LP3905SD-30EV National Semiconductor, LP3905SD-30EV Datasheet - Page 2

• Manufacturer Part Number: LP3905SD-30EV
• Description: BOARD EVALUATION LP3905SD-30
• Manufacturer: National Semiconductor

Specifications of LP3905SD-30EV

• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 4, Non-Isolated
• Voltage - Output: 1.2V, 1.875, 2.8V, 2.8V
• Current - Output: 600mA, 600mA, 100mA, 100mA
• Voltage - Input: 3 ~ 5.5V
• Regulator Topology: Buck
• Frequency - Switching: 2MHz
• Board Type: Fully Populated
• Utilized Ic / Part: LP3905
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

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Connection Information
Connect a supply voltage (3.0V to 5.5V) to either of the VIN
pins on the evaluation board. LK4 hardwired on the board
connects both the BUCK supply side to the LDO supply side.
These supplies are both required to correctly power the de-
vice.
Supply ground may be connected at either GND or BKGND.
LK3 which is hardwired on the eval board connects the BUCK
gnd to the LDO gnd.
For best results in current measurements on the Buck out-
puts, use 4 wire measurement techniques to eliminate any
voltage drop on the PCB traces or connecting wires to the
loads. For this the instrument sense connection should be
connected to the corresponding buck ‘S’ (sense) connection
on the evaluation board.
Input leads should be kept reasonably short to minimize in-
ductance.
ON/OFF control is provided by logic signals on EN1 and EN2.
A minimum of 1.2V is required on these pins to enable the
corresponding outputs. The outputs will be shutdown with the
enable pins set to 0.4V or less. If ON/OFF control is not re-
quired, then either or both enable pins may be connected to
V
trix.
A number of control options are provided on board by either
hardwiring or using reconfigurable links on the 4-way matrix.
Link Matrix Details
Link Link Connection Description
1 - 2
3 - 4
1 - 2
1 - 3
IN
-
either externally or by using the on-board connection ma-
3 - 4 EN1 and EN2 connect to VIN supply. All
-
-
-
-
outputs power on with the supply voltage.
EN1 connects to EN2 and may be driven
externally from one source to control all
outputs.
EN1 conencts to VIN. Buck1, LDO1, and
LDO2 outputs are enabled at device power up.
Buck 2 should be enabled separately using an
external source connected to EN2.
EN2 conencts to VIN. Buck 2 is enabled at
device power up. Buck1, LDO1, and LDO2
outputs should be enabled using an external
source connected to EN1.
Both EN1 and EN2 can be driven separately
from external sources connected at the board
inputs EN1 and EN2.
2
PCB Layout
PCB Component and Pin Layout
Board SIze 1.5" x 1.3"
Link Matrix Diagram
20198102
20198105