Functional Description - Silicon Laboratories TS3300 User Manual

1. Functional Description

Boost Regulator Output Voltage Setting
The TS3300 boost regulator is set to an output voltage of 3 V via a resistor divider circuit, as shown in the figure below.
The output feedback (BO FB) pin is 505 mV. It is recommended to use large resistor values to minimize additional current draw at the
output. Resistors values less than 8 MΩ are recommended. Boost output voltage can be set by solving for R3 for a given R6 value in
the following equation:
To set a 3 V output voltage with R6 = 1.37 MΩ, R3 is calculated to be 6.77 MΩ. A 1% standard resistor value of 6.81 MΩ is selected.
This results in an output voltage of 3.02 V.
™
Anti-Crush Voltage Setting
To set the anti-crush voltage, a feedback pin (BI FB) in conjunction with a voltage divider circuit can be implemented, as shown in the
figure below. The feedback pin voltage is 392 mV. It is recommended to use large resistor values to minimize additional current draw at
the input.
Using the following equation to solve for R1 for a given R2 value, the output voltage can be set:
To set a 0.8V output voltage with R2 = 1.37 MΩ, R1 is calculated to be 1.42 MΩ. A 1% standard resistor value of 1.37 MΩ is selected.
This results in an anti-crush voltage of 784 mV. The anti-crush voltage is to be set above the minimum input voltage specification of the
TS3300. Refer to the TS3300 Data Sheet "Applications Information" section for more details.
TS3300 Configurations
The TS3300 can be operated in either a Boost Only Configuration or in a Boost + Output Load Switch Configuration. The TS3300
Demo Board is designed so that both circuit configurations can be evaluated. Two sets of Quick-Start Procedures are provided, detail-
ing how to evaluate each circuit configuration. If the Output Load Switch is not needed, it is recommended to use the Boost Only Con-
figuration, since the lowest quiescent current is achievable this way.
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Figure 1.1. Setting the Boost Output Voltage with a Voltage Divider
R3 =
Figure 1.2. Setting the Anti-Crush Voltage with a Voltage Divider
( V
ANTI −CRUSH
R1 =
( )
V − 0.505 R6
BO
0.505
− 0.392 ) R2
0.392
UG188: TS3300 EVB User's Guide
Functional Description
Rev. 1.1 | 1