MAX17710_1107_技术文档

19-5872; Rev 1; 7/11

E V A L U A T I O N K I T A V A I L A B L E

MAX17710

Energy-Harvesting Charger and Protector

General Description

Features

The MAX17710 is a complete system for charging and

protecting micropower-storage cells such as Infinite Power

Solution’s THINERGY^®microenergy cells (MECs). The IC

can manage poorly regulated sources such as energy-

harvesting devices with output levels ranging from 1FW to

100mW. The device also includes a boost regulator circuit

for charging the cell from a source as low as 0.75V (typ).

An internal regulator protects the cell from overcharging.

S Integrated Power-Management IC for Energy

Storage and Load Management

S Lithium Charger

1nA Standby I

QBATT

625nA Linear Charging

1µW Boost Charging

S Lithium Cell Undervoltage Protection

S Charger Overvoltage Shunt Protection

Output voltages supplied to the target applications are

regulated using a low-dropout (LDO) linear regulator with

selectable voltages of 3.3V, 2.3V, or 1.8V. The output regu-

lator operates in a selectable low-power or ultra-low-power

mode to minimize drain of the cell. Internal voltage protec-

tion prevents the cell from overdischarging.

S 1.8V, 2.3V, or 3.3V LDO (150nA I

)

QBATT

S Lithium Cell Output Buffering

S Ultra-Thin, 3mm x 3mm x 0.5mm UTDFN Package

The device is available in an ultra-thin, 3mm x 3mm x

0.5mm 12-pin UTDFN package.

Ordering Information appears at end of data sheet.

Applications

Powered/Smart Cards

Medical Devices

For related parts and recommended products to use with this part,

refer to: www.maxim-ic.com/MAX17710.related

Remote Wireless

Sensors

High-Temperature

Applications

Memory and Real-Time

Clock Backup

Military/DoD and

Aerospace

Semiactive RFID Tags

Toys

Simplified Operating Circuit

UNREGULATED

OUTPUT

THINERGY

MEC101

PCKP

BATT

SEL2

CHG

RF OR OTHER

HIGH-VOLTAGE

SOURCE

REGULATED

OUTPUT

REG

MAX17710

TEG, SOLAR,

OR OTHER

LX

LOW-VOLTAGE

SOURCE

LDO

AE

CONTROL

SIGNALS

FB

EP

LCE

GND

PGND SEL1

THINERGY is a registered trademark of Infinite Power Solutions, Inc.

�� Maxim Integrated Products

1

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

MAX17710

Energy-Harvesting Charger and Protector

ABSOLUTE MAXIMUM RATINGS

BATT to GND...........................................................-0.3V to +6V

CHG to GND ...........................................................-0.3V to +6V

LX to PGND.............................................................-0.3V to +6V

GND to PGND ......................................................-0.3V to +0.3V

FB, AE, LCE, SEL1, SEL2, REG,

Continuous Power Dissipation (T = +70NC)

A

12-Pin UTDFN (derate 15mW/NC above +70NC) .......1200mW

Operating Temperature Range.......................... -40NC to +85NC

Junction Temperature .....................................................+150NC

Storage Temperature Range............................ -65NC to +150NC

Lead Temperature (soldering, 10s) ................................+300NC

Lead Temperature (reflow)..............................................+260NC

PCKP to GND.......................................-0.3V to V

CHG Continuous Current

+ 0.3V

BATT

(limited by power dissipation of package) ...................100mA

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-

tion of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute

maximum rating conditions for extended periods may affect device reliability.

ELECTRICAL CHARACTERISTICS

(V

= +4.3V, Figure 1, T = -40NC to +85NC, unless otherwise noted. Typical values are at T = +25NC.) (Note 1)

A A

CHG

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

5.3

MAX

5.7

UNITS

CHG Input Maximum Voltage

CHG Enable Threshold

Limited by shunt regulator (Note 2)

4.875

4.07

V

4.15

4.21

CE

CHG Quiescent Current

CHG Shunt Delay

I

V

= 4.0V rising, V = 4.0V

BATT

625

25

1300

nA

Fs

QCHG

CHG

CHG Input Shunt Limit

(Note 2)

input current limited by Absolute

Maximum Ratings

50

mA

V

CHG

CHG Maximum Input Current

50

100

mA

V

= 4.0V, I

= 1FA

45

55

CHG

BATT

= -6mA

= -20mA

= -40mA

CHG-to-BATT Dropout Voltage

mV

65

100

BATT REG

BATT Regulator Voltage

BATT Regulation Delay

4.065

4.125

30

4.160

V

= 4.2V, starting at 4V

Fs

CHG

Regulator in dropout;

