2.1 Typical usage
2.2 Block diagram
2.3 Voltage supervisor
2.4 Voltage regulator
2.5 Automatic power switch
3.2 Minimal size
The Mini-Battery-Supervisor is a tiny circuit (30x18mm)
which enables you to use a battery pack as power supply for
low-power USB electronic appliances.
More precisely, the Mini-Battery-Supervisor has four purposes:
- It reduces the voltage provided by the battery to 5V, which is the maximal
voltage expected by USB powered appliances;
- It monitors the battery voltage to cleanly cut the appliance power supply
when the battery is fully unloaded, in order to protect the appliance and
- It makes it possible to connect simultaneously the battery and an external
USB host to the appliance, for configuration and diagnosis purposes;
- It features a rugged panel-mount USB Micro-B connector, which can be
integrated in the front panel of an enclosure for instance.
Yoctopuce thanks you for buying this Mini-Battery-Supervisor and sincerely hopes that
you will be fully satisfied with it. The Yoctopuce engineers have put a large amount of effort
to ensure your Mini-Battery-Supervisor is easy to install anywhere. If you are nevertheless
disappointed with this product, do not hesitate to contact Yoctopuce support.
|1:||USB Micro-B 2.0 connector (host port)||4:||Battery pads|
|2:||Battery pads ||5:||Battery type selection|
|3:||Socket to appliance ||DIP switches|
2.1. Typical usage
The Mini-Battery-Supervisor is intended to be mounted on the front panel of an enclosure,
containing the appliance and its battery. This provides an easy access to
the USB connector for diagnosis whenever needed. The battery is in a holder
box and is connected to the Mini-Battery-Supervisor using a pair of wires. The appliance
is connected to the Mini-Battery-Supervisor through the white 1.27mm (1.25mm) pitch connector,
using a USB-MicroB-1.27-25 or 1.27-1.27-11 cable.
Typical usage of the Mini-Battery-Supervisor
2.2. Block diagram
The functions implemented by the Mini-Battery-Supervisor are described below:
Mini-Battery-Supervisor block diagram
2.3. Voltage supervisor
The Mini-Battery-Supervisor measures the voltage provided by the batteries in order
to power off the appliance when the battery is empty, and to turn it
on again when the battery has been replaced. In order to avoid for the
appliance to turn on again by itself when the empty battery voltage rises
as the load is removed, the turn-on voltage level is much higher than
the turn-off limit. Two DIP switches make it possible to choose among
four voltage limits, which have been carefully selected to match the
most useful battery types:
|Battery type||Turn-off level||Turn-on level|
The voltage levels above are measured at the circuit input, and are defined
with a tolerance of ±0.05V. Depending on the current consumption, on
the length and on the section of the cable between the battery and the Mini-Battery-Supervisor,
switching levels at the battery may be slightly higher. Similarly, the resulting
voltage levels at the appliance will be lower, in particular due to the voltage
dropout in the linear regulator (see below).
Caution: Due to the voltage dropout on the regulator, the first two power
sources in the table above are the only ones that guarantee that at any time the
power supply conforms to USB 2.0 specifications. When using 4C NiMH or 1S LiPo,
the appliance receives a voltage lower than 4.5V, which may work with some
appliances but not with all of them. Many Yoctopuce devices can work properly
with 4C NiMH.
2.4. Voltage regulator
The Mini-Battery-Supervisor includes a regulator intended to bring down
the battery voltage level to a value that is acceptable for USB appliances,
i.e. no more than 5V. Given the tiny size of the Mini-Battery-Supervisor, we use a simple
low-dropout (LDO) regulator, which lowers the voltage by dissipating
the extra energy as heat. It is a valid solution for low-power appliances
that stay in deep sleep during extended periods of time, but some limitations
must be taken into account:
- When the battery voltage goes down to the 5V target voltage and below, the
output voltage goes down as well and is always under the battery voltage,
with a step down of approximately 1mV per mA. The Mini-Battery-Supervisor does not include
any extra component to bring the voltage up to 5V.
