Charge Pumps:
Type
Suffix
Connect Pads?
Max Input Voltage Max Current Zener Diode (D2)
LT1054
-
NO
16v
100mA
15v
ICL7660 SCPA
YES
12v
45mA
12v
MAX1044 CPA
YES
10v
20mA
9.1v
TC1044 SCPA
YES
12v
20mA
12v
Type: These are the four most common charge pumps used in guitar effects. However, you should be
able to use any pin compatible charge pump so long as it will accept a 9v input.
Suffix: When ordering parts, make sure you get the ones with these exact suffix. The ICL and TC
brands have both “CPA” and “SCPA” types. You need the “SCPA” type. The MAX one only has the
CPA, but that is the correct one to use for the Road Rage. The LT1054 does not have the CPA or
SCPA category.
The two pads under IC1 must be connected according to the list above. Failure to connect the pads
correctly will result in an audible whine in your audio path. The LT1054 is the only one that does NOT
need the pads connected.
Max Voltage: This is the maximum input voltage the charge pump can accept. Note that when you
use higher input voltages, your outputs will scale accordingly; a 12v in means 24v out instead of 18v.
The 15v output on the RR PCB will still be 15v since that is determined by the regulator.
Max Current: This is very important. This is the maximum amount of current the charge pump can
supply. So, why not use the LT1054 for everything since it has the most current output? Because it is
more expensive. If you are using the Road Rage to run a dirt pedal at 18v, one of the other charge
pumps will suffice 99% of the time since dirt pedals tend to draw low current. However, some effects
(like an analog delay or Univibe) will have higher current consumption. In those cases, the LT1054 is
necessary.
Zener Diode: This diode will protect your IC from an over-voltage supply. This is optional (the 3PRR
work without it) but if you need to protect the circuit from using a wrong power supply, then use this
list to determine what value Zener to use.
Regulators:
The Road Rage is laid out for a TO-92 style regulator. This should suffice in most cases since most
charge pumps tap out at a maximum of 100mA. A TO-220 style regulator will not fit standing up due
to the extra height of the tab on top. You may be able to mount a TO-220 on the bottom of the board
by bending the mounting pins at right angles, but I have not tried this. Keep in mind that the 220
pinout is also the opposite of what’s on the 3PRR PCB.
