Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - power management - special purpose 530 µA DFN 12 (4x3)

LTC3625/LTC3625-1

3625f

Typical applicaTion

FeaTures DescripTion

1A High Efﬁciency 2-Cell

Supercapacitor Charger

with Automatic Cell

Balancing

The LTC

3625/LTC3625-1 are programmable supercapaci-

tor chargers designed to charge two supercapacitors in

series to a ﬁxed output voltage (4.8V/5.3V or 4V/4.5V

selectable) from a 2.7V to 5.5V input supply. Automatic

cell balancing prevents overvoltage damage to either

supercapacitor while maximizing charge rate. No balancing

resistors are required.

High efﬁciency, high charging current, low quiescent cur-

rent and low minimum external parts count (one inductor,

one bypass capacitor at V

and one programming resistor)

make the LTC3625/LTC3625-1 ideally suited for small form

factor backup or high peak power systems.

Charging current/maximum input current level is pro-

grammed with an external resistor. When the input supply is

removed and/or the EN pin is low, the LTC3625/LTC3625-1

automatically enter a low current state, drawing less than

1µA from the supercapacitors.

The LTC3625/LTC3625-1 are available in a compact

12-lead 3mm × 4mm × 0.75mm DFN package.

1A SCAP Charger

applicaTions

High Efﬁciency Step-Up/Step-Down Charging of Two

Series Supercapacitors

Automatic Cell Balancing Prevents Capacitor

Overvoltage During Charging

Programmable Charging Current Up to 500mA

(Single Inductor), 1A (Dual Inductor)

= 2.7V to 5.5V

Selectable 2.4V/2.65V Regulation per Cell (LTC3625)

Selectable 2V/2.25V Regulation per Cell (LTC3625-1)

Low No-Load Quiescent Current: 23µA

VOUT

, I

VIN

< 1µA in Shutdown

Low Proﬁle 12-lead 3mm × 4mm DFN Package

Servers, RAID Systems, Mass Storage, High Current

Backup Supplies

Solid State Hard Drives

Wireless Power Meters

High Peak Power Boosted Supplies

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and

ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property

of their respective owners.

Charging Two 2:1 Mismatched Supercapacitors

TIME (SECONDS)

VOLTAGE (V)

40 80 120 160

3625 TA01b

200200 60 100 140 180

OUT

MID

TOP

= 50F

BOT

= 100F

PROG

= 61.9k

CTL = 0

SEL

= 0

OUT

SW1

SW2

MID

PGOOD

PFO

LTC3625

3.3µH

TOP

≥ 0.1F

BOT

≥ 0.1F

OUT

4.8V

3625 TA01a

10µF

2.7V TO 5.5V

PROG

61.9k

PFI

CTL

SEL

3.3µH

Summary of content (16 pages)

