Siemens PL2303 USB-TTL Converter

- Prolific PL2303 USB-serial-bridge
- LT3467A Step-Up DC/DC Converter @ Vout 8,8V
- Unknown circuit powered with 8,8V, perhaps Siemens mobile phone boot ignition impulse

Without any changes, the converter drives 3,3 Volt TTL. Simply remove the Siemens cable and use the pads to connect
PIN 1 as TX (data out from the converter)
PIN 2 as RX (data in to the converter)
PIN 7 as GND

The converter can by modified to drive TTL 5 Volt.
1. Remove diode located next to the PL2303
2. Connect to VDD 5 Volt as shown

The Step-Up converter is set up for 8,8 Volt output and can be reconfigured by changing resistors R1, R2.
1. Disconnect the unknown circuit from the Step-Up converter by cutting conduction path between the two circuits as marked
2. Replace R1, R2 as Vout = 1,255V * (1+ R1 / R2). Default values are R1 = 91k, R2 = 15K
Check out Linear datasheet for details. Download