MAXIM MAX668, MAX669 User Manual

General Description

The MAX668/MAX669 constant-frequency, pulse-width­modulating (PWM), current-mode DC-DC controllers are
designed for a wide range of DC-DC conversion applica­tions including step-up, SEPIC, flyback, and isolated­output configurations. Power levels of 20W or more can
be controlled with conversion efficiencies of over 90%.
The 1.8V to 28V input voltage range supports a wide
range of battery and AC-powered inputs. An advanced
BiCMOS design features low operating current (220µA),
adjustable operating frequency (100kHz to 500kHz),
soft-start, and a SYNC input allowing the MAX668/
MAX669 oscillator to be locked to an external clock.

DC-DC conversion efficiency is optimized with a low
100mV current-sense voltage as well as with Maxim’s
proprietary Idle Mode™ control scheme. The controller
operates in PWM mode at medium and heavy loads for
lowest noise and optimum efficiency, then pulses only as
needed (with reduced inductor current) to reduce oper­ating current and maximize efficiency under light loads.
A logic-level shutdown input is also included, reducing
supply current to 3.5µA.

The MAX669, optimized for low input voltages with a
guaranteed start-up voltage of 1.8V, requires boot­strapped operation (IC powered from boosted output). It
supports output voltages up to 28V. The MAX668 oper­ates with inputs as low as 3V and can be connected in
either a bootstrapped or non-bootstrapped (IC powered
from input supply or other source) configuration. When
not bootstrapped, it has no restriction on output voltage.
Both ICs are available in an extremely compact 10-pin
µMAX package.

Features

o 1.8V Minimum Start-Up Voltage (MAX669)
o Wide Input Voltage Range (1.8V to 28V)
o Tiny 10-Pin µMAX Package
o Current-Mode PWM and Idle Mode™ Operation
o Efficiency over 90%
o Adjustable 100kHz to 500kHz Oscillator or

SYNC Input

o 220µA Quiescent Current
o Logic-Level Shutdown
o Soft-Start

Applications

Cellular Telephones

Telecom Hardware

LANs and Network Systems

POS Systems

MAX668/MAX669

1.8V to 28V Input, PWM Step-Up
Controllers in µMAX

________________________________________________________________

Maxim Integrated Products

1

19-4778; Rev 2; 1/12

Idle Mode is a trademark of Maxim Integrated Products.
+ Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
/V Denotes an automotive qualified part.
Note: Devices are also available in a lead(Pb)-free/RoHS-com­pliant package. Specify lead-free by adding “+” to the part
number when ordering.

Ordering Information

Typical Operating Circuit

Pin Configuration

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.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE PIN - PA C K A G E

MAX668EUB -40°C to +85°C 10 µMAX

MAX669EUB -40°C to +85°C 10 µMAX

MAX669EUB/V+T -40°C to +85°C 10 µMAX

= 1.8V to 28V

V

IN

TOP VIEW

= 28V

V

V

CC

SYNC/
SHDN

FREQ

MAX669

LDO

REF

EXT

CS+

PGND

FB

GND

OUT

LDO

FREQ

GND

1

2

MAX668

3

MAX669

4

5

µMAX

10

9

8

7

6

SYNC/SHDN

V

CC

EXT

PGNDREF

CS+FB

MAX668/MAX669

1.8V to 28V Input, PWM Step-Up
Controllers in µMAX

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= V

LDO

= +5V, R

OSC

= 200kΩ, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

V

CC

to GND ..........................................................-0.3V to +30V

PGND to GND....................................................................±0.3V

SYNC/SHDN to GND .............................................-0.3V to +30V

EXT, REF to GND.....................................-0.3V to (V

LDO

+ 0.3V)

LDO, FREQ, FB, CS+ to GND ................................ -0.3V to +6V

LDO Output Current...........................................-1mA to +20mA

REF Output Current..............................................-1mA to +1mA

LDO Short Circuit to GND .........................................Momentary

REF Short Circuit to GND ..........................................Continuous

Continuous Power Dissipation (T

A

= +70°C)