= 4.15V, V

450

1

1030

165

V

= 4.12V

BATT

CHG

Harvest standby (AE pulse low)

= 0V, V = 2.1V to 4.0V

V

CHG

BATT

BATT Quiescent Current

I

QBATT

nA

AE regulator on, boost off;

= 0V, V = 4.0V, AE high

725

150

1650

550

V

CHG

BATT

LCE regulator on, boost off;

= 4.0V, LCE mode (Note 3)

V

BATT

�� Maxim Integrated Products

2

MAX17710

Energy-Harvesting Charger and Protector

ELECTRICAL CHARACTERISTICS (continued)

(V

= +4.3V, Figure 1, T = -40NC to +85NC, unless otherwise noted. Typical values are at T = +25NC.) (Note 1)

A A

CHG

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

LINEAR LDO REGULATOR

V

= 4.0V, I

= 50FA, SEL1 = open

3.22

2.25

1.75

2.9

3.3

2.3

1.8

3.3

2.3

1.8

3.37

2.375

1.9

PCKP

REG

REG Voltage

= 4.0V, I

= 50FA, SEL1 = GND

= 50FA, SEL1 = BATT

= 50FA, SEL1 = open

= 50FA, SEL1 = GND

= 50FA, SEL1 = BATT

V

3.7

REG Voltage, LCE Mode

(Note 3)

2.1

2.5

V

1.6

2.05

= 2.15V, V

= 3.8V, AE high

75

mA

FA

REG

PCKP

REG Current Limit

= 2.15V, V

= 3.8V, LCE mode

REG

PCKP

50

(Note 3)

REG Startup Time

V

= 4.0V, AE rising, C = 1FF

REG

5.3

ms

PCKP

SEL1 = open

SEL1 = GND

SEL1 = BATT

SEL1 = open

SEL1 = GND

SEL1 = BATT

2.175

1.575

1.30

LCE Threshold High (Note 4)

V

IH-LCE

0.9

0.6

0.5

LCE Threshold Low (Note 5)

V

IL-LCE

PCKP REGULATOR

AE Threshold High

AE Threshold Low

V

1.13

-4

V

IH-AE

V

0.15

3.78

IL-AE

V

= 0V, persists < 1Fs

= 0V, persists > 1Fs

= 3.6V

-2

1

FA

nA

V

AE

AE Low Input Current

AE High Input Current

PCKP Enable Threshold

PCKP Charge Current

1

REG enabled

3.62

3.7

100

V

= 0V, V

= 2.2V

mA

PCKP

BATT

V

= 4.0V, resistance between BATT

PCKP Impedance Ramp Rate

5

ms

s

and PCKP from high impedance to 5I

BATT Undervoltage Lockout

(UVLO) Delay

V

= 2.15V, AE high, first ramp of

= 2.15V, AE high, not first PCKP

BATT

t

UVLO1

PCKP

V

ramp

BATT

BATT UVLO Delay

0.5

ms

V

UVLO2

AE regulator active, LCE regulator inactive

LCE regulator active, AE regulator inactive

1.990

2.15

3

2.30

BATT UVLO Threshold

�� Maxim Integrated Products

3

MAX17710

Energy-Harvesting Charger and Protector

ELECTRICAL CHARACTERISTICS (continued)

(V

= +4.3V, Figure 1, T = -40NC to +85NC, unless otherwise noted. Typical values are at T = +25NC.) (Note 1)

A A

CHG

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

BOOST REGULATOR

CHG Regulation Voltage

Frequency

V

= 4.125V

4.3

4.5

1

4.7

V

BATT

= 3.9V, V

= 3.95V

0.73

1.27

MHz

ns

CHG

Boost Turn-On Time

t

Design guidance, typical only

Rising (enable)

850

0.75

0.25

600

0.5

8

BOOST-ON

FB

0.485

0.22

1.0

ON

FB Threshold

V

nA

I

FB

Falling (disable), V

= 3.8V

0.27

OFF

CHG

FB Input Current Low

LX nMOS On-Resistance

V

= GND, momentary

FB

I

= 20mA, V

= 3.8V, SEL2 = GND

= 3.8V, SEL2 = open

0.275

4

0.7

12

LX

BATT

R

DS-ON

= 10mA, V

Note 1: Specifications are 100% production tested at T = +25NC. Limits over the operating temperature range are guaranteed by

A

design and characterization.

Note 2: Since the CHG shunt regulator has a 25Fs delay, the user must limit the voltage to the Absolute Maximum Rating until the

internal CHG shunt provides the voltage limit at the pin in response to 50mA input. Larger currents must be shunted with

an external clamp to protect the CHG pin from damage.

Note 3: LCE mode is entered by pulsing AE high, then pulsing AE low.

