Fiche technique pour DC1220B Quick Start Guide de Analog Devices Inc.

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DC1220B QUICK START GUIDE
1
DESCRIPTION
Demonstration circuit DC1220B is a Low Profile Regu-
lated Dual Cell SuperCAP Charger featuring the LTC3225.
The LTC3225 is a constant-current SuperCAP charger
designed to charge two SuperCAPs in series to a fixed
output voltage of 4.8V/5.3V from a 2.9V to 5.5V input
supply. Automatic cell balancing is achieved during the
charging phase.
Low input noise, low quiescent current and low external
parts count make the LTC3225 ideally suited for small,
battery-powered applications. Charging current level is
programmed through an external resistor. Internal cur-
rent limit and thermal shutdown circuitry allows the part
to survive a continuous short-circuit from PROG to GND.
When the input supply is removed, the LTC3225 auto-
matically enters a low current state, drawing less than
1μA from the SuperCAPs.
The LTC3225 is offered in a 10-lead (3mm
×
2mm) DFN
package.
Design files for this circuit board are available. Call
the LTC factory.
L, LTC, LTM, LT, Burst Mode, are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TABLE 1. TYPICAL SPECIFICATIONS (25
°
C)
Input Voltage Range: V
CC
2.9V to 5.5V
Charge Current 30mA or 150mA dependant on JP3 setting
VOUT 4.8V or 5.3V dependant on JP2 setting
OPERATING PRINCIPLES
The LTC3225 is a dual cell SuperCAP charger using
a constant-current/constant-voltage algorithm. Its
ability to control input charge currents up to 300mA
and achieve automatic cell balancing during charg-
ing makes it well suited for charging two series
connected SuperCAPs. The LTC3225 includes an
internal switched capacitor charge pump to boost
Vin to a regulated output voltage. A unique architec-
ture maintains relatively constant input current for
the lowest possible input noise. The basic charger
circuit requires only three external components.
DC1220B
QUICK START GUIDE
LTC3225EDDB
Low Profile Regulated Dual Cell SuperCAP Charger
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DC1220B QUICK START GUIDE
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QUICK START PROCEDURE
Using short twisted pair leads for any power connec-
tions and with all loads and power supplies off, refer
to Figure 1 for the proper measurement and equip-
ment setup.
1. Jumper and Load Settings to start:
JP1 (RUN) = SHDN
JP2 (VOUT SELECT) = 5.3V
JP3 (Iin LIMIT) = 30mA
LOAD1 = off
2. Set VIN to 3.0V and verify that the input current
is less than 10mA. Verify that VOUT is less than
3.8V indicating that the SuperCAP is in a low
charge state.
3. Set JP1 to the RUN position. Verify that the input
current is ~60mA. Verify that VOUT is less than
4.0V and that PGOOD is low.
4. Monitor PGOOD and VOUT. When PGOOD goes
high, verify that VOUT is ~5.0V.
5. Verify that VOUT is ~5.3V when the input current
drops to less than 10mA indicating a fully charged
capacitor.
6. Turn on Load1 and set to 50mA. Monitor PGOOD
and VOUT. When PGOOD goes low, verify that
VOUT is ~4.9V.
7. Set JP1 to SHDN and allow the SuperCAP to dis-
charge to 1.5V at which point Load1 will be set to
0mA and turned off.
8. Set JP3 to 150mA
9. Set JP1 to the RUN position. Verify that the input
current is ~300mA. Verify that PGOOD is low.
10. Monitor PGOOD and VOUT. When PGOOD goes
high, verify that VOUT is ~5.0V.
11. Verify that VOUT is ~5.3V when the input current
drops to less than 10mA indicating a fully charged
capacitor.
12. Turn on Load1 and set to 200mA. Monitor PGOOD
and VOUT. When PGOOD goes low, verify that
VOUT is ~4.9V.
13. Set JP1 to SHDN, increase Load1 to 500mA and
allow the SuperCAP to discharge to 1.5V at which
point Load1 will be set to 0mA and turned off.
14. Set JP2 to 4.8V
15. Set JP1 to the RUN position. Verify that the input
current is ~300mA. Verify that PGOOD is low.
16. Monitor PGOOD and VOUT. When PGOOD goes
high, verify that VOUT is ~4.55V.
17. Verify that VOUT is ~4.8V when the input current
drops to less than 10mA indicating a fully charged
capacitor.
18. Turn on Load1 and set to 200mA. Monitor PGOOD
and VOUT. When PGOOD goes low, verify that
VOUT is ~4.45V.
19. Set JP1 to SHDN, increase Load1 to 500mA and
allow the SuperCAP to discharge to 1.0V at which
point Load1 will be set to 0mA and turned off.
APPLICATION INFORMATION
This demo circuit is designed to demonstrate the full
capability of the LTC3225 Low Profile Regulated Dual
Cell SuperCAP Charger. Not all components are re-
quired in all applications. The critical circuit compo-
nents are on the top of the board near the IC and
listed in the Required Circuit Components section of
the Bill of Materials, see Figure 4.