10-Pin µMAX (derate 5.6mW/°C above +70°C) ............444mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering,10sec) ..............................+300°C

Soldering Temperature (Reflow) ......................................+300°C

Lead(Pb)-Free Packages..............................................+260°C

Packages Containing Lead(Pb)....................................+240°C

85 100 115

425 500 575

225 250 275R

OSC

= 200kΩ ±1%

Oscillator Frequency

Oscillator

1.0 1.1 1.2Rising edge, 1% hysteresisREF Undervoltage Lockout Threshold

-2 -10REF load = 0 to 50µA REF Load Regulation

1.225 1.250 1.275No load, C

REF

= 0.22µFREF Output Voltage

2.40 2.50 2.60

Sensed at LDO, falling edge,
hysteresis = 1%, MAX668 only

Undervoltage Lockout Threshold

2.65 5.50

3V ≤ VCC≤ 28V
(includes LDO dropout)

4.50 5.00 5.50

LDO Output Voltage

Reference and LDO Regulators

328MAX668

PWM Controller

Input Voltage Range, V

CC

3.5 6

SYNC/SHDN = GND, VCC= 28V

Shutdown Supply Current (VCC)

220 350VFB= 1.30V, VCC= 3V to 28VVCCSupply Current (Note 1)

0.2 1CS+ forced to GNDCS+ Input Current

51525Idle Mode Current-Sense Threshold

2.7 5.5Input Voltage Range with VCCTied to LDO

1.225 1.250 1.275FB Threshold

1 20 VFB= 1.30VFB Input Current

85 100 115Current Limit Threshold

MIN TYP MAXCONDITIONSPARAMETER

kHz

V

mV

V

V

V

µA

µA

µA

mV

mV

nA

V

V

V

UNITS

MAX669 1.8 28

LDO load =
∞ to 400Ω

5V ≤ VCC≤ 28V
(includes LDO dropout)

R

OSC

= 500kΩ ±1%

R

OSC

= 100kΩ ±1%

0.013

Typically 0.013% per mV on CS+;
VCS+ range is 0 to 100mV for 0 to full
load current.

FB Threshold Load Regulation %/mV

0.012

Typically 0.012% per % duty factor on
EXT; EXT duty factor for a step-up is:
100% (1 – V

IN/VOUT

)

FB Threshold Line Regulation %/%

REFERENCE AND LDO REGULATORS

OSCILLATOR

PWM CONTROLLER

V

MAX668/MAX669

1.8V to 28V Input, PWM Step-Up
Controllers in µMAX

_______________________________________________________________________________________ 3

70

100 500SYNC Input Frequency Range

SYNC/SHDN Falling Edge to Shutdown Delay

2 5 EXT high or lowEXT On-Resistance

1EXT forced to 2V

Ω

EXT Sink/Source Current

1.51.8V < V

CC

< 3.0V (MAX669)

A

SYNC/SHDN Input High Voltage

0.301.8V < V

CC

< 3.0V (MAX669)

µA

SYNC/SHDN Input Low Voltage

0.5 3.0V

SYNC/SHDN

= 5V

SYNC/SHDN Input Current

1.5 6.5V

SYNC/SHDN

= 28V

V

MIN TYP MAXCONDITIONSPARAMETER

µs

kHz

UNITS

ELECTRICAL CHARACTERISTICS (continued)

(VCC= V

LDO

= +5V, R

OSC

= 200kΩ, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

ELECTRICAL CHARACTERISTICS

(VCC= V

LDO

= +5V, R

OSC

= 200kΩ, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)

2.40 2.60

Sensed at LDO, falling edge,
hysteresis = 1%, MAX669 only

LDO Undervoltage Lockout Threshold

2.65 5.50

3V ≤ VCC≤ 28V
(includes LDO dropout)

4.50 5.50

5V ≤ VCC≤ 28V
(includes LDO dropout)

LDO Output Voltage

Reference and LDO Regulators

V

328MAX668

V

PWM Controller

Input Voltage Range, V

CC

6

SYNC/SHDN = GND, VCC= 28V

Shutdown Supply Current (VCC)