PAGE 1
LTC3625/LTC3625-1 1A High Efficiency 2-Cell Supercapacitor Charger with Automatic Cell Balancing Features n n n n n n n n n Description High Efficiency Step-Up/Step-Down Charging of Two Series Supercapacitors Automatic Cell Balancing Prevents Capacitor Overvoltage During Charging Programmable Charging Current Up to 500mA (Single Inductor), 1A (Dual Inductor) VIN = 2.7V to 5.5V Selectable 2.4V/2.65V Regulation per Cell (LTC3625) Selectable 2V/2.
PAGE 2
LTC3625/LTC3625-1 Absolute Maximum Ratings (Note 1) Pin Configuration VIN, VOUT (Transient) t < 1ms, Duty Cycle < 1%........................................... –0.3V to 7V VIN, VOUT, VMID, PGOOD, CTL, PROG, PFI, PFO.................................... –0.3V to 6V EN, VSEL. .......................................... –0.3V to VIN + 0.3V VOUT Short-Circuit Duration.............................. Indefinite IPGOOD, IPFO............................................................50mA IPROG. ....................
PAGE 3
LTC3625/LTC3625-1 Electrical Characteristics The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, RPROG = 143k, unless otherwise specified. SYMBOL PARAMETER CONDITIONS TYP MAX UNITS IVIN Input Operating Current, ISW1 = ISW2 = 0µA, No Switching CTL = VIN, VMID = 1.5V, VOUT = 2.5V (Boost Only) CTL = VIN, VMID = 1.5V, VOUT = 3.5V (Buck Only) CTL = 0, VMID = 1.5V, VOUT = 2.
PAGE 4
LTC3625/LTC3625-1 Electrical Characteristics Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LTC3625/LTC3625-1 internal switches are guaranteed to survive up to 3A of peak current. Internal current limits will restrict peak current to lower levels.
PAGE 5
LTC3625/LTC3625-1 Typical Performance Characteristics TA = 25°C, L1 = 3.3µH, L2 = 3.3µH, CIN = 10µF, CTOP = CBOT , LTC3625 unless otherwise specified. Buck Input Power vs RPROG VIN = 5.5V VMID = 2.65V CTL = 0V VSEL = VIN 5 4 3 85 80 75 70 65 60 1 0 55 VIN = 3.6V VMID = 2V CTL = 0V 50 200 50 100 150 200 250 300 350 400 450 500 RPROG (kΩ) 0 700 Buck Efficiency vs VMID 1700 1200 IBUCK (mA) RPROG = 143k 2 RPROG = 286k 0.2 0.6 1.0 1.4 1.8 VMID (V) 2.2 VIN = 5.5V VSEL = VIN CTL = 0 2.
PAGE 6
LTC3625/LTC3625-1 Typical Performance Characteristics TA = 25°C, L1 = 3.3µH, L2 = 3.3µH, CIN = 10µF, CTOP = CBOT , LTC3625 unless otherwise specified. VMID SINGLE INDUCTOR APPLICATION 0 6 VOUT 4 VMID 2 0 DUAL INDUCTOR APPLICATION 0 20 40 60 80 100 120 TIME (SECONDS) 140 Charge Profile with CTOP > CBOT VOUT VIN = 3.6V, VSEL = 3.
PAGE 7
LTC3625/LTC3625-1 Pin Functions VMID (Pin 10): Midpoint of Two Series Supercapacitors. The pin voltage is monitored and used, along with VOUT , to enable or shut down the buck and boost converters during charging to achieve voltage balancing of the top and bottom supercapacitors. SW2 (Pin 12): Switch Pin for the Boost Regulator. External inductor connects between the SW2 pin and VMID. If CTL is logic high, then SW2 must be connected to SW1. GND (Exposed Pad Pin 13): Ground.
PAGE 8
LTC3625/LTC3625-1 Operation The LTC3625/LTC3625-1 are dual cell supercapacitor chargers. Their unique topology charges two series connected capacitors to a fixed output voltage with programmable charging current without overvoltaging either of the cells — even if they are severely mismatched. No balancing resistors are required.
PAGE 9
LTC3625/LTC3625-1 Operation Single Inductor Operation With the CTL pin tied to VIN the LTC3625/LTC3625-1 will operate in single inductor mode. In this mode the same inductor serves in the power path for both the buck and the boost converters. Thus, the buck converter and boost converter will never run simultaneously. Under certain conditions with a single inductor, a small amount of current can flow from the supercapacitors to VIN when the boost charger is active.
PAGE 10
LTC3625/LTC3625-1 Operation converter will turn off. Once VMID has again risen above the VMID(GOOD) threshold, the boost converter will be re-enabled. In the case where VOUT < VMID, the boost converter will operate in trickle charge mode until VOUT exceeds VMID (see Boost Converter). 3. During phase 2, if CBOT exceeds its individual maximum threshold voltage (2.45V/2.05V typical if VSEL is low or 2.7V/2.
PAGE 11
LTC3625/LTC3625-1 Applications Information Programming Charge Current/Maximum Input Current VIN Capacitor Selection The CBOT charge current is programmed with a single resistor connecting the PROG pin to ground. The program resistor and buck output current are calculated using the following equation: The style and value of capacitors used with the LTC3625/ LTC3625-1 determine input voltage ripple.
PAGE 12
LTC3625/LTC3625-1 Applications Information The buck and boost converters are designed to work with inductors over a wide range of inductances. Choosing a higher valued inductor will decrease operating frequencies, while a lower valued inductor will increase frequency but also increase peak current overshoot/undershoot. For most applications a 3.3µH inductor is recommended. To maximize efficiency, choose an inductor with a low DC resistance.
PAGE 13
LTC3625/LTC3625-1 Applications Information board ground. Failure to make thermal contact between the exposed pad on the backside of the package and the copper board will result in higher thermal resistances. resistance can be kelvined out by a dedicated voltage sense trace from the VMID pin to a point halfway between the bottom plate of CTOP and the top plate of CBOT . In the case of CTOP , however, it is even more critical to keep any resistance in the connection to a minimum.
PAGE 14
LTC3625/LTC3625-1 Typical Applications Solar Powered SCAP Charger with MPPT D1 CMSH3-40 R4 10k R1 26.7k + C4 390µF 16V VOUT SW1 EN C1 10µF LTC3625 PFI GND C5 10nF C3 1F GND R3 143k 4 – 5 V+ LT1784CS5 – 3 + V 2 D2 1.2V C2 1F L2 3.3µH SW2 PROG R5 174k R2 10.0k L1 3.3µH VMID VSEL C6 100pF D3 SOLAR PANEL 6.0V OPEN CIRCUIT 4.
PAGE 15
LTC3625/LTC3625-1 Typical Applications 12V Power Ride-Through IDEAL DIODE LTC4355 FDS3672 12V LT1737 FLYBACK 4 • 10 • 2 • GND DC-A CTL EN 7 11 • LT1737 VIN VOUT LTC3625 SW1 L2 3.3µH VMID VSEL C2 100F PROG R1 143k DC-C GND GND GND UV DETECTOR *EXPOSED PAD TO BE CONNECTED TO A THERMAL PAD ISOLATED FROM THE SYSTEM GROUND 8 12 FDS3672 C1 100F SW2 GND DC-B L1 3.3µH 1.8V VOUT LTM4601A M1 IRF7424 * 6 DC/DC VIN * VIN CTL EN VOUT LTC3625 L3 3.3µH C3 100F SW1 L4 3.
PAGE 16
LTC3625/LTC3625-1 Typical Application Minimum External Component Application (500mA Charge Current) VIN* 2.7V TO 5.5V C1 10µF NC NC VIN VOUT SW1 LTC3625 L1 3.3µH VOUT 4.8V/5.3V C2 ≥ 0.1F SW2 PFI CTL EN VSEL PGOOD PFO PROG GND VMID C3 ≥ 0.1F 3625 TA02 *25mA MINIMUM LOAD REQUIRED ON VIN Related Parts PART NUMBER DESCRIPTION COMMENTS LTC3203/LTC3203B/ LTC3203B-1/LTC3203-1 500mA Low Noise High Efficiency Dual Mode Step-Up Charge Pumps VIN: 2.7V to 5.