LTC3204BEDC-3.3#TRMPBF Linear Technology, LTC3204BEDC-3.3#TRMPBF Datasheet - Page 8

• Manufacturer Part Number: LTC3204BEDC-3.3#TRMPBF
• Description: IC SW CAP/DBLR 3.3V 50MA 6DFN
• Manufacturer: Linear Technology
• Type: Switched Capacitor (Charge Pump), Doublerr

Specifications of LTC3204BEDC-3.3#TRMPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 3.3V
• Current - Output: 50mA
• Frequency - Switching: 1.2MHz
• Voltage - Input: 1.8 ~ 4.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 6-DFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: LTC3204BEDC-3.3#TRMPBFTR

APPLICATIO S I FOR ATIO
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
Power Efficiency
The power efficiency (η) of the LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5 is similar to that of a linear
regulator with an effective input voltage of twice the actual
input voltage. This occurs because the input current for a
voltage doubling charge pump is approximately twice the
output current. In an ideal regulating voltage doubler the
power efficiency would be given by:
At moderate to high output power, the switching losses
and the quiescent current of the LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5 are negligible and the expres-
sion above is valid. For example, with V
100mA and V
is 81.8% which is in close agreement with the theoretical
83.3% calculation.
Maximum Available Output Current
For the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/
LTC3204B-5,the maximum available output current and
voltage can be calculated from the effective open-loop
output resistance, R
2V
From Fig. 1, the available current is given by:
Effective Open Loop Output Resistance (R
The effective open loop output resistance (R
pump is a very important parameter which determines the
strength of the charge pump. The value of this parameter
depends on many factors such as the oscillator frequency
8
IN(MIN)
I
η =
OUT
P
=
OUT
P
.
IN
2
Figure 1. Equivalent Open-Loop Circuit
V
IN
OUT
=
R
–
V
OL
V
regulating to 5V, the measured efficiency
OUT
V
IN
+
–
OUT
U
• 2
2V
OL
R
•
OL
I
IN
I
OUT
, and the effective input voltage,
OUT
U
=
V
2
OUT
V
I
OUT
IN
3204 F01
W
+
–
V
OUT
IN
OL
OL
= 3V, I
) of a charge
)
U
OUT
=
(f
time, the internal switch resistances (R
the external capacitors. A first order approximation for
R
Typical R
in Figure 2.
V
ThestyleandvalueofcapacitorsusedwiththeLTC3204-3.3/
LTC3204-5/LTC3204B-3.3/LTC3204B-5 determine several
important parameters such as regulator control loop sta-
bility, output ripple, charge pump strength and minimum
start-up time.
To reduce noise and ripple, it is recommended that low
ESR (<0.1Ω) ceramic capacitors be used for both C
C
and aluminum capacitors are not recommended because
of their high ESR.
The value of C
ripple for a given load current. Increasing the size of C
will reduce the output ripple at the expense of higher
minimum turn-on time. The peak-to-peak output ripple
is approximately given by the expression:
IN
OUT
OSC
OL
R
V
, V
RIPPLE P P
is given below:
OL
. These capacitors should be 1µF or greater. Tantalum
), value of the flying capacitor (C
OUT
≅ ∑
OL
S=1 TO 4
2
Capacitor Selection
(
values as a function of temperature are shown
Figure 2. Typical R
−
R
8
7
6
5
4
–50
OUT
S
)
V
V
≅
+
IN
OUT
directly controls the amount of output
= 2.7V
2
f
= 4.5V
OSC
f
OSC
I
OUT
TEMPERATURE (°C)
•
1
0
•
C
C
FLY
OUT
OL
vs Temperature
50
FLY
S
), the nonoverlap
), and the ESR of
3204 F02
100
IN
3204fa
and
OUT