The style and value of the input capacitors C2 and C6
controls the amount of ripple present at the input pin
(Vin). To reduce noise and ripple, it is recommended
that a low equivalent series resistance (ESR) multi-
layer ceramic chip capacitor (MLCCs) be used. A
10nH inductor between C6 and C2 will reject fast cur-
DC1220B QUICK START GUIDE
3
rent notches thereby presenting a nearly constant load
to the input power supply. For economy, the 10nH
inductor can be fabricated on the PC board with a
PC board trace of 1 cm in length.
The amount of current drawn from VIN to charge the
SuperCAP is programmed using a single resistor from
the PROG pin to ground. The charge current (referred
to VIN) is approximately 1600 times the current out of
the PROG pin.
The power efficiency of the LTC3225 is similar to that
of a linear regulator with an effective input voltage of
twice the actual input voltage. In an ideal voltage
doubler the power efficiency would be 50%. At mod-
erate to high output power the switching losses and
quiescent current of the LTC3225 are negligible thus
this estimate of efficiency is valid.
The flying capacitor controls the strength of the
charge pump. In order to achieve the rated output cur-
rent, it is necessary to have 0.6μF of capacitance for
the flying capacitor. Ceramic capacitors of different
materials lose their capacitance with higher tempera-
ture and voltage at different rates. When comparing
different capacitors, it is often more appropriate to
compare the amount of achievable capacitance for a
given case size rather than comparing the specific ca-
pacitance value. For example, a 4.7μF 10V Y5V ce-
ramic capacitor in a 0805 case may not provide any
more capacitance than a 1μF 10V X5R or X7R ceramic
capacitor in the same 0805 case. In fact the 1μF 10V
X5R or X7R ceramic capacitor will provide more ca-
pacitance than the 4.7μF 10V Y5V ceramic capacitor.
The manufacture’s data sheet should be consulted to
determine what value of capacitor is needed to ensure
that the minimum capacitance values are met over the
operating temperature and bias voltage.
Output voltage programming is accomplished by set-
ting the VSEL pin either high or low. A high (VSEL>
1.3V) will set the output threshold voltage to 5.3V
while a low (VSEL < 0.4V) will set the output thresh-
old voltage to 4.8V.
For higher input voltages and maximum output cur-
rent, there can be substantial power dissipation in the
LTC3225. To reduce the maximum junction tempera-
ture, a good thermal connection to the PC board is
recommended. Connecting the GND pin (pin 8) and
the exposed pad (Pin 11) of the DFN package to a
ground plane under the device on two layers of the PC
board can reduce the thermal resistance of the pack-
age and the PC board considerably.
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DC1220B QUICK START GUIDE
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Figure 1.
Proper Measurement Equipment Setup
VIN
GND
Figure 2.
Measuring Input or Output Ripple
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DC1220B QUICK START GUIDE
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Figure 3.
Circuit Schematic
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DC1220B QUICK START GUIDE
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Item Qty Reference - Des Part Description Manufacturer, Part #
REQUIRED CIRCUIT COMPONENTS:
1 1 C1 CAP, CHIP, X7R, 1uF, 10% 10V, 0603
Murata,
GRM188R71A105KA61D
2 1 C2 CAP, CHIP, X7R, 2.2uF, 10% 10V, 0603
Murata,
GRM188R71A225KE15D
3 2 C5, C6 CAP, CHIP, X7R, 0.22uF, 10% 6.3V, 0603
Murata,
GRM188R70J224KA88D
4 1 COUT SUPERCAP, 0.20F, 5.5V CAP-XX, HS203F
5 1 R1 RES, 60.4K OHM, 1%, 1/16W, 0402
VISHAY,
CRCW040260K4FKED
6 1 R2 RES, 15K OHM, 1%, 1/16W, 0402
VISHAY,
CRCW040215K0FKED
7 1 U1 Low Profile Regulated Dual Cell Super-
CAP Charger LTC3225EDDB
ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS:
1 0 OPT-C3, OPT-C4 SUPERCAP 2.5V OR 2.7V
2 3 R3,R4,R5 RES, 100K OHM, 5%, 1/16W, 0402 VISHAY, CRCW0402100KJNED
HARDWARE FOR DEMO BOARD ONLY:
1 7
E1,E2,E3,E4,E5,
E6, E7 TURRET, 0.09 DIA MILL-MAX, 2501-2
2 3 JP1,JP2,JP3 HEADER, 3 PINS, 2mm SAMTEC, TMM-103-02-L-S
3 3 JP1,JP2,JP3 SHUNT 2MM SAMTEC, 2SN-BK-G
4 4
STAND-OFF, NYLON 0.375" tall (SNAP
ON) KEYSTONE,8832 (SNAP ON)
Figure 4.
Bill of Materials