350VFB= 1.30V, VCC= 3V to 28V

µA

VCCSupply Current (Note 1)

1CS+ forced to GND

µA

CS+ Input Current

327

µA

Idle Mode Current-Sense Threshold

2.7 5.5

mV

Input Voltage Range with VCCTied to LDO

1.22 1.28

mV

FB Threshold

20 VFB= 1.30V nAFB Input Current

85 115

V

Current-Limit Threshold

MIN MAXCONDITIONS

V

PARAMETER

V

UNITS

86 90 94R

OSC

= 500kΩ ±1%

MAX669

LDO load =
∞ to 400Ω

1.8 28

3.0V < V

CC

< 28V

3.0V < V

CC

< 28V 2.0

0.45

V

200

Not testedSYNC Input Rise/Fall Time ns

50 200Minimum SYNC Input Low Pulse Width ns

20 45Minimum SYNC Input-Pulse Duty Cycle %

290Minimum EXT Pulse Width ns

87 90 93R

OSC

= 200kΩ ±1%

86 90 94R

OSC

= 100kΩ ±1%Maximum Duty Cycle %

PWM CONTROLLER

REFERENCE AND LDO REGULATORS

MAX668/MAX669

1.8V to 28V Input, PWM Step-Up
Controllers in µMAX

4 _______________________________________________________________________________________

ns

%Minimum SYNC Input-Pulse Duty Cycle 45

Minimum SYNC Input Low Pulse Width 200

SYNC Input Rise/Fall Time Not tested 200 ns

ELECTRICAL CHARACTERISTICS (continued)

(VCC= V

LDO

= +5V, R

OSC

= 200kΩ, TA= -40°C to +85°C, unless otherwise noted.)

R

OSC

= 200kΩ ±1% 87 93

SYNC Input Frequency Range 100 500 kHz

1.8V < V

CC

< 3.0V (MAX669) 0.30

V

1.8V < V

CC

< 3.0V (MAX669) 1.5

V

V

SYNC/SHDN

= 28V 6.5

µA

EXT On-Resistance EXT high or low 5 Ω

SYNC/SHDN Input Current

V

SYNC/SHDN

= 5V 3.0

Note 1: This is the VCCcurrent consumed when active but not switching. Does not include gate-drive current.
Note 2: Limits at T

A

= -40°C are guaranteed by design.

222 278

UNITSPARAMETER CONDITIONS MIN MAX

R

OSC

= 200kΩ ±1%

%Maximum Duty Cycle

R

OSC

= 500kΩ ±1% 86 94

425 575R

OSC

=100kΩ ±1%

kHzOscillator Frequency

85 115R

OSC

= 500kΩ ±1%

R

OSC

= 100kΩ ±1% 86 94

SYNC/SHDN Input High Voltage

3.0V < V

CC

< 28V 2.0

SYNC/SHDN Input Low Voltage

3.0V < V

CC

< 28V 0.45

VREF Output Voltage No load, C

REF

= 0.22µF 1.22 1.28

mVREF Load Regulation REF load = 0 to 50µA -10

VREF Undervoltage Lockout Threshold Rising edge, 1% hysteresis 1.0 1.2

OSCILLATOR

MAX668/MAX669

1.8V to 28V Input, PWM Step-Up
Controllers in µMAX

_______________________________________________________________________________________

5

Typical Operating Characteristics

(Circuits of Figures 2, 3, 4, and 5; TA= +25°C; unless otherwise noted.)

EFFICIENCY vs. LOAD CURRENT

(V

= 5V)

95

90

VIN = 3.3V

85

80

75

70

EFFICIENCY (%)

65

60

BOOTSTRAPPED
FIGURE 3

55

R4 = 200kΩ

50

1 10 100 1000 10,000

OUT

VIN = 3.6V

VIN = 2.7V

VIN = 2V

LOAD CURRENT (mA)

MAX669 MINIMUM START-UP VOLTAGE

vs. LOAD CURRENT

3.0

V

= 5V

OUT

2.5

2.0
V

= 12V

1.5

1.0

MINIMUM START-UP VOLTAGE (V)

0.5

BOOTSTRAPPED
FIGURE 2

0

0 400300100 200 500 600 700 800 900 1000

LOAD CURRENT (mA)

OUT

MAX668 toc01

MAX668 toc04

95

90

85

80

EFFICIENCY (%)

75

70

1200

1000

800

600

400

SUPPLY CURRENT (µA)

200

0

MAX668 EFFICIENCY vs.

