Question: Can the S6BP203A output 3.8 V for powering a 4G module?
Answer: 4G remote wireless communication module is included in the Telematics Box (T-Box) application. Many 4G modules require 3.8 V power supply (for example, http://www.telit.com/cellular/). Cypress automotive PMIC S6BP203A can be configured as follows for powering a 4G module.
Add two resistors to the FB pin as shown in Figure.1 instead of connecting the FB pin directly to the VOUT rail.
The tuned output voltage is calculated as follows:
To minimize the influence of the FB pin input resistance RFB, R1 and R2 should be lesser than RFB, which is 2.53 MΩ (minimum) as shown in the datasheet. For 3.8 V output, the recommended value for R1 and R2 is: R1=36 kΩ, R2=270 kΩ.
As the side effect, R1 and R2 cause an little additional load current, ⁄( 1 + 2). With the recommended resistor value, additional input current at no load condition will be lower than 10 µA.
Some 4G modules need 3A pulse current. Figure 2 shows the transient waveform of S6BP203A with 3A pulse load current
(0.05Aßà 3.1A). The output voltage can keep over 3.3 V.
The instantaneous load current time (t) is limited by S6BP203A temperature rise (ΔT) as shown in Figure 3. For example, under Ta=105°C condition, the temperature rise must be less than Tjmax – Ta = 45°C. Therefore, the duty of 3A instantaneous load current should be less than 47%.
Figure 2. Transient Waveform with 3A Pulse Load Current
Figure 3. Temperature Rise versus 3A Instantaneous Load Current Duty