DC761A - Demo Manual

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 current is 150mA for VIN between 3.1V and 5.5V, and
65mA for VIN 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 VIN between 1.9V and 4.5V, and 40mA for VIN 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 softstart circuitry prevents excessive inrush current during start-up. Thermal shutdown and current-limit circuitry 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
CONDITION
MIN
TYP
MAX
DC761A-A (for LTC3204-5)
2.7V
5.5V
DC761A-A (for LTC3204-3.3)
1.8V
4.5V
Input Voltage Range
DC761A-A (for LTC3204-5)
Output Voltage VOUT
3.1V< VIN <5.5V, IOUT<150mA
4.8V
5V
5.2V
3.168V
3.3V
3.432V
VIN = 3.6V, IOUT = 150mA (DC761A-A)
20mVP–P
50mVP–P
VIN = 2.4V, IOUT = 50mA (DC761A-B)
10mVP–P
20mVP–P
2.7V< VIN <5.5V, IOUT<65mA
DC761A-B (for LTC3204-3.3)
1.9V< VIN <4.5V, IOUT<50mA
1.8V< VIN <4.5V, IOUT<40mA
Output Ripple VOUT
Nominal Switching Frequency
Efficiency
1.2MHz
VIN = 3.0V, IOUT = 150mA (DC761A-A)
81.3%
VIN = 1.8V, IOUT = 25mA (DC761A-B)
88.7%
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 761
LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN
4.
NOTE: Make sure that the input voltage does not exceed 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 electrolytic capacitor can be added to bypass the VIN at
the input terminals. See Linear Technology Application Note 88 for a complete discussion.
QUICK START PROCEDURE
Demonstration circuit 761 is easy to set up to evaluate the performance of the LTC3204-5 and LTC32043.3. Refer to Figure 1 for proper measurement
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 output voltage ripple by touching the probe tip directly
across the VIN or VOUT and GND terminals. See
Figure 2 for proper scope probe technique.
1.
5.
6.
ON
2.
With power off, connect the input power supply to
VIN and GND terminals.
3.
Connect the load between VOUT and GND terminals.
Check for the proper output voltages. VOUT = 4.8V
to 5.2V for DC761A-A, VOUT = 3.168V to 3.432V for
DC761A-B
NOTE: If there is no output, temporarily disconnect
the load to make sure that the load is not set too
high.
Place jumpers in the following positions:
JP1
Turn on the power at the input.
Once the proper output voltages are established,
adjust the loads within the operating range and observe the output voltage regulation, ripple voltage,
efficiency and other parameters.
Figure 1. Proper Measurement Equipment Setup
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 761
LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN
GND
VIN
Figure 2. Measuring Input or Output Ripple
OPERATING PRINCIPLES
The LTC3204-5/LTC3204-3.3 use a switched capacitor charge pump to boost VIN 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 VIN on the first phase of the clock. On
the second phase of the clock, it is stacked in series
with VIN and connected to VOUT. This sequence of
charging and discharging the flying capacitor continues 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/LTC32043.3 datasheet at www.linear.com.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 761
LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN
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