LOAD CURRENT (V

VIN = 5V
NON-BOOTSTRAPPED
FIGURE 4
R4 = 200kΩ

1 10,000100010 100

LOAD CURRENT (mA)

SUPPLY CURRENT vs.

SUPPLY VOLTAGE

CURRENT INTO VCC PIN
R

OSC

MAX669

MAX668

010155 202530

SUPPLY VOLTAGE (V)

MAX668 EFFICIENCY vs.

LOAD CURRENT (V

VIN = 12V

VIN = 5V

NON-BOOTSTRAPPED
FIGURE 4
R4 = 200kΩ

1 10,000100010 100

LOAD CURRENT (mA)

OUT

= 24V)

VIN = 8V

NO-LOAD SUPPLY CURRENT vs.

SUPPLY VOLTAGE

V

= 12V

OUT

BOOTSTRAPPED
FIGURE 2
R4 = 200kΩ

0

042681012

SUPPLY VOLTAGE (V)

OUT

= 500kΩ

= 12V)

MAX668 toc02

MAX668 toc05

95

90

85

80

EFFICIENCY (%)

75

70

4000

3500

3000

2500

2000

1500

1000

NO-LOAD SUPPLY CURRENT (µA)

500

MAX668 toc03

MAX668 toc06

SHUTDOWN CURRENT vs.

SUPPLY VOLTAGE

3.5

MAX669

3.0

2.5

2.0

1.5

1.0

SHUTDOWN CURRENT (µA)

0.5

0

0105 15202530

MAX668

CURRENT INTO VCC PIN

SUPPLY VOLTAGE (V)

MAX668 toc07

SUPPLY CURRENT vs.

TEMPERATURE

290

270

R

= 100kΩ

250

230

210

SUPPLY CURRENT (µA)

190

170

150

-40-20 0 20406080100
TEMPERATURE (°C)

OSC

R

R

OSC

OSC

= 200kΩ

= 500kΩ

300

MAX668 toc08

250

200

150

100

LDO DROPOUT VOLTAGE (mV)

50

0

0.1 1 10 20

LDO DROPOUT VOLTAGE vs.

LDO CURRENT

MAX668 toc09

VIN = 3V

VIN = 4.5V

LDO CURRENT (mA)

MAX668/MAX669

1.8V to 28V Input, PWM Step-Up
Controllers in µMAX

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Circuits of Figures 2, 3, 4, and 5; TA= +25°C; unless otherwise noted.)

1.240

1.242

1.243

1.241

1.245

1.246

1.244

1.248

1.249

1.247

1.250

-40-20 0 20406080100

REFERENCE VOLTAGE vs.

TEMPERATURE

MAX668 toc10

TEMPERATURE (°C)

REFERENCE VOLTAGE (V)

VCC = 5V

0

100

150

50

250

300

200

400

450

350

500

0 100 200 300 400 500

SWITCHING FREQUENCY vs. R

OSC

MAX668 toc11

R

OSC

(kΩ)

SWITCHING FREQUENCY (kHz)

VCC = 5V

0

100

300

400

500

600

-40 0-20 20406080100

SWITCHING FREQUENCY vs.

TEMPERATURE

MAX668 toc12

TEMPERATURE (°C)

SWITCHING FREQUENCY (kHz)

200

100kΩ

165kΩ

499kΩ

VIN = 5V

100 1000 10,000

EXT RISE/FALL TIME vs.

CAPACITANCE

MAX668 toc13

CAPACITANCE (pF)

EXT RISE/FALL TIME (ns)

60

0

10

20

30

40

50

tR, VCC = 3.3V

tF, VCC = 3.3V

tR, VCC = 5V

tF, VCC = 5V