QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 863
500MA LOW NOISE, HIGH EFFICIENCY CHARGE PUMP
LTC3203B, LTC3203-1, and LTC3203B-1
DESCRIPTION
Demonstration circuit 863 is a 500mA low noise, high
efficiency charge pump converter with LTC3203 in
3mmx3mm DFN package. It comes with three as-
sembly versions, DC863A-A, DC863A-B and DC863A-
C, featuring the LTC3203B, LTC3203-1, and
LTC3203B-1 respectively. The DC863A-A is pro-
grammed to generate a regulated 3.3V output, and
DC863A-B/DC863A-C generate a user selectable fixed
output voltage of 4.5V or 5V, all from a 2.7V to 5.5V
input. The output current can reach up to
500mA
with
an input voltage above 2.9V (for 4.5V output), 3.1V
(for 5V output) or full input range (for 3.3V output).
By choosing the proper operation modes, the
DC863A circuit optimizes conversion efficiencies and
maintains the maximum output current at each output
voltage. Additionally, DC863A-B features Automatic
Table 1. Performance Summary (T
A
= 25°C)
PARAMETER
Input Voltage Range
Maximum Output Current
DC863A-A: V
IN
> 2.9V; DC863A-B: V
IN
> 3.1V;
DC863A-C: V
IN
> 2.7V
V
IN
> 2.9V, I
OUT
< 500mA
DC863A-B
Output Voltage V
OUT
DC863A-C
2.7V < V
IN
< 2.9V, I
OUT
< 250mA
V
IN
> 3.1V, I
OUT
< 500mA
2.7V < V
IN
< 3.1V, I
OUT
< 150mA
DC863A-A
I
OUT
= 500mA
(20MHz BW)
V
IN
> 2.7V, I
OUT
< 500mA
DC863A-B/-C,
DC863A-A,
V
OUT
= 5V
V
OUT
= 4.5V
V
OUT
= 3.3V
0.9M or 1MHz
DC863A-B
DC863A-C
DC863A-A
V
OUT
= 5V, V
IN
= 2.7V, I
OUT
= 150mA
V
OUT
= 4.5V, V
IN
= 3.8V, I
OUT
= 500mA
V
OUT
= 3.3V, V
IN
= 3.0V, I
OUT
= 500mA
89.5%
77.4%
71.4%
4.32
CONDITION
MINIMUM
2.7V
500mA
TYPICAL
MAXIMUM
5.5V
Burst Mode operation at light load to achieve low
supply current whereas DC863A-A and DC863A-C
operate in constant frequency to achieve low noise at
the input. Also, the built-in soft-start prevents exces-
sive inrush current at turn-on, and short-circuit cur-
rent limit/thermal protection help the part survive a
continuous short-circuit. All these features make the
circuit a powerful solution to the applications that
demand high current with a constrained space in a
battery powered portable system.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a trademark of Linear Technology Corporation
4.5
4.68
4.8
3.168
5
3.3
5.2
3.432
50mV
P–P
50mV
P–P
53mV
P–P
Output Ripple V
OUT
Nominal Switching Frequency
Efficiency
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 863
500MA LOW NOISE, HIGH EFFICIENCY CHARGE PUMP
QUICK START PROCEDURE
Demonstration circuit 863 is easy to set up to evalu-
ate the performance of the LTC3203BEDD,
LTC3203EDD-1 and LTC3203BEDD-1. Refer to
Figure 1 for proper measurement equipment setup
and follow the procedure below:
NOTE:
Make sure that the input voltage does not ex-
ceed 5.5V.
5.
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 Vin or Vout and GND terminals. See
Figure 2 for proper scope probe technique.
1.
NOTE:
When
Check for the proper output voltages. For DC863A-
B and DC863A-C, Vout should measure either a 5V
(could vary from 4.8V to 5.2V) or 4.5V (could vary
from 4.32V to 4.68V) depending on the position of
JP2. For DC863A-A, Vout is typically 3.3V, varying
from 3.168V to 3.432V.
there is no output, temporarily disconnect
the load to make sure that the load is not set too
high.
6.
NOTE:
If
Place jumpers in the following positions:
JP1
JP2
On
5V (or 4.5V)
Connect the JP1 jumper to the “off” position to
turn off the LTC3203. Returning the jumper to the
“on” position will turn on the LTC3203.
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.
2.
3.
4.
With power off, connect a 2.7V-5.5V, 1A power
supply to Vin and GND.
Connect a load to Vout and GND.
Turn on the power at the input.
7.
Figure 1. Proper Measurement Equipment Setup
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 863
500MA LOW NOISE, HIGH EFFICIENCY CHARGE PUMP
Figure 2. Measuring Input or Output Ripple
VIN
GND
OPERATION PRINCIPLES
The LTC3203-1/LTC3203B/LTC3203B-1 use a
switched capacitor charge pump to step up V
IN
to a
regulated output voltage. Regulation is achieved by
sensing the output voltage through a resistor di-
vider and modulating the charge pump output cur-
rent based on the error signal. A two-phase non-
overlapping clock activates the charge pump
switches. The typical frequency of charging and
discharging the flying capacitors is 1MHz (2x
mode) or 0.9MHz (1.5x mode). A unique architec-
ture maintains relatively constant input current for
the lowest possible input noise.
The LTC3203-1/LTC3203B/LTC3203B-1 charge
pump can operate in two modes of voltage conver-
sion: 1.5x or 2x.
In the 1.5x mode the flying capacitors are charged
in series during the first clock phase, and stacked in
parallel on top of V
IN
on the second clock phase.
Alternatively, in the 2x mode the flying capacitors
are charged on alternate clock phases from V
IN
.
While one capacitor is being charged from V
IN
, the
other is stacked on top of V
IN
and connected to the
output. The two flying capacitors operate out of
phase to minimize both input and output ripple.
When the input voltage is higher than the threshold,
the charge pump operates in 1.5x mode and when
the input voltage is lower than the threshold, the
charge pump operates in 2x mode to enhance out-
put current. By properly combining the two modes,
the efficiency, V
OUT
ripple can be optimized for the
required output current.
Burst Mode operation, soft-start and short-circuit
/thermal protection can be found on the LTC3203
datasheet at www.linear.com.
3
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 863
500MA LOW NOISE, HIGH EFFICIENCY CHARGE PUMP
4
京公网安备 11010802033920号
EEWORLD
