Rainbow Electronics MAX1760 User Manual

General Description

The MAX1760 is a high-efficiency, low-noise, step-up
DC-DC converter intended for use in battery-powered
wireless applications. It maintains exceptionally low qui­escent supply current (100µA) despite its high 1MHz
operating frequency. Small external components and a
tiny 10-pin µMAX package make this device an excel­lent choice for small hand-held applications requiring
the longest possible battery life.

The MAX1760 uses a synchronous-rectified pulse­width-modulation (PWM) boost topology to generate

2.5V to 5.5V outputs from a wide range of input
sources, such as 1 to 3 alkaline or NiCd/NiMH cells or a
single lithium-ion (Li+) cell. Maxim's proprietary Idle­Mode™ circuitry significantly improves efficiency at
light load currents while smoothly transitioning to fixed­frequency PWM operation at higher load currents to
maintain excellent full-load efficiency.

Low-noise, forced PWM mode is available for applica­tions requiring constant-frequency operation at all load
currents. The MAX1760 may also be synchronized to
an external clock to protect sensitive frequency bands
in communications equipment. Analog soft-start and
adjustable current limit permit optimization of efficiency,
external component size, and output voltage ripple.

Applications

Digital Cordless Phones PCS Phones

Wireless Handsets Hand-Held Instruments

Palmtop Computers Personal Communicators

Two-Way Pagers

Features

♦ Up to 94% Efficiency

♦ 0.7V to 5.5V Input Range

♦ Up to 800mA Output

♦ Fixed 3.3V Output (or adj from 2.5V to 5.5V)

♦ PWM Synchronous Rectified Topology

♦ Low-Noise, Constant Frequency Operation (1MHz)

♦ 0.1µA Logic-Controlled Shutdown

♦ Synchronizable Switching Frequency

♦ Adjustable Current Limit

♦ Adjustable Soft-Start

♦ 10-Pin µMAX Package

MAX1760

0.8A, Low-Noise, 1MHz,

Step-Up DC-DC Converter

________________________________________________________________ Maxim Integrated Products 1

Typical Operating Circuit

19-1660; Rev 1; 1/01

PART

MAX1760EUB -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

10 µMAX

EVALUATION KIT

AVAILABLE

Idle Mode is a trademark of Maxim Integrated Products.

Pin Configuration

Ordering Information

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

INPUT = 0.7V

TO V

OUT

MAX1760

ON

CLK/SEL

ISET

REF

FB GND

LX

POUT

OUT

PGND

V

OUT

800mA

= 3.3V,

TOP VIEW

ISET

REF

GND

1

2

MAX1760

3

4

5

µMAX

ON

10

9

POUT

8

LX

7

PGNDFB

CLK/SELOUT

6

MAX1760

0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(CLK/SEL = ON = FB = PGND = GND, ISET = REF, OUT = POUT, V

OUT

= 3.6V, TA= 0°C to +85°C. Typical values are at TA=

+25°C, unless otherwise noted.)

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.

ON, OUT, CLK/SEL to GND .....................................-0.3V to +6V

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

LX to PGND ............................................-0.3V to (V

POUT

+ 0.3V)

POUT to OUT ......................................................................±0.3V

REF, FB, ISET, POUT to GND...................-0.3V to (V

OUT

+ 0.3V)

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, 10s) .................................+300°C

DC-DC CONVERTER

Input Voltage Range (Note 1) 0.7 5.5 V

Minimum Startup Voltage (Note 2) I

Temperature Coefficient of Startup Voltage I

Frequency in Startup Mode V

Internal Oscillator Frequency CLK/SEL = OUT 0.8 1 1.2 MHz

Oscillator Maximum Duty Cycle (Note 3) 80 86 90 %

External Clock Frequency Range 0.5 1.2 MHz

Output Voltage

FB Regulation Voltage

FB Input Leakage Current VFB = 1.35V 0.01 100 nA

Load Regulation

Output Voltage Adjust Range 2.5 5.5 V

Output Voltage Lockout Threshold (Note 4) Rising edge 2.00 2.15 2.30 V

ISET Input Leakage Current V

Supply Current in Shutdown V ON = 3.6V 0.1 5 µA
No-Load Supply Current (Note 5) CLK/SEL = GND 100 185 µA

No-Load Supply Current Forced PWM Mode CLK/SEL = OUT 2.5 mA

DC-DC SWITCHES

POUT Leakage Current VLX = 0, V

LX Leakage Current V

Switch On-Resistance

N-Channel Current Limit 1.0 1.25 1.6 A

P-Channel Turn-Off Current CLK/SEL = GND 20 60 120 mA

PARAMETER CONDITIONS MIN TYP MAX UNITS

< 1mA, TA = +25°C 0.9 1.1 V

LOAD

< 1mA -2.3 mV/°C

LOAD

= 1.5V 125 500 1000 kHz

OUT

V

< 0.1V, CLK/SEL = OUT, includes load

FB

regulation for 0 < I

Adjustable output, CLK/SEL = OUT, includes
load regulation for 0 < I

CLK/SEL = OUT, no load to full load

< 1.0A)

(0 < I

LX

= 1.25V ±0.01 ±50 nA

ISET

OUT

= V

LX

ON

N-channel 0.15 0.28

P-channel 0.25 0.45

LX

= 5.5V 0.1 10 µA

= 5.5V 0.1 10 µA

= V

OUT

< 0.55A

< 0.55A

LX

3.17 3.3 3.38 V

1.215 1.240 1.270 V

-1.5 %

Ω

MAX1760

0.8A, Low-Noise, 1MHz,

Step-Up DC-DC Converter

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS

(CLK/SEL = ON = FB = PGND = GND, ISET = REF, OUT = POUT, V

OUT

= 3.6V, TA= -40°C to +85°C, unless otherwise noted.) (Note 7)

ELECTRICAL CHARACTERISTICS (continued)

(CLK/SEL = ON = FB = PGND = GND, ISET = REF, OUT = POUT, V

OUT

= 3.6V, TA= 0°C to +85°C. Typical values are at TA= +25°C

unless otherwise noted.)

REFERENCES

Reference Output Voltage I

Reference Load Regulation -1µA < IREF < 50µA 5 15 mV

Reference Supply Rejection 2.5V < V

LOGIC INPUTS

CLK/SEL Input Low Level 2.5V ≤ V

CLK/SEL Input High Level 2.5V ≤ V

ON Input Low Level (Note 6)

ON Input High Level (Note 6)

Input Leakage Current CLK/SEL, ON 0.01 1 µA

Minimum CLK/SEL Pulse Width 200 ns

Maximum CLK/SEL Rise/Fall Time 100 ns

PARAMETER CONDITIONS MIN TYP MAX UNITS

= 0 1.230 1.250 1.270 V

REF

< 5V 0.2 5 mV

OUT

≤ 5.5V (0.2)V

OUT

≤ 5.5V (0.8)V

OUT

1.1V ≤ V

1.8V ≤ V

1.1V ≤ V

1.8V ≤ V

≤ 1.8V 0.2