IRDC3870

2

A well regulated +12V input supply should be connected to VIN and PGND. A maximum 10A load should

be connected to VOUT and PGND. The connection diagram is shown in Fig. 1 and inputs and outputs of

the board are listed in Table I.

IRDC3870 has three input connectors, one for biasing (PVcc),one for biasing Vcc and the third one as input

voltage (Vin). Separate supplies should be applied to these inputs. PVcc input should be a well regulated

4.5V-5.5V supply and it would be connected to PVcc and PGND and Vcc input should be a well regulated

3.0V-3.6V supply and it would be connected to Vcc and PGND. An external signal can be provided as

Enable signal to turn on or turn off the converter. The absolute maximum voltage of Enable signal is +3.9V.

A well regulated 0-2V signal source is used in this user guide.

The evaluation board is configured for use with 2x10uF (ceramic 0805) + 1x150uF (SP) capacitors.

However, the design can be modified for an all ceramic output cap configuration by adding the inductor

DCR sensing circuit as show in the schematic on page 8.

CONNECTIONS and OPERATING INSTRUCTIONS

LAYOUT

The PCB is a 4-layer board. All layers are 2 Oz. copper. The IR3870 and other components are

mounted on the top and bottom side of the board.

Power supply decoupling capacitors, the Bootstrap capacitor and feedback components are located

close to IR3870. The feedback resistors are connected to the output voltage at the point of regulation

and are located close to IR3870. To improve efficiency, the circuit board is designed to minimize the

length of the on-board power ground current path.

Table I. Connections

Connection

Signal Name

VIN (TP53)

VIN (+12V)

PGND (TP55)

Ground of VIN

PVcc+ (TP61)

PVcc input (+5.0V)

Vcc+ (TP59)

PVcc input (+3.3V)

PGND (TP62)

Ground for PVcc input

PGND (TP60)

Ground for Vcc input

PGND (TB6)

Ground of V

out

VOUT (TB5)

V

Enable (TP52)

Enable input