Note 4: For logic-high, connect LCE to the REG output. Do not connect to the BATT or PCKP pins.

Note 5: Since LCE is compared to the REG pin voltage for operation, the low-power regulator cannot be switched off under condi-

tions where the REG output is shorted to GND.

�� Maxim Integrated Products

4

MAX17710

Energy-Harvesting Charger and Protector

Table 1. Summary of Typical Quiescent Current vs. Operating Conditions

I

TOTAL QUIESCENT

CURRENT (nA)

QBATT

(nA)

QCHG

(nA)

NAME

MODE

CONDITIONS

Cell Connection:

Regulator outputs off,

no charger present

Cell connected to circuit

during assembly

Standby

1

—

1 (from cell)

UVLO or Shutdown:

Regulator outputs off,

no charger present

V

falls below 2.15V

BATT

Shutdown

1 (from cell)

or AE and LCE pulsed low

Charger Present:

Regulator outputs off,

cell charging

V

= 4V,

626 (from energy-harvesting

cell); can harvest down to

1µW

CHG

Full Charge

> V

625

CHG

BATT,

AE pulsed low

Charger in Dropout:

V

= 4.15V,

= 4.12V,

CHG

Dropout

Charge

Regulator outputs off,

charger present, but

below regulation voltage

450

—

450 (from cell)

BATT

AE pulsed low

AE Regulator On:

Boost off, no charge

source present

AE Active

AE pulsed high

725

875

150

—

725 (from cell)

875 (from cell)

150 (from cell)

AE and LCE Regulators

On: Boost off, no charge

source present

AE and LCE

Active

LCE pulsed high after AE

pulsed high

LCE Regulator On:

Boost off, no charge

source present

AE pulsed high, then LCE

pulsed high, then AE pulsed

low

LCE Active

�� Maxim Integrated Products

5

MAX17710

Energy-Harvesting Charger and Protector

Typical Operating Characteristics

(T = +25°C, unless otherwise noted.)

A

I

DD

vs. V

OVERTEMPERATURE

BATT

BOOST STARTUP

LCE AND AE AND SEL1 = GND

REGULATOR STARTUP

6

5

4

3

2

1

0

10

9

8

7

6

5

4

3

2

1

0

6

5

4

3

2

1

0

LX

T

A

= +85°C

CHG

SOLAR

AE

T

A

= +25°C

REG

PCKP

T

= -40°C

(V)

A

2

4

6

8

3.0

3.5

4.0

0

5

10

TIME (µs)

V

BATT

TIME (ms)

MEC101 CELL CHARGE PROFILE

2.5mW CHARGE SOURCE

I

vs. V

OVERTEMPERATURE

I

vs. V

OVERTEMPERATURE

DD

BATT

DD

BATT

LCE = VREG, AE, AND SEL1 = GND

AE = BATT, LCE, AND SEL1 = GND

MAX17710 toc06

825

775

725

675

625

575

525

4.15

4.10

4.05

4.00

3.95

3.90

3.85

3.80

3.75

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.05

0

190

170

150

130

110

90

I

BATT

T

= +85°C

= +25°C

A

T

= +85°C

= +25°C

A

V

BATT

T

A

= -40°C

T

= -40°C

3.5

A

3.0

3.5

4.0

3.0

4.0

0

50

100

150

200

250

V

(V)

V

(V)

BATT

TIME (Minutes)

BATT

BOOST CIRCUIT BREAK-EVEN

THRESHOLD vs. CELL VOLTAGE

(STANDARD APPLICATION CIRCUIT)

AE LOAD REGULATION

LCE LOAD REGULATION

3.5

3.3

3.1

2.9

2.7

2.5

2.3

2.1

1.9

1.7

1.5

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

3.5

3.3

3.1

2.9

2.7

2.5

2.3

2.1

1.9

1.7

1.5

0

50

100

150

200

3.5

3.6

3.7

3.8

3.9

4.0

4.1

0

50

100

LOAD (mA)

V

(V)

LOAD (µA)

BATT

�� Maxim Integrated Products

6

MAX17710

Energy-Harvesting Charger and Protector

Pin Configuration

TOP VIEW

+

1

2

3

4

5

6

BATT

CHG

FB

PCKP

LCE

12

11

10

9

REG

SEL1

SEL2

AE

MAX17710

GND

LX

8

EP

PGND

7

UTDFN

Pin Description

NAME

FUNCTION

1

BATT

Cell Input. Connect to the positive terminal of the cell without a bypass capacitor.

Charge Input. The IC charges the cell from the power source applied to this pin. Connect to the

output of the boost circuit or directly to a 4.21V or higher charge source.

