LM3350 National Semiconductor, LM3350 Datasheet - Page 4

• Manufacturer Part Number: LM3350
• Description: Switched Capacitor Voltage Converter
• Manufacturer: National Semiconductor

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Typical Performance Characteristics
V
Switching Frequency vs
Temperature
Pin Description
Pin
out
1
2
3
4
5
6
7
8
vs I
Enable
Cap1+
Cap1−
Cap2+
Cap2−
load
Name
V
V
Gnd
high
low
(Step-Down)
Positive terminal for the first charge
pump capacitor.
Negative terminal for the first charge
pump capacitor.
Positive terminal for the second charge
pump capacitor.
Negative terminal for the second charge
pump capacitor.
In Step-Up mode, this will be the input
terminal. In Step-Down mode, this will
be the output terminal.
Ground
In Step-Down mode, this will be the
input terminal. In Step-Up mode, this
will be the output terminal.
Active high CMOS logic level Enable
Input. Connect to Voltage Input terminal
to enable the IC. Connect to Ground
(Pin 6) to disable.
DS100002-10
DS100002-5
Function
P vs I
load
(Step-Down)
(Continued)
4
Detailed Operation
OPERATING PRINCIPLE
The LM3350 is a charge-pump voltage converter that pro-
vides a voltage conversion ratio of 3/2 in step-up mode and
a conversion ratio of 2/3 in the step-down mode. Thus it can
be used in the step-down mode to provide a 3.3V output
from a regulated 5V input or in the step-up mode to provide
a 5V output from a regulated 3.3V input. Other values of in-
put voltages can be used as long as they are within the lim-
its.
The LM3350 contains an array of CMOS switches which are
operated in a certain sequence to provide the step-up or
step-down of the input supply. An internal RC oscillator pro-
vides the timing signals.
Energy transfer and storage are provided by four inexpen-
sive ceramic capacitors. The selection of these capacitors is
explained in the Capacitor Selection section under Applica-
tion Information.
DS100002-7
Output Source Impedance vs
Temperature (Step-Down)
DS100002-8