QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 862
MICROPWER REGULATED CHARGE PUMP DC/DC CONVERTER
LTC3221-3.3, LTC3221-5 and LTC3221
DESCRIPTION
Demonstration circuit 862 is a micropower regulated
charge pump DC/DC converter with the LTC3221 in a
2mmx2mm DFN package. It comes in three assembly
versions, DC862A-A, DC862A-B and DC862A-C, featur-
ing LTC3221EDC-3.3, LTC3221EDC-5, and LTC3221EDC,
respectively. The DC862A-A generates a fixed 3.3V out-
put. The DC862A-B generates a fixed 5V output. The
DC862A-C generates a programmable regulated 3V out-
put. The maximum output current is
60mA.
The LTC3221 draws ultra low quiescent current at no
load to extend battery life. The quiescent current is even
lower than the self-discharging current of many batter-
ies. By adopting a constant current to charge the output,
the output ripple is low even at high input and light load
Table 1. Performance Summary (T
A
= 25°C)
PARAMETER
Input Voltage Range
CONDITION
DC862A-A
DC862A-B
DC862A-C
Maximum Output Current
DC862A-A: V
IN
> 2V; DC862A-B: V
IN
> 3V;
DC862A-C: V
IN
> 1.8V
DC862A-A
Output Voltage V
OUT
V
IN
> 2V, I
OUT
< 60mA
1.8V < V
IN
< 2V, I
OUT
< 25mA
V
IN
> 3V, I
OUT
< 60mA
2.7V < V
IN
< 3V, I
OUT
< 25mA
V
IN
> 1.8V, I
OUT
< 60mA
DC862A-A
DC862A-B
DC862A-C
V
IN
= 4.4V
V
IN
= 5.5V
V
IN
= 3.8V
600kHz
DC862A-A
Efficiency
DC862A-B
DC862A-C
V
IN
= 2V, I
OUT
= 60mA
V
IN
= 2.7V, I
OUT
= 60mA
V
IN
= 1.8V, I
OUT
= 60mA
82%
86%
82.8%
3.168
MINIMUM
1.8V
2.7V
1.8V
60mA
TYPICAL
MAXIMUM
4.4V
5.5V
3.8V
and is rather constant over the full input voltage range.
This minimizes output capacitor size and reduces solu-
tion cost and space. Built-in soft-start prevents exces-
sive inrush current at turn-on and short-circuit current
limit/thermal protection helps the part survive continu-
ous short-circuit. All these features make the circuit ideal
for the low power and space-constrained applications in
battery powered portable systems.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a trademark of Linear Technology Corporation
3.3
3.432
DC862A-B
DC862A-C
I
OUT
= 0mA
4.8
2.88
5
3
5.2
3.12
40mV
P–P
90mV
P–P
57mV
P–P
Output Ripple V
OUT
(20MHz BW)
I
OUT
= 60mA
Nominal Switching Frequency
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 862
MICROPWER REGULATED CHARGE PUMP DC/DC CONVERTER
QUICK START PROCEDURE
Demonstration circuit 862 is easy to set up to evaluate
the performance of the LTC3221EDC-3.3, LTC3221EDC-
5, and LTC3221EDC. Refer to Figure 1 for proper meas-
urement equipment setup and follow the procedure be-
low:
4.
Turn on the power at the input.
NOTE:
Make sure that the input voltage does not ex-
ceed the corresponding maximum voltage (e.g. 4.4V
for DC862A-A, 5.5V for DC862A-B, 3.8V for DC862A-
C).
5.
measuring the input or output voltage rip-
ple, 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.
2.
NOTE:
When
Check for the proper output voltages. For DC863A-A,
Vout should be within 3.168V to 3.432V. For DC862A-
B, Vout should be within 4.8V to 5.2V. For DC862A-C,
Vout is should be within 2.88V to 3.12V.
Place jumper JP1 to the ON position.
With power off, connect a 1.8V-5.5V power supply to
Vin and GND. The supply should be capable of provid-
ing 200mA current.
Connect a load to Vout and GND.
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, ad-
just the loads within the operating range and observe
the output voltage regulation, ripple voltage, efficiency
and other parameters.
NOTE:
If
3.
Figure 1. Proper Measurement Equipment Setup
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 862
MICROPWER REGULATED CHARGE PUMP DC/DC CONVERTER
Figure 2. Measuring Input or Output Ripple
VIN
GND
OPERATION PRINCIPLES
The LTC3221 family regulator uses a switched capaci-
tor charge pump to boost Vin to a regulated output
voltage. Regulation is achieved by monitoring the out-
put voltage, Vout, using a comparator and keeping it
within a hysteresis window. If Vout drops below the
lower trip point, Vout is charged by the controlled cur-
rent in series with the flying capacitor. Once Vout goes
above the upper trip point, the flying capacitor is dis-
connected from Vout. Vout is discharged and the
flying capacitor is then replenished by the controlled
current for a certain time. Once the lower threshold is
reached, Vout is charged by the controlled current
again.
Burst Mode operation, soft-start and short-circuit
/thermal protection can be found on the LTC3221 data-
sheet at www.linear.com.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 862
MICROPWER REGULATED CHARGE PUMP DC/DC CONVERTER
4
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