QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 916
LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN
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LTC3204B-5 and LTC3204B-3.3
DESCRIPTION
Demonstration circuit 916 is a low noise regulated
charge pump in 2X2 DFN. There are two assembly
versions, DC916A-A and DC916A-B for featuring
LTC3204B-5 and LTC3204B-3.3 respectively. The
DC916A-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 DC916A-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 constant frequency operation at any load.
Built-in soft-start circuitry prevents excessive inrush
current during start-up. Thermal shutdown and cur-
rent-limit circuitry allow the parts to survive a con-
tinuous output short circuit from V
OUT
to GND. These
circuits are particularly useful in applications that re-
quire low V
OUT
ripple and extremely small size.
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 CONDITION MIN TYP MAX
DC916A-A (LTC3204B-5) 2.7V 5.5V
Input Voltage Range
DC916A-B (LTC3204B-3.3) 1.8V 4.5V
DC916A-A (LTC3204B-5)
3.1V< V
IN
<5.5V, I
OUT
<150mA
2.7V< V
IN
<5.5V, I
OUT
<65mA
4.8V 5V 5.2V
Output Voltage V
OUT
DC916A-B (LTC3204B-3.3)
1.9V< V
IN
<4.5V, I
OUT
<50mA
1.8V< V
IN
<4.5V, I
OUT
<40mA
3.168V 3.3V 3.432V
V
IN
= 3.6V, I
OUT
= 150mA (DC916A-A) 20mV
P–P
50mV
P–P
Output Ripple V
OUT
V
IN
= 2.4V, I
OUT
= 50mA (DC916A-B) 10mV
P–P
20mV
P–P
Nominal Switching Frequency 1.2MHz
V
IN
= 3.0V, I
OUT
= 100mA (DC916A-A) 81.2%
Efficiency
V
IN
= 1.8V, I
OUT
= 20mA (DC916A-B) 90.2%
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 916
LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN
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QUICK START PROCEDURE
Demonstration circuit 916 is easy to set up to evalu-
ate the performance of the LTC3204B-5 and
LTC3204B-3.3. Refer to Figure 1 for proper meas-
urement equipment setup and follow the procedure
below:
NOTE:
When 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.
Place jumpers in the following positions:
ON
2.
With power off, connect the input power supply to
V
IN
and GND terminals.
3.
Connect the load between V
OUT
and GND terminals.
4.
Turn on the power at the input.
NOTE:
Make sure that the input voltage does not ex-
ceed 5.5V for DC916A-A or 4.5V for DC916A-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.
Check for the proper output voltages. V
OUT
= 4.8V
to 5.2V for DC916A-A, V
OUT
= 3.168V to 3.432V for
DC916A-B
NOTE:
If there is no output, temporarily disconnect
the load to make sure that the load is not set too
high.
6.
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.
Figure 1.
Proper Measurement Equipment Setup
VIN
GND
Figure 2.
Measuring Input or Output Ripple
JP1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 916
LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN
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OPERATING PRINCIPLES
The LTC3204B-5/LTC3204B-3.3 use 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 by 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.
The LTC3204B datasheet gives complete description
of the part, operation and application information. The
datasheet must be read in conjunction with this quick
start guide for demo circuit 916.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 916
LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN
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