- The energy dissipated by the regulator is limited to 1W. Therefore, the maximum
continuous tolerated current is 500mA for batteries up to 6.5V and
250mA up to 8.5V (2 LiPo cells). Peeks up to 1.5A are however acceptable.
The regulator is driven by the voltage supervisor and entirely disconnected
when the power-down level is reached, in order to reduce the current consumption
to the very minimum in order to protect the battery. The values below have been
measured at the time when the power-down level is reached:
|Battery type||Quiescent current|
Moreover, in order to ensure that the appliance is powered off properly,
and to reduce the risk of flash memory corruption that a progressive
power brown-out would cause, the output voltage is actively pulled to
0V as soon as the voltage regulator is shut down.
2.5. Automatic power switch
When a USB host is connected to the panel-mount USB Micro-B connector,
the power source is automatically switched to this source. In this way,
regardless of the battery state, it is possible to communicate with the
appliance over the USB cable. The switch from one power source to the
other does not cause any power cut on the appliance.
The ground wire (GND) of the USB host and of the battery are connected
together. The supply lines however are switched and protected to prevent
current from flowing back from one source to the other.
Note that this USB power switching feature is in itself a good reason for
using the Mini-Battery-Supervisor even without any battery, for instance when a USB appliance
needs to be powered from a fixed power supply but that an USB connection is
In order to make it possible to use the Mini-Battery-Supervisor in small enclosures,
the connection to the appliance is made using a small 1.27mm (1.25mm)
pitch connector. If the appliance also has pads for a 1.27mm connector,
as all Yoctopuce devices do, then you can use a 1.27-1.27-11 cable,
available on the Yoctopuce web shop .
Using a 1.27-1.27-11 cable to connect the appliance.
If the appliance is powered by a USB A or USB Micro-B 2.0 cable and if your enclosure
is large enough, you can simply use a USB-A-1.27-25 cable or a USB-MicroB-1.27-25 cable. This saves you the work of soldering
a 1.27mm connector.
Using a USB-MicroB-2.17-25 cable to connect the appliance.
If you want to integrate the Mini-Battery-Supervisor to an enclosure, the typical solution
is to cut in the enclosure front panel an opening corresponding to the USB
Micro-B connector according to the template provided at the end of this manual,
and to affixate the Mini-Battery-Supervisor with screw directly on the panel.
Be aware that the panel mount screw of this USB Micro-B connector are not
metric screw but imperial #2-56 screw. They are provided together with the
The exact reference of the USB Micro-B connector is article MUSB-K552-30,
manufactured by Amphenol ICC. In order to protect it from dust, you can
add the MUSB2K15015BP dust cover, available from major electronic component
In case you do not want to make the USB connector visible, you can also fix
the Mini-Battery-Supervisor within your enclosure or on another circuit, using the four
fixing points on the corners of the PCB. They are designed for M2.5 screw,
with a head no larger then 4.5mm. In order to avoid damaging the components under
the PCB, use M2.5 threaded spacers between the Mini-Battery-Supervisor and the fixing plane.
You can find a set of M2.5 screw and spacers on Yoctopuce web shop under the
3.2. Minimal size
If you opt for the panel-mount solution to fix the Mini-Battery-Supervisor and if you
need to reduce its size to the very minimum, you can split the two side bands
of the circuit using a simple plier: the PCB had a V-break cut to make this
simple and risk-free. This removes the extra fixing holes and the DIP switch
legend, but the circuit length is shortened to 21mm instead of 30mm.
How to make the Mini-Battery-Supervisor as small as possible.
You can find below a summary of the main technical characteristics
of your Mini-Battery-Supervisor module.
|USB connector||micro-B |
|Max Current (continuous)||500 mA|
|Max Current (peak)||1.5 A|
|Threshold voltage||3.5 / 4.5 / 5 / 6.4 V|
|IEC protection class||class III |
|Normal operating temperature||5...40 ░C|
|Extended operating temperature||-40...85 ░C|