2

3

CHG

FB

Boost Enable. The boost circuit is enabled by driving this pin above the FB

threshold. Afterwards,

ON

the boost circuit is disabled by driving this pin below FB

.

OFF

4

5

6

GND

LX

Device Ground. Connect to system ground.

Boost Input. Controls current drive through inductor of external boost circuit.

Power Ground. Connect to system ground.

PGND

Active Enable. Pulse high to enable high-power regulator output. Pulse low to disable regulator

output.

7

8

AE

Boost R

Select. Connect to system ground to select a boost R

of 0.5Ifor typical

DS-ON

SEL2

applications.

Regulator Voltage Select. Ground this pin to select a regulator output voltage of 2.3V, leave

disconnected for a regulator output voltage of 3.3V, or connect to the BATT pin for a regulator

output voltage 1.8V.

9

SEL1

10

11

REG

LCE

Regulator Output. Connect to load circuit. Bypass to system ground with a 1FF (typ) capacitor.

Low-Current Enable. Pulse high to enable the low-current regulator output after the high-current

regulator output is already active. Pulse low to disable.

Protected Output of Pack. Connect an external capacitor to PCKP to support energy buffering to

the load, especially in low-temperature applications (see Table 4). PCKP is used for pulsed current

storage.

12

—

PCKP

EP

Exposed Pad. Connect to GND.

�� Maxim Integrated Products

7

MAX17710

Energy-Harvesting Charger and Protector

Block Diagram

BATT

PCKP

UNREGULATED

OUTPUT

10µF

LINEAR CHARGE

AND IDEAL

DIODE CONTROL

OVERDISCHARGE

AND UNDERVOLTAGE

PROTECTION

THINERGY

MEC101

MAX17710

REF

CHG

0.1µF

RF, SOLAR,

OR OTHER

HIGH-VOLTAGE

SOURCE

LOAD V

1.0µF

DD

OUTPUT

LINEAR REG

REG

5.3V SHUNT

PROTECTION

TO REJECT

ZLLS410TA

3.3V/2.3V/1.8V

SELECT

OVERCHARGE

SEL 1

BATT

1.5µH

LX

PGND

SEL2

DISABLE

47µF

AE

EVENT

DETECTOR

TEG, SOLAR,

OR OTHER

LOW-VOLTAGE

SOURCE

MECHANICAL, RF,

PIEZO, OR OTHER

STATE

MACHINE

BOOST REG

300kI

LOAD V

DD

FB

ON

THRESHOLD

LCE

MICROCONTROLLER

FB

GND

�� Maxim Integrated Products

8

MAX17710

Energy-Harvesting Charger and Protector

remains active after the removal of the charge voltage.

The state of this latch is off when initial power is applied

Detailed Description

to the BATT pin.

Operation

The MAX177710 controls two main functions related to

While charging, the device consumes approximately

625nA from the CHG source until the voltage on CHG

exceeds 4.15V. Above 4.15V, the IC enters dropout and

BATT quiescent current increases from 1nA to 450nA.

management of an energy-harvesting application: charging

a low-capacity cell with overcharge protection and an LDO

regulator output with overdischarge protection. With the

exception of protection features, charging and regulation

functions operate completely independently of one another.

CHG Shunt

Whenever a harvest source pulls the CHG pin above

5.3V, an internal shunt regulator enables a path to GND

to limit the voltage at the CHG pin. The internal shunt

path can sustain currents up to 50mA. If it is possible for

the harvest source to exceed this power limit, an external

protection circuit is required to prevent damage to the

device. Figure 1 shows the typical application charge cir-

cuit harvesting from high-voltage charge sources. Note

that a 0.22FF on CHG is recommended for shunt stability

when charging from high-voltage sources.

Initial power-up of the device occurs when a cell is con-

nected to the BATT pin. In this state, the device pulls only

1nA (typ) from the cell and LDO functions are disabled. Only

after a charger has been applied and V

rises above

CHG

4.15V (V ) does the device initialize to full operation and

CE

allow discharging.

