LP3905SD-A3EV National Semiconductor, LP3905SD-A3EV Datasheet - Page 7

• Manufacturer Part Number: LP3905SD-A3EV
• Description: BOARD EVALUATION LP3905SD-A3
• Manufacturer: National Semiconductor

Specifications of LP3905SD-A3EV

• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 4, Non-Isolated
• Voltage - Output: 1.5V, 1.85V, 2.8V, 3V
• 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: -

Typical Application Circuit
Functional Description
POWER UP/DOWN PROCEDURE
The LP3905 Bucks and LDOs are powered UP/DOWN with
2 control pins, EN1 and EN2. In order for the enable pins to
operate, V
than V
EN1 and EN2 can be controlled fully independently.
LDOs will be turned on only after Buck1 is powered up. LDOs are powered on simultaneously.
In case EN1 and EN2 are enabled at the same time, power up of Buck2 is delayed by 50µs in order to minimize the inrush current
from the battery.
When EN1 and EN2 are disabled, the relevant output voltages are turned off.
UVLO_R
IN1
and V
(specified in electrical characteristic). Once
IN2
should be set to a voltage level higher
FIGURE 5. Typical Application Circuit For Adjustable Device
FIGURE 6. LP3905 Power UP/DOWN Timing Sequence
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enabled, EN1 will turn on Buck1, LDO1 and LDO2. EN2 can
independently be used to enable Buck2. Figure 6 illustrates
the power UP/DOWN timing sequence of the LP3905 blocks
for V
Both linear regulators have active pulldowns when the out-
puts are disabled.
EN
≥ V
IH (min)
(enable) and V
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EN
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≤V
IL (max)
(disable).
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