LM3670MFX-2.5 National Semiconductor, LM3670MFX-2.5 Datasheet - Page 12

• Manufacturer Part Number: LM3670MFX-2.5
• Description: Miniature Step-Down DC-DC Converter for Ultra Low Voltage Circuits
• Manufacturer: National Semiconductor

www.national.com
Operation Description
Soft-Start
The LM3670 will have a soft-start circuit that limits in-rush
current during start-up. Typical currents and times are:
Note 4: The first 32µS are to allow the bias currents to stabilize
LDO - Low Drop Out Operation
The LM3670 can operate at 100% duty cycle (no switching,
PMOS switch completely on) for low drop out support of the
output voltage. In this way the output voltage will be con-
trolled down to the lowest possible input voltage.
Current (mA)
140
280
620
70
0
FIGURE 5. Operation in PFM Mode and Transfer to PWM Mode
until soft start ends
Duration (µSec)
(Continued)
224
256
256
32
12
The minimum input voltage needed to support the output
voltage is
• I
• R
• R
PFET
LOAD
DSON,
INDUCTOR
Load current
Drain to source resistance of PFET switch
in the triode region
Inductor resistance
20075803