Power supply

How RockBLOCK manages power

The internal Iridium module requires a very stable voltage source during short bursts of high current while transmitting. All versions of RockBLOCK contain a voltage regulation circuit which includes a super-capacitor that meets the demands of the Iridium module and simplifies the power requirements from your host system.

When power is first applied to RockBLOCK, the super capacitor is charged. The Iridium module will only be switched on once sufficient charge has been accumulated. This is typically a delay of about 10 seconds.

It is possible to switch off the RockBLOCK, but maintain the charge in the super capacitor to ensure an immediate startup. Please refer to the On/Off control section below.

DC supply

The host system must provide DC power to RockBLOCK. Nominally this is 5V for RockBLOCK 9602/9603 and 12-24V (e.g. vehicle power supply) for the RockBLOCK Plus.


Power Supply Limit:

You do not need to limit the current from your power supply - RockBLOCK has its own current limiter.

You can supply a limited current, but this will affect the charging time of the supercapacitor, which means slower startup from cold, and may mean you have to pause for a few seconds between successive transmissions to avoid brownout.

Minimum (V)Maximum (V)Maximum (mA)
RockBLOCK 9603 (5V)3.05.4470
RockBLOCK 9603 (3.7V)3.55.4470
RockBLOCK 9602 (5V)4.55.4470
RockBLOCK Plus9.030.0225


RockBLOCK 9603 - Primary Power Pin

There is a Schottky diode (D1) between the Li-Ion (Pin 9) and the common 5V rail (Pin 8). This is designed to protect a 3.7V battery from a higher voltage supplied to the 5V input.

If you are only planning to provide low voltage and do not require the battery protection provided by the D1 diode then you should connect your power source directly to the 5V pin (Pin 8).


Can I add/remove/modify?

We get quite a few questions about the power supply of RockBLOCK 9603. If you want to know about modifying RockBLOCK, check out the FAQs.


RockBLOCK Plus (FAQ)

  • Circuit Protection: When installing RockBLOCK Plus in a vehicle, it is recommended that a 2A inline fuse be used.
  • Polarity Protection: The RockBLOCK Plus is equipped with reverse polarity protection.
  • Load Protection: RockBLOCK Plus is designed to operate through voltage transients and survive large temporary voltages observed in vehicle starting.

Alternate Power Supply

If you have an alternative power supply that can meet the peak requirements (1.5A @ 5V for ~10ms) it is possible to provide power using the β€˜Li-Ion’ pin. This can be used with input voltages from 2.8V to 5.4V (it is dangerous to exceed 5.4V as it will result in over-charging the supercapacitor). It works well with Lithium-Ion cells.

This feature is available on both 9602 and 9603 versions, but the implementation has been greatly improved with the RockBLOCK 9603. Specifically, the old implementation didn't limit the in-rush current, there is now a specific pin for this purpose, which offers some protection to the battery.


If powering using the β€˜Li-Ion’ pin, there is no need to provide 5V to any other pin.
We would recommend cutting the USB power supply (red) in the FTDI cable.

Current consumption

Idle average* (mA)Maximum (mA)Off (ΞΌA)
RockBLOCK 9603 (5V)4047045
RockBLOCK 9602 (5V)5047020
RockBLOCK Plus (12V)1622520

*The Idle measurements are taken over a 3 minute period of inactivity (no radio transmission), with the Iridium module powered on. In this mode, you will observe regular bursts of approx 100mA every 20 seconds. The module will receive ring alerts in this mode.

On/Off control

The On/Off control enables the host controller to put RockBLOCK into a minimal-power 'off' mode. The internal supercapacitor charge is maintained so that RockBLOCK can be used immediately when switching back on.

If you do not need this functionality, it is recommended that you do not connect the On/Off control. It can be left floating, and RockBLOCK will remain on when powered.

Off (V)On (V)Absolute Max (V)Absolute Min (V)
RockBLOCK 9602/9603 (pre-v3.F)< 2.0>
RockBLOCK 9603 (v3.F)GroundFloating5.00.0
RockBLOCK Plus< -1.5> 1.530.0-30.0


RockBLOCK 9603 v3.F

Due to supply-chain shortage, some components in RockBLOCK 9603 3.F have been replaced with alternatives. This does not adversely affect the normal operation of the device.

Because of these component changes, 3.F now includes a transistor circuit on the On/Off control pin to ensure correct power up at all supply voltages. The On/Off control pin should not be clamped below the RockBLOCK supply voltage and should be disconnected/left floating to turn on.


RockBLOCK 9603 v3.F

The above change has introduced a potential issue when interfacing directly to a 3V3 microcontroller pin while supplying the RB with 5V.
The new On/Off circuitry now provides a high impedance (1Meg resistor) to the super cap voltage, equal to the supplied voltage. This may exceed the maximum IO voltage of the micro.
If the RB was supplied by 5V, the connecting device should also be 5V tolerant. If not, it is recommended to use an interfacing circuit, eg MOSFET, transistor, relay, etc. to connect to a microcontroller.


RockBLOCK 9603 PRE-v3.F

For pre-3.F boards, the On/Off control pin should not be clamped below the RockBLOCK supply voltage as excessive leakage current out of the On/Off pin can cause the device to turn off. To turn on, the pin should be disconnected/left floating.

Load dump protection

RockBLOCK Plus is designed to operate through voltage transients and survive large temporary voltages observed in vehicle starting.

LED indications

The RockBLOCK 9603 (only) has two LEDs to indicate power status. The Red LED indicates the presence of a DC power supply. The Green LED indicates that the super capacitor has sufficient charge to switch on the Iridium module, and successfully transmit.

If the Green LED is flashing, this can indicate the modem is drawing too much current from the supply. Try connecting the unit to another supply ie a USB power supply instead of a computer. If it is still flashing, this can indicate a faulty modem or cable.