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LTC3225/LTC3225-1

3225fb

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

150mA Supercapacitor

Charger

The LTC

3225/LTC3225-1 are programmable supercapaci-

tor chargers designed to charge two supercapacitors in

series to a selectable ﬁ xed output voltage (4.8V/5.3V for

the LTC3225 and 4V/4.5V for the LTC3225-1) from input

supplies as low as 2.8V to 5.5V. Automatic cell balancing

prevents overvoltage damage to either supercapacitor. No

balancing resistors are required.

Low input noise, low quiescent current and low external

parts count (one ﬂ ying capacitor, one bypass capacitor at

and one programming resistor) make the LTC3225/

LTC3225-1 ideally suited for small battery-powered

applications.

Charge current level is programmed with an external

resistor. When the input supply is removed, the LTC3225/

LTC3225-1 automatically enter a low current state, drawing

less than 1A from the supercapacitors.

The LTC3225/LTC3225-1 are available in a 10-lead 2mm

× 3mm DFN package.

Low Noise Constant Frequency Charging of Two

Series Supercapacitors

Automatic Cell Balancing Prevents Capacitor

Overvoltage During Charging

Programmable Charge Current (Up to 150mA)

Selectable 2.4V or 2.65V Regulation per Cell

(LTC3225)

Selectable 2V or 2.25V Regulation per Cell

(LTC3225-1)

Automatic Recharge

VIN

= 20µA in Standby Mode

COUT

< 1µA When Input Supply is Removed

No Inductors

Tiny Application Circuit (2mm × 3mm DFN Package,

All Components <1mm High)

Current Limited Applications with High Peak Power

Loads (LED Flash, PCMCIA Tx Bursts, HDD Bursts,

GPRS/GSM Transmitter)

Backup Supplies

Charging Proﬁ le with 30% Mismatch

in Output Capacitance, C

TOP

< C

BOT

L, LT, LTC and LTM are registered trademarks and ThinSOT is a trademark of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

–

SHDN

SEL

ON/OFF

OUTPUT

PROGRAMMING

OUT

GND

PGOOD

PROG

LTC3225

LTC3225-1

100k

0.6F

12k

3225 TA01a

1µF

2.2µF

OUT

4.8V/5.3V (LTC3225)

4V/4.5V (LTC3225-1)

2.8V/3V TO 5.5V

SHDN

5V/DIV

COUT

2V/DIV

TOP

-V

BOT

200mV/DIV

VIN

300mA/DIV

5 SEC/DIV

3225 TA01b

LTC3225

SEL

= V

PROG

= 12k

TOP

= 1.1F

BOT

= 1.43F

TOP

INITIAL VOLTAGE = 0V

BOT

INITIAL VOLTAGE = 0V

Summary of content (14 pages)