Charge-Regulator Operation

The device charges the cell from an external energy

source connected to the CHG pin. Whenever the volt-

age on CHG is greater than the voltage on BATT, the

energy-harvesting circuit directly passes current to the

cell without any interaction from the device. When CHG

In the application circuit example, the cell is charged by

several high-voltage harvest sources. Whenever either har-

vest source voltage is higher than the cell voltage, charge

is transferred directly. If either charge source exceeds

4.15V, the device begins to limit current flow to regulate the

cell’s voltage to 4.125V. If either charge source exceeds

5.3V, the internal CHG shunt discharges up to 50mA

through the device to GND to protect the CHG pin.

rises above V , the input linear regulator turns on to limit

CE

the charging voltage to 4.125V and protects the cell from

overcharge. Also at this time, any UVLO is reset, allow-

ing the LDO to power the application load. This release

of the lockout is latched by CHG exceeding V

and

CE

LOAD V

DD

THINERGY

MEC101

REG

AE

BATT

1µF

SEL2

EVENT

DETECTOR

SEL1

MECHANICAL,

RF, PIEZO,

OR OTHER

CHG

0.22µF

MAX17710

LOAD V

DD

HIGH-VOLTAGE AC

CHARGING SOURCE

(SOLAR, PIEZO)

HIGH-VOLTAGE DC

CHARGING SOURCE

(SOLAR, PIEZO)

LX

FB

MICROCONTROLLER

LCE

GND EP PGND PCKP

10µF

Figure 1. Typical Application Charge Circuit Harvesting from High-Voltage Charge Sources

�� Maxim Integrated Products

9

MAX17710

Energy-Harvesting Charger and Protector

driving FB below the FB

the boost circuit. The process repeats after the harvest

source capacitor is recharged.

threshold, which disables

Boost Regulator Operation

The device includes a simple boost regulator controller to

support energy harvesting from low-voltage solar or ther-

moelectric generator (TEG) devices. The boost converter

can harvest energy down to approximately 1FW when

operated in pulsed harvest mode and as high as 100mW

in continuous conversion. For a 0.8V harvest source and

a 4.1V cell, the device can deliver over 20mA (80mW), as

long as the harvest source can support it. Figure 2 shows

the typical application boost circuit boost harvesting

from a low-voltage solar-cell array.

OFF

Because the boost converter draws its quiescent current

directly from the cell (for startup reasons), it is important

to only enable the boost converter when it can provide

more power than the boost converter consumes from the

cell. This can be guaranteed as long as the capacitor

across the TEG is large enough to boost CHG above the

BATT pin. Note that it is important to use a high-speed

Schottky diode between LX and CHG to guarantee LX

does not exceed its absolute maximum voltage rating

during boost operation.

In the application circuit example, the solar cell array

charges the 47FF harvest-source capacitor until the volt-

age on FB exceeds the FB

threshold. At this time, the

ON

Charge Regulator Component Selection

External component selection depends on the charge

sources available to the device. Proper component

selection provides the highest efficiency operation of the

IC during energy harvesting. See Figure 2 as a reference.

This section describes component selection for boost

sources with operational voltages of 1.0V or high-voltage

sources. For boost charge sources with operational volt-

ages between 1.0V and 2.0V, additional components

are required. See the FB Divider section for a detailed

description.

LX pin is pulled low to force current through the external

inductor. LX begins to oscillate at a fixed 1.0MHz with

90% duty cycle. Each time LX is released by the device,

the external inductor forces the voltage of LX above CHG

and charges the 0.1FF CHG pin capacitor. When CHG

rises above the voltage of V

, charge is delivered to

BATT

the cell. If the CHG pin exceeds 4.5V during this time,

the boost converter enters a skip-mode operation to

limit voltage on CHG to 4.5V. Operation continues until

the voltage of the harvest-source capacitor collapses,

LOAD V

DD

THINERGY

MEC101

REG

BATT

SEL2

1µF

SEL1

CHG

EVENT

DETECTOR

0.1µF

AE

MECHANICAL,

RF, PIEZO,

OR OTHER

ZLLS410TA

HIGH-SPEED

SCHOTTKY

MAX17710

LOAD V

DD

1.5µH

LX

FB

47µF

SOLAR CELL 2

SOLAR CELL 1

300kI

MICROCONTROLLER

LCE

GND EP PGND PCKP

10µF

Figure 2. Typical Application Boost Circuit Boost Harvesting from a Low-Voltage Solar-Cell Array

�� Maxim Integrated Products 10

MAX17710

Energy-Harvesting Charger and Protector

CHG Capacitor

The CHG pin capacitor should be minimized to 0.1FF

for highest charge efficiency. However, when charging

from a high-voltage source, at least 0.22FF is required

for shunt stability.

This is the minimum size required for operation. Increasing

the size of the harvest source capacitor beyond this

level improves charge circuit efficiency at extremely low

input power (< 10FW), but care should be taken not to

increase the capacitor so large that the harvest source

cannot overcome the capacitor’s leakage. A maximum

value of 47FF is recommended.

LX Inductor

The LX pin inductor is not required for high-voltage

charge sources. For low-voltage sources, a minimum

inductor value of 0.68FH is required to prevent the maxi-

mum current rating of the LX pin from being exceeded.

Minimum inductor value is calculated as follows:

Table 2 lists boost converter external component values.

