MAXIM MAX1709 User Manual

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

General Description

The MAX1709 sets a new standard of space savings for
high-power, step-up DC-DC conversion. It delivers up
to 20W at a fixed (3.3V or 5V) or adjustable (2.5V to

5.5V) output, using an on-chip power MOSFET from a
+0.7V to +5V supply.

Fixed-frequency PWM operation ensures that the
switching noise spectrum is constrained to the 600kHz
fundamental and its harmonics, allowing easy postfilter­ing for noise reduction. External clock synchronization
capability allows for even tighter noise spectrum con­trol. Quiescent power consumption is less than 1mW to
extend operating time in battery-powered systems.

Two control inputs (ONA, ONB) allow simple push-on,
push-off control through a single momentary pushbut­ton switch, as well as conventional on/off logic control.
The MAX1709 also features programmable soft-start
and current limit for design flexibility and optimum per­formance with batteries.

The MAX1709 is supplied in both a high-power TSSOP
package, which allows a 10A

RMS

switch current and a

4A output, and a narrow SO package, which supplies a

2.4A output with a switch rated at 6A

RMS

. Although the
narrow SO device has a lower RMS switch rating, it has
the same peak switch current rating as the TSSOP
device, and so can supply 4A loads intermittently. If
loads of 2A or less are required, refer to the MAX1708.

________________________Applications

Routers, Servers, Workstations, Card Racks

Local 2.5V to 3.3V or 5V Conversion

Local 3.3V to 5V Conversion

3.6V or 5V RF PAs in Communications Handsets

Features

♦ On-Chip 10A Power MOSFET

♦ 5V, 4A Output from a 3.3V Input

♦ Fixed 3.3V or 5V Output Voltage or

Adjustable (2.5V to 5.5V)

♦ Input Voltage Range Down to 0.7V

♦ Low Power Consumption

1mW Quiescent Power
1µA Current in Shutdown Mode

♦ Low-Noise, Constant Frequency Operation

(600kHz)

♦ Synchronizable Switching Frequency

(350kHz to 1000kHz)

MAX1709

4A, Low-Noise, High-Frequency,

Step-Up DC-DC Converter

________________________________________________________________ Maxim Integrated Products 1

Pin Configurations

ONA

REF

SS/LIM

CLK

OUTPUT

3.3V, 5V,
OR ADJ
UP TO 4A

OUT

GND

LX

1μH

OFF

ON

INPUT

1V TO 5V

SYNC

OR

INTERNAL

MAX1709

Typical Operating Circuit

19-1724; Rev 1; 7/05

EVALUATION KIT

AVAILABLE

Ordering Informations

PART

PIN-PACKAGE

MAX1709ESE -40°C to +85°C 16 Narrow SO

MAX1709EUI+ -40°C to +85°C 28 TSSOP-EP*

+Indicates lead-free package.

*Exposed pad.

Pin Configurations continued at end of data sheet.

TEMP RANGE

TOP VIEW

1

ONA

2

LX

3

LX

4

MAX1709

5

LX

6

LX

7

LX

TSSOP-EP*

ONB

28

CLK

27

26

3.3/5

NCLX

25

24

NC

23

PGND

22

PGNDLX

218 PGND

209 PGNDNC

1910 PGNDNC

1811 PGNDGND

1712 NCSS/ILM

1613 FBREF

1514 OUTGND

MAX1709

4A, Low-Noise, High-Frequency,
Step-Up DC-DC Converter

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

OUT

= V

CLK

= +3.6V, ONA = ONB = FB = GND, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

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

ONA, ONB, OUT, SS/LIM, 3.3/5 to GND ...............-0.3V to +6.0V

LX to PGND ...........................................................-0.3V to +6.0V

FB, CLK, REF to GND.............................. -0.3V to (V

OUT

+ 0.3V)

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

Continuous Power Dissipation (T

A

= +70°C)

16-Pin Narrow SO (derate 16.5mW/°C above +70°C) .....1.3W

28-Pin TSSOP Exposed Pad

(derate 23.8mW/°C above +70°C)...................................1.9W

28-Pin TSSOP Exposed Pad Junction-to-Exposed

Pad Thermal Resistance......................................……1.2°C/W

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

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

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

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

PARAMETER CONDITIONS MIN TYP

MAX

UNITS

3.3/5 = GND, I

SW

= 1A 3.26 3.34 3.42

Output Voltage VFB < 0.1V (Note 1)

3.3/5 = OUT, I

SW

= 1A 4.92 5.05 5.17

V

Load Regulation Measured between 1A < ISW < 3A (Note 2)

