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authorjess b <jessb@leaflabs.com>2011-10-03 09:11:36 -0700
committerMarti Bolivar <mbolivar@leaflabs.com>2011-10-05 12:38:06 -0400
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tree7ee0dca266aba77694967d560a14d48cf12a4f4e /source/hardware/maple-mini.rst
parent5bd0865c807b5270fdb8af77c3c4104dee96d1e2 (diff)
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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>
Diffstat (limited to 'source/hardware/maple-mini.rst')
-rw-r--r--source/hardware/maple-mini.rst51
1 files changed, 40 insertions, 11 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
-------------------