Minimum capacitor and inductor values are required for

proper operation of the charge circuit. Recommended

capacitor and inductor values provide optimum charge

efficiency. Components should be sized as close to

the recommended values that the application allows.

Component values below the minimum values, or above

the optimum values, are not recommended.

LX inductor = V

x t

/LX

= 1.0V x

FB-ON

BOOST-ON

IMAX

850ns/1A = 0.85FH

Boost Diode

The boost circuit diode must be a high-speed Schottky,

such as the ZLLS410TA from Diodes Incorporated. The

diode must turn on quickly to clamp the LX pin volt-

age rise at 6.0V or lower when the LX driver turns off.

The LX pin can be damaged if the maximum voltage is

exceeded.

FB Divider

Charge sources with operational voltages between 1.0V

and 2.0V require boosting, but are too high a voltage to

control the boost circuit efficiently. Under these condi-

tions, a voltage-divider is required to lower the voltage

seen by the FB pin (see Figure 3). The divider formed by

R1 and R2 allows the voltage on the FB pin to transition

Harvest Source Capacitor

The harvest source capacitor must be a minimum of 70

times larger than the CHG pin capacitor to boost the

charge pin to the maximum charge voltage under worst-

case conditions:

properly between the FB

boosting. The value for R2 is calculated as follows:

and FB

thresholds during

ON

OFF

V

= F

x (R1 + R2)/R1

HARVEST-ON

BON

R2 = (V

- 1.0V) x 500kI

HARVEST-ON

Source capacitor = (4.125V)²/(0.485V)²x

CHG capacitor

where V

harvest source.

is the operational voltage of the

HARVEST-ON

Table 2. Boost Converter External Component Values

CHG

CAPACITOR

(µF)

MINIMUM LX

INDUCTOR

(µH)

RECOMMENDED

LX INDUCTOR

(µH)

MINIMUM

HARVEST SOURCE

CAPACITOR (µF)

RECOMMENDED

HARVEST SOURCE

CAPACITOR (µF)

APPLICATION

CHARGE SOURCE

High voltage

0.22

0.1

N/A

0.85

N/A

1.5

N/A

7.0

N/A

47

Low voltage < 10FW

Low voltage > 10FW

0.1

7.0

High voltage and low

voltage < 10FW

0.22

0.85

1.5

15.4

47

High voltage and low

voltage > 10FW

15.4

�� Maxim Integrated Products 11

MAX17710

Energy-Harvesting Charger and Protector

The C1 1nF capacitor acts as a voltage-level feed for-

ward to increase the responsiveness of the divider circuit

as the harvest source capacitor is discharged. The mini-

mum voltage is defined as:

CHG

0.1µF

V

~= V

- (FB

- FB

)

HARVEST-OFF

HARVEST-ON

ON

OFF

ZLLS410TA

L1

V

~= V

- 0.5V (typ)

HARVEST-OFF

HARVEST-ON

MAX17710

where V

source capacitor during boost.

is the lowest voltage of the harvest

HARVEST-OFF

1.0V TO 2.0V

CHARGE

SOURCE

LX

FB

Because of the divider on the FB pin, the voltage seen by

the LX pin inductor is higher than the typical circuit. The

inductor must be resized so that the LX pin current limits

are not exceeded:

C1

1nF

R2

47µF

LX Inductor = V

V

x t

/LX

=

HARVEST-ON

BOOST-ON

IMAX

R1

500kI

x (8.5 x 10^-7)

All other components are selected as normal.

Energy-Harvesting Design Approaches

When designing an optimal energy harvest system,

there are three types of design approaches: linear har-

vest, boost harvest, and maximum-power-point tracking

(MPPT). In harvesting applications, it is very critical to

not discharge the cell when charging is failing. When

the harvesting power is low enough, eventually the sys-

tem discharges the cell rather than charges. This is the

break-even point of the harvester. For linear harvesting,

this break-even point is lower because the required

quiescent current is less. However, for boost harvesting,

the breakeven threshold is 1FA. While an MPPT system

can utilize the harvesting source more intelligently in

high-power situations, it inevitably results in higher qui-

escent current and a poorer break-even threshold. MPPT

systems must measure the current and voltage, multiply

to determine power, and make decisions to improve the

power. These required measurements automatically

significantly increase the quiescent current budget

by tens of µA. Figure 4 shows energy-harvesting modes

of operation vs. charge efficiency.

