maple-nrst-pb4: