MCP16251 and MCP1640B Synchronous Boost Converters Evaluation Board User’s Guide
DS50002110B-page 16 2013 Microchip Technology Inc.
2.3.1.3 EN AND V
OUT
SEL SWITCHES FUNCTION
Table 2-1 shows how the switches affect the functionality of the evaluation board.
Note that SW2 (V
OUT
SEL) and SW4 (EN) are used for the SOT-23-6 circuit. Switches
SW1 (V
OUT
SEL) and SW3 (EN) are used for the 2x3 mm DFN-8 circuit.
2.3.1.4 ADJUSTABLE V
OUT
SETTING
The resistor divider RT and RB are used to set the converter output voltage. By setting
the V
OUT
SEL switch in ON or OFF position, the output voltage can be calculated using
the following equation:
EQUATION 2-1:
TABLE 2-1: FUNCTION OF BOARD SWITCHES
State of Switches V
OUT
[V] for
SW3 or SW4
EN Switch
SW1 or SW2
V
OUT
SEL Switch
MCP16251T-E/CH
SOT-23-6
Converter
MCP1640BT-I/MC
2x3 mm DFN
Converter
ON ON 2 3.3
ON OFF 3.3 5
OFF ON 0 0
OFF OFF 0 0
RT
1
RB
1
V
OUT
V
FB
-------------
1–
=
or
RT
4
RB
2
V
OUT
V
FB
-------------
1–
=
Where: V
FB
= 1.21V for MCP1640B
V
FB
= 1.23V for MCP16251
Note: If the feedback loop is recalculated, the V
OUT
SEL switch will not be used,
as it will add a resistor in parallel with the calculated component.