Figure 3. FB Divider Circuit to Improve Boost Efficiency for

Charge Sources Between 1.0V and 2.0V

MPPT

(MAX POWER

TRACKING)

BOOST HARVEST

LINEAR

HARVEST

BREAK-EVEN

THRESHOLDS

LDO Output Operation

The device regulates voltage from the cell to a load

circuit on the REG pin through an LDO regulator. The

regulator can be configured for 3.3V, 2.3V, or 1.8V opera-

tion. The LDO supports loads up to 75mA (high-current

mode). For lighter load applications, a low-power mode

of operation reduces the quiescent current drain on the

cell. A UVLO circuit prevents the regulator from start-

ing up or disabling the regulator when active if the cell

becomes overdischarged.

POWER FROM HARVEST SOURCE

Figure 4. Energy-Harvesting Modes of Operation vs. Charge

Efficiency

�� Maxim Integrated Products 12

MAX17710

Energy-Harvesting Charger and Protector

The LDO becomes active when the AE pin is pulsed

open or pulled to REG, and returns to shutdown mode

when LCE is driven below its logic-low threshold. Figure

5 is the regulator output state diagram.

above or held above its logic-high threshold, but the

regulator output is not immediately enabled. The device

first charges the external capacitor on PCKP. When the

voltage level on PCKP reaches 3.7V, the regulator output

is enabled in high-current mode. Powering the LDO from

PCKP instead of directly from the cell allows the device

to support large surge or startup inrush currents from the

load that the cell would be unable to handle directly.

Cell Undervoltage Lockout (UVLO)

If the cell and PCKP capacitance cannot provide sus-

tained support for the load, then the voltage at PCKP col-

lapses. When PCKP collapses, the system load typically

stops and allows the PCKP voltage to recover, resulting

in a perpetual retry in a futile attempt to support a load

that cannot be supported. When PCKP fails in this way,

the device shuts off the REG output to prevent futile load

retries and protect the cell from overdischarge. When the

REG output is latched off, the BATT quiescent current

reduces to 1nA (typ). Once UVLO occurs, the regulator

output remains disabled until the device detects that a

Once in high-current mode, the AE pin can remain logic-

high or transition to an open state, and the ouput remains

active. The LDO returns to shutdown only when the AE

pin is driven below its logic-low threshold. Alternatively,

the LDO is transitioned to low-current mode by pulsing

or holding the LCE to the REG pin voltage, followed by

pulsing or holding the AE pin logic-low. Note that the reg-

ulator transitions through a state where both high-current

and low-current modes are active at the same time. While

in low-current mode, the quiescent current drain of the

cell is reduced to 150nA, while the maximum load current

able to be supplied becomes 50FA. Similar to the AE pin

operation, the regulator remains active if the LCE pin is

charge source has been connected to the system (V

> 4.15V). Figure 6 shows the UVLO protection modes.

CHG

Connecting any load to REG or PCKP instead of connect-

ing directly to the cell is highly recommended. This con-

trols the quiescent current during shutdown, enables the

device to support startup during cold, and also protects

the cell from overdischarge.

LCE PULSED LOW

SHUTDOWN

PCKP OFF

REG OFF

AE PULSED LOW

I

= 1nA (typ)

QBATT

AE PULSED HIGH

LCE PULSED

HIGH

AE PULSED

LOW

STARTUP

SUCCESS

> 3.7V

STARTUP

AE REGULATOR

ACTIVE

AE AND LCE

REGULATORS ACTIVE

LCE REGULATOR

ACTIVE

PCKP ON

REG OFF

= PCKP CAPACITOR

CHARGE CURRENT

+ 725nA (typ)

V

PCKP

CHARGE

DETECTED

LCE PULSED

LOW

AE PULSED

HIGH

PCKP ON

REG ON

PCKP ON

REG ON

PCKP ON

REG ON

I

QBATT

VCHG > VCE

I

= 725nA (typ)

I

= 875nA (typ)

I

= 150nA (typ)

QBATT

STARTUP FAIL

< 2.15V

CELL UNDERVOLTAGE

V

PCKP

V

< 2.15V (HIGH-CURRENT MODE)

< 3.0V (LOW-CURRENT MODE)

AFTER 500µs

AFTER 5s

PCKP

UNDERVOLTAGE

LOCKOUT

PCKP OFF

REG OFF

I

= 1nA (typ)

QBATT

POWER-ON RESET (POR)

Figure 5. Regulator Output State Diagram

�� Maxim Integrated Products 13

MAX17710

Energy-Harvesting Charger and Protector

4.1V

2.15V

0V

BATT

PCKP

4.1V

2.15V

0V

BATT

4.1V

0V

4.1V

3.7V

PCKP

AE

0V

V

OH-AE

V

OH-AE

AE

V

OL-AE

V

OL-AE

3.3V

0V

REG

UVLO

0V

> t

UVLO1

(5s typ)

a. NORMAL REGULATOR OUTPUT ENABLE SEQUENCE

b. REGULATOR OUTPUT ENABLE FAIL DUE TO UVLO TIMEOUT

4.1V

BATT

PCKP

2.15V

0V

4.1V

3.0V

BATT

PCKP

4.1V

0V

2.15V

0V

3.3V

0V

3.3V

0V

REG

> t

UVLO2

(500µs typ)