PAGE 1
LTC3225/LTC3225-1 150mA Supercapacitor Charger FEATURES DESCRIPTION n The LTC®3225/LTC3225-1 are programmable supercapacitor chargers designed to charge two supercapacitors in series to a selectable ﬁxed output voltage (4.8V/5.3V for the LTC3225 and 4V/4.5V for the LTC3225-1) from input supplies as low as 2.8V to 5.5V. Automatic cell balancing prevents overvoltage damage to either supercapacitor. No balancing resistors are required.
PAGE 2
LTC3225/LTC3225-1 ABSOLUTE MAXIMUM RATINGS (Note 1) PIN CONFIGURATION VIN, COUT to GND ......................................... –0.3V to 6V SHDN, VSEL ...................................... –0.3V to VIN + 0.3V COUT Short-Circuit Duration ............................. Indeﬁnite IVIN Continuous (Note 2) ......................................350mA IOUT Continuous (Note 2) .....................................175mA Operating Temperature Range (Note 3).... –40°C to 85°C Storage Temperature Range..............
PAGE 3
LTC3225/LTC3225-1 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 3.6V, CIN = 2.2μF, CFLY = 1μF, unless otherwise speciﬁed (Note 3). SYMBOL PARAMETER CONDITIONS MIN VIN Input Voltage Range VSEL = VIN VSEL = 0 l l 2.8 2.8 VCOUT Charge Termination Voltage Sleep Mode Threshold (Rising Edge) VSEL = VIN VSEL = 0 l l 4.4 3.
PAGE 4
LTC3225/LTC3225-1 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C, CFLY = 1μF, CIN = 2.2μF, CTOP = CBOT , unless otherwise speciﬁed) IOUT vs RPROG IOUT vs VOUT (RPROG = 12k) 160 VIN = 3.6V VOUT = 4.5V (LTC3225) 140 100 160 90 80 140 120 70 80 60 EFFICIENCY (%) 120 100 IOUT (mA) IOUT (mA) Efﬁciency vs VIN 180 100 80 60 40 20 20 0 0 20 10 30 50 40 RPROG (kΩ) 60 0.5 1 1.5 2 2.5 3 VOUT (V) 3.5 4 4.5 3225 G01 0 VOUT = 4.5V VOUT = 3.7V 25 TA = 85°C 20 TA = 25°C VOUT = 3.
PAGE 5
LTC3225/LTC3225-1 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C, CFLY = 1μF, CIN = 2.2μF, CTOP = CBOT , unless otherwise speciﬁed) Charging Proﬁle with Unequal Initial Output Capacitor Voltage (Initial VTOP = 1V, VBOT = 1.
PAGE 6
LTC3225/LTC3225-1 SIMPLIFIED BLOCK DIAGRAM CFLY 9 1 2 C+ VIN 4 C– VIN SHDN SOFT-START AND SHUTDOWN CONTROL UVLO THERMAL PROTECTION 3000i POR 1.2V COUT CX CHARGE PUMP RUN CTOP 3 CBOT GND 8 i 7 10 PROG CLK RPROG RUN/STOP R1 OSCILLATOR – C1 R2 + VREF – 2% 1.2V PGOOD VREF + 1.088V (LTC3225) 1.067V (LTC3225-1) 6 POR VREF – 6% VSEL VREF – 7.2% 5 C2 – 3225 F01 Figure 1 OPERATION The LTC3225/LTC3225-1 are dual cell supercapacitor chargers.
PAGE 7
LTC3225/LTC3225-1 OPERATION Once the output voltage is charged to the preset voltage threshold, the part shuts down the internal charge pump and enters into a low current state. In this state, the LTC3225/LTC3225-1 consume only about 20μA from the input supply. The current drawn from COUT is approximately 2μA. Automatic Cell Balancing Due to manufacturing tolerances, capacitance and leakage current can vary from supercapacitor to supercapacitor.
PAGE 8
LTC3225/LTC3225-1 APPLICATIONS INFORMATION Programming Charge Current Charging Time Estimation The charge current is programmed with a single resistor connecting the PROG pin to ground.
PAGE 9
LTC3225/LTC3225-1 APPLICATIONS INFORMATION VIN Capacitor Selection The type and value of CIN controls the amount of ripple present at the input pin (VIN). To reduce noise and ripple, it is recommended that low equivalent series resistance (ESR) multilayer ceramic chip capacitors (MLCCs) be used for CIN. Tantalum and aluminum capacitors are not recommended because of their high ESR.
PAGE 10
LTC3225/LTC3225-1 APPLICATIONS INFORMATION Table 1 contains a list of ceramic capacitor manufacturers and how to contact them. Table 1. Capacitor Manufacturers also be generated if the ﬂying capacitors are far from the part (i.e. the loop area is large). To prevent capacitive energy transfer, a Faraday shield may be used. This is a grounded PC trace between the sensitive node and the LTC3225/LTC3225-1 pins.
PAGE 11
LTC3225/LTC3225-1 TYPICAL APPLICATION 5V Supercapacitor Back-Up Supply Q2 Si4421DY LTM4616 VIN1 VOUT1 VIN 5V VIN2 C6 100μF FB1 R3 4.78k C5 22μF Q1 Si4421DY 1.8V GND ITHM1 1.2V VOUT2 C7 100μF FB2 VIN COUT C+ C1 1μF C4 2.
PAGE 12
LTC3225/LTC3225-1 PACKAGE DESCRIPTION DDB Package 10-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1722 Rev Ø) 0.64 p0.05 (2 SIDES) 3.00 p0.10 (2 SIDES) R = 0.05 TYP 0.70 p0.05 2.55 p0.05 1.15 p0.05 PACKAGE OUTLINE 0.25 p 0.05 0.50 BSC 2.39 p0.05 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.200 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 6 0.40 p 0.10 10 2.00 p0.10 (2 SIDES) 0.75 p0.05 0.64 p 0.05 (2 SIDES) 5 0.25 p 0.05 0 – 0.05 PIN 1 R = 0.20 OR 0.
PAGE 13
LTC3225/LTC3225-1 REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION PAGE NUMBER B 6/10 Updated Note 3 in Electrical Characteristics section. 2, 3 Updates to Pins 8 and 11 in Pin Functions. 5 Update to text in Layout Considerations section. 10 Updated Typical Application and Related Parts. 14 3225fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use.
PAGE 14
LTC3225/LTC3225-1 TYPICAL APPLICATION 12V Supercapacitor Back-Up Supply LT3740 HIGH EFFICIENCY DOWN CONVERTER D1 CSHD6-40C DPAK VIN 12V VIN+ + GND C1 47μF 25V DCAP VOUT LT3740 GND VOUT 1.8V 10A GND GND * CHARGER 3 C2 1μF 10V VIN COUT LTC3225/ LTC3225-1 C+ CX C– GND 10A D2 CMSH3-20 VBIAS 3.3V C5 10μF GND 1 M4 Si4410DY D3 CMSH3-20 CHARGER 2 D4 CMSH3-20 VIN COUT LTC3225/ LTC3225-1 C+ CX C3 1μF 10V 8 VM VCC LTC2915 7 2 SEL1 SEL2 6 3 TOL/MR RT 5 4 GND RST R7 10k R1 2k C6 0.