%/A

FB Regulation Voltage ISW = 1A

V

FB Input Current V

FB

= +1.5V

1

200 nA

Output Voltage Adjust Range 2.5 5.5 V

Output Undervoltage Lockout (Note 3) 2.0 2.3 V

Frequency in Startup Mode V

OUT

=1.5V 40 400 kHz

Minimum Startup Voltage I

OUT

< 1mA (Note 1), TA = +25°C (Note 4) 0.9 1.1 V

Minimum Operating Voltage (Note 5) 0.7 V

Soft-Start Pin Current V

SS/LIM

= 1V 3.2 4 5.0 µA

OUT Supply Current VFB = 1.5V (Note 6) 200 440 µA

OUT Leakage Current In
Shutdown

V

ONB

= 3.6V 0.1 5 µA

LX Leakage Current VLX = V

ONB

= V

OUT

= +5.5V 0.1 40 µA

n-Channel Switch
On-Resistance

22 40 mΩ

SS/LIM = open

7.5

9

12

n-Channel Current Limit

SS/LIM = 150kΩ to GND

3.5

5

6.5

A

MAX1709EUI+ 10

RMS Switch Current

MAX1709ESE 6

A

RMS

Reference Voltage I

REF

= 0

V

Reference Load Regulation -1µA < I

REF

< 50µA 4 10 mV

Reference Supply Rejection +2.5V < V

OUT

< +5.5V 0.2 5 mV

ONA, ONB, 3.3/5, 1.2V < V

OUT

< 5.5V

Input Low Level (Note 7)

CLK, 2.7V < V

OUT

< 5.5V

V

-0.25 -0.45

1.215 1.240 1.265

1.245 1.260 1.275

0.2 ×

V

OUT

0.2 ×

V

OUT

MAX1709

4A, Low-Noise, High-Frequency,

Step-Up DC-DC Converter

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

OUT

= V

CLK

= +3.6V, ONA = ONB = FB = GND, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

ELECTRICAL CHARACTERISTICS

(V

OUT

= V

CLK

= +3.6V, ONA = ONB = FB = GND, TA= -40°C to +85°C, unless otherwise noted.) (Note 9)

PARAMETER CONDITIONS MIN TYP

MAX

UNITS

ONA, ONB, 3.3/5, 1.2V < V

OUT

<5.5

Input High Level

CLK, 2.7 V< V

OUT

< 5.5V

V

Logic Input Current ONA, ONB, CLK, 3.3/5 1 µA

Internal Oscillator Frequency 520 600 680 kHz

Maximum Duty Cycle 82 90 94 %

External Clock Frequency
Range

350

kHz

CLK Pulse Width (Note 8) 100 ns

CLK Rise/Fall Time (Note 8) 50 ns

0.8 × V

OUT

0.8 × V

OUT

1000

Output Voltage

FB Regulation Voltage I

FB Input Current V

Load Regulation Measured between 1A < ISW < 5A (Note 2) -0.45 %/A

Soft-Start Pin Current SS/LIM = 1V 3.2 5.2 µA

OUT Leakage Current in
Shutdown

OUT Supply Current V

n-Channel Switch
On-Resistance

n-Channel Current Limit

Reference Voltage I

PARAMETER CONDITIONS MIN TYP MAX UNITS

VFB < 0.1V, V

(Note 1) 3.3/5 = OUT, I

= 1A 1.21 1.27 V

SW

= +1.5V 200 nA

FB

V

= 3.6V 5 µA

ONB

= 1.5V (Note 6) 400 µA

FB

SS/LIM = unconnected 7.5 15
SS/LIM = 150kΩ to GND 3.5 7

= 0 1.24 1.28 V

REF

= +2.4V 3.3/5 = GND, I

IN

= 1A 3.24 3.45

SW

= 1A 4.9 5.2

SW

V

40 mΩ

V

Note 1: Output voltage is specified at 1A switch current ISW, which is equivalent to approximately 1A ✕(VIN/ V

OUT

) of load current.

Note 2: Load regulation is measured by forcing specified switch current and straight-line calculation of change in output voltage in

external feedback mode. Note that the equivalent load current is approximately I

SW

✕

(VIN/ V

OUT

).

Note 3: Until undervoltage lockout is reached, the device remains in startup mode. Do not apply full load until this voltage is

reached.

Note 4: Startup is tested with Figure 1’s circuit. Output current is measured when both the input and output voltages are applied.
Note 5: Minimum operating voltage. The MAX1709 is bootstrapped and will operate down to a 0.7V input once started.
Note 6: Supply current is measured from the OUT pin to the output voltage (+3.3V). This correlates directly with actual input supply

current but is reduced in value according to the step-up ratio and efficiency.