4.1V

0V

UVLO

0V

UVLO

c. HIGH-CURRENT MODE REGULATOR OUTPUT DISABLED DUE TO UVLO TIMEOUT

d. LOW-CURRENT MODE REGULATOR OUTPUT DISABLED DUE TO UVLO DETECTION

Figure 6. ULVO Protection Modes

�� Maxim Integrated Products 14

MAX17710

Energy-Harvesting Charger and Protector

Regulator Voltage Selection

The SEL1 pin selects at which voltage REG operates.

Connect SEL1 to BATT for 1.8V operation, three-state for

3.3V operation, or connect to GND for 2.3V operation.

Note that the voltage regulation value is latched when

enabled. To change the regulation voltage point, the reg-

ulator must be disabled and then reenabled. See Table 3.

addition to voltage protection, the ramp of the PCKP

switch impedance is changed slowly (5ms to full on) to

gradually load the cell and not collapse the voltage on a

room-temperature cell. Because of these protection fea-

tures, an application can now support brief high-current

pulses by including a large capacitance at PCKP. This

allows support for pulse loads many times higher than

that naturally supported by the cell alone.

PCKP Pin Capacitor Selection

There are several cases when the system might overload

the cell, potentially causing damage. They are prevented

with the PCKP load switch block and external capacitor:

A large PCKP capacitance can be selected to support

a pulse load even while the cell is very cold, and would

normally be incapable of supporting a significant load.

Choose this capacitor according to Table 4 or the follow-

ing equation:

U During startup, when there is an inrush current due to

the application’s load and capacitance.

C

PCKP

= I

x t

/(3.7 - V

)

TASK

MIN

U When the cell is cold (such as -40NC), and due to

increased cell resistance, it is unable to support high-

load currents.

where:

I

t

is the current required to sustain a required task,

TASK

is the time duration of the task, and V

is the

U If the system requires a load current higher than can be

supported by the cell alone.

MIN

minimum voltage of the load doing the task.

This equation assumes that the BATT impedance is high

and cannot support the load.

The device provides cell undervoltage protection by

limiting the current from BATT to PCKP and guarantee-

ing that the cell voltage does not fall below 2.15V. In

Table 3. Regulator Output Voltage Selection

SEL1 PIN CONNECTION

Connect to BATT

Open circuit

REG PIN OUTPUT VOLTAGE (V)

1.8

3.3

2.3

Connect to GND

Table 4. PCKP Pin Capacitor Values by Application

V

t

(ms)

I

(mA)

C

(µF)*

MIN

TASK

PCKP

3.0

2.8

2.3

5

8

100

5

4

5

50

28

14

18

36

2.5

5

10

*Capacitance value tolerances need to be considered.

�� Maxim Integrated Products 15

MAX17710

Energy-Harvesting Charger and Protector

Package Information

Ordering Information

For the latest package outline information and land patterns

(footprints), go to www.maxim-ic.com/packages. Note that a

“+”, “#”, or “-” in the package code indicates RoHS status only.

Package drawings may show a different suffix character, but

the drawing pertains to the package regardless of RoHS status.

PART

TEMP RANGE

-40NC to +85NC

PIN-PACKAGE

12 UTDFN-EP*

MAX17710G+U

MAX17710G+T

+Denotes a lead(Pb)-free/RoHS-compliant package.

U = Signifies tape cut.

T = Tape and reel.

PACKAGE

TYPE

PACKAGE OUTLINE

LAND

PATTERN NO.

CODE

NO.

*EP = Exposed pad.

12 UTDFN-EP V1233N+1

21-0451

90-0339

�� Maxim Integrated Products 16

MAX17710

Energy-Harvesting Charger and Protector

Revision History

REVISION

NUMBER

REVISION

DATE

PAGES

CHANGED

DESCRIPTION

0

6/11

Initial release

—

Corrections and clarifications made based on customer feedback; added

new TOC #9 and updated two EC table limits

1

7/11

3–7, 9, 10, 12–15

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.

Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical

Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

17

©

2011 Maxim Integrated Products

Maxim is a registered trademark of Maxim Integrated Products, Inc.


型号：	MAX17710_1107
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	Energy-Harvesting Charger and Protector 能量收集充电器和保护
文件：	总17页 (文件大小：1395K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

MAX17710_1107 [MAXIM]

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