QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 761
LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN
LTC3204-5 and LTC3204-3.3
DESCRIPTION
Demonstration circuit 761 is a low noise regulated
charge pump in 2X2 DFN. There are two assembly
versions, DC761A-A and DC761A-B for featuring the
LTC3204-5 and LTC3204-3.3 respectively. The
DC761A-A produces a regulated 5V output from a
2.7V to 5.5V input. The guaranteed output load cur-
rent is
150mA
for V
IN
between 3.1V and 5.5V, and
65mA for V
IN
less than 3.1V. The DC761A-B produces
a regulated 3.3V output from a 1.8V to 4.5V input.
The guaranteed output current is 50mA from V
IN
be-
tween 1.9V and 4.5V, and 40mA for V
IN
less than
1.9V. The circuit requires only three tiny 0603 surface
mount capacitors and consumes minimal board
space. No inductor and diode are needed. The circuit
features automatic Burst Mode
®
operation at light
loads to maintain low supply current. Built-in soft-
start circuitry prevents excessive inrush current dur-
ing start-up. Thermal shutdown and current-limit cir-
cuitry allow the parts to survive a continuous output
short circuit. These circuits are particularly useful in
systems that require extremely low quiescent current,
such as battery-powered systems.
Design files for this circuit board are available. Call
the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
PERFORMANCE SUMMARY
PARAMETER
Input Voltage Range
DC761A-A (for LTC3204-3.3)
DC761A-A (for LTC3204-5)
Output Voltage V
OUT
3.1V< V
IN
<5.5V, I
OUT
<150mA
2.7V< V
IN
<5.5V, I
OUT
<65mA
DC761A-B (for LTC3204-3.3)
1.9V< V
IN
<4.5V, I
OUT
<50mA
1.8V< V
IN
<4.5V, I
OUT
<40mA
Output Ripple V
OUT
V
IN
= 3.6V, I
OUT
= 150mA (DC761A-A)
V
IN
= 2.4V, I
OUT
= 50mA (DC761A-B)
Nominal Switching Frequency
Efficiency
V
IN
= 3.0V, I
OUT
= 150mA (DC761A-A)
V
IN
= 1.8V, I
OUT
= 25mA (DC761A-B)
20mV
P–P
10mV
P–P
1.2MHz
81.3%
88.7%
50mV
P–P
20mV
P–P
3.168V
3.3V
3.432V
4.8V
5V
5.2V
1.8V
4.5V
CONDITION
DC761A-A (for LTC3204-5)
MIN
2.7V
TYP
MAX
5.5V
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 761
LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN
4.
Turn on the power at the input.
QUICK START PROCEDURE
Demonstration circuit 761 is easy to set up to evalu-
ate the performance of the LTC3204-5 and LTC3204-
3.3. Refer to Figure 1 for proper measurement
equipment setup and follow the procedure below:
measuring the input or output voltage
ripple, care must be taken to avoid a long ground lead
on the oscilloscope probe. Measure the input or out-
put voltage ripple by touching the probe tip directly
across the V
IN
or V
OUT
and GND terminals. See
Figure 2 for proper scope probe technique
.
1.
NOTE:
When
sure that the input voltage does not ex-
ceed 5.5V for DC761A-A or 4.5V for DC761A-B. To
prevent input voltage overshoot when the circuit is
connected to a live supply, an aluminum electro-
lytic capacitor can be added to bypass the V
IN
at
the input terminals. See Linear Technology Applica-
tion Note 88 for a complete discussion.
5.
NOTE:
Make
Check for the proper output voltages. V
OUT
= 4.8V
to 5.2V for DC761A-A, V
OUT
= 3.168V to 3.432V for
DC761A-B
Place jumpers in the following positions:
JP1
ON
6.
there is no output, temporarily disconnect
the load to make sure that the load is not set too
high.
Once the proper output voltages are established,
adjust the loads within the operating range and ob-
serve the output voltage regulation, ripple voltage,
efficiency and other parameters.
NOTE:
If
2.
3.
With power off, connect the input power supply to
V
IN
and GND terminals.
Connect the load between V
OUT
and GND terminals.
Figure 1. Proper Measurement Equipment Setup
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 761
LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN
Figure 2. Measuring Input or Output Ripple
VIN
GND
OPERATING PRINCIPLES
The LTC3204-5/LTC3204-3.3 use a switched capaci-
tor charge pump to boost V
IN
to a regulated voltage.
Regulation is achieved by sensing the output voltage
through an internal resistor divider and modulating
the charge pump output current based on the error
signal. A 2-phase non-overlapping clock activates the
charge pump switches. The flying capacitor is
charged from V
IN
on the first phase of the clock. On
the second phase of the clock, it is stacked in series
with V
IN
and connected to V
OUT
. This sequence of
charging and discharging the flying capacitor contin-
ues at a free running frequency of 1.2MHz.
Other operation principles, such as Burst Mode
®
and
Soft-Start, can be found on the LTC3204-5/LTC3204-
3.3 datasheet at
www.linear.com.
3
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 761
LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN
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