Note 7: ONA and ONB inputs have approximately 0.15V hysteresis.
Note 8: Guaranteed by design, not production tested.
Note 9: Specifications to -40°C are guaranteed by design, not production tested.

MAX1709

4A, Low-Noise, High-Frequency,
Step-Up DC-DC Converter

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(V

OUT

= V

CLK

= +3.6V, ONA = ONB = FB = GND, TA= -40°C to +85°C, unless otherwise noted.) (Note 9)

PARAMETER CONDITIONS MIN

TYP

MAX

UNITS

ONA, ONB, 3.3/5, 1.2V < V

OUT

< 5.5V

0.2 ×

V

Input Low Level (Note 7)

CLK, 2.7V < V

OUT

< 5.5V

0.2 ×

ONA, ONB, 3.3/5, 1.2V < V

OUT

< 5.5V

0.8 ×

Input High Level

CLK, V

OUT

= 5.5V

0.8 ×

V

Logic Input Current ONA, ONB, CLK, 3.3/5 1 µA

Internal Oscillator Frequency 500 700

kHz

Maximum Duty Cycle 80 95 %

External Clock Frequency
Range

350

kHz

CLK/SEL Pulse Width (Note 8) 100 ns

CLK/SEL Rise/Fall Time (Note 8) 50 ns

V

V

OUT

OUT

V

V

OUT

OUT

1000

MAX1709

4A, Low-Noise, High-Frequency,

Step-Up DC-DC Converter

_______________________________________________________________________________________ 5

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

100

0

0.001 0.1 10.01 10

EFFICIENCY vs.

OUTPUT CURRENT (V

OUT

= 3.3V)

MAX1709 TOC01

OUTPUT CURRENT (A)

EFFICIENCY (%)

10

20

30

40

50

60

70

80

90

V

IN

= 2.5V

V

IN

= 1.2V

100

0

0.001 0.1 10.01 10

EFFICIENCY vs.

OUTPUT CURRENT (V

OUT

= 5V)

MAX1709 TOC02

OUTPUT CURRENT (A)

EFFICIENCY (%)

10

20

30

40

50

60

70

80

90

V

IN

= 3.3V

V

IN

= 2.5V

83.0

84.0

83.5

85.0

84.5

86.0

85.5

0.4 0.6 0.70.5 0.8 0.9 1.0

EFFICIENCY vs. SWITCHING FREQUENCY

(V

IN

= 3.3V, V

OUT

= 5V, I

OUT

= 2A)

MAX1709 TOC03

OPERATING FREQUENCY (MHz)

EFFICIENCY (%)

2

1

0

-1

-2
021 345

LOAD REGULATION

(V

IN

= 3.3V, V

OUT

= 5V)

MAX1709 TOC04

OUTPUT CURRENT (A)

V

OUT

REGULATION (%)

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

2.0 2.5 3.0 3.5 4.0

LINE REGULATION

(V

OUT

= 5V, I

OUT

= 1A)

MAX1709 TOC05

INPUT VOLTAGE (V)

V

OUT

REGULATION (%)

1000

0.1
0 1.00.5 2.0 3.5

NO-LOAD INPUT CURRENT

vs. INPUT VOLTAGE

1

10

100

MAX1709 TOC06

INPUT VOLTAGE (V)

INPUT CURRENT (mA)

1.5 2.5 3.0

V

OUT

= 3.3V

V

OUT

= 5V

INPUT VOLTAGE

INCREASING

INPUT VOLTAGE

DECREASING

2.8

0.6

0.001 0.1 10.01 10

STARTUP VOLTAGE
vs. LOAD CURRENT

MAX1709 TOC07

LOAD CURRENT (A)

STARTUP VOLTAGE (V)

1.0

0.8

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

TA = -40°C

TA = +25°C

TA = +85°C

V

OUT

= 3.3V

V

OUT

= 5V

-2.0

-1.0

-1.5

0

-0.5

0.5

1.0

-40 10 35-15 60 85

SWITCHING FREQUENCY

vs. TEMPERATURE

MAX1709 TOC08

TEMPERATURE (°C)

FREQUENCY CHANGE (%)

V

OUT

= 3.3V

-5

0.1 1 10

NOISE vs. FREQUENCY

5

0

MAX1709 TOC09

FREQUENCY (MHz)

NOISE (mV

RMS

)

15

10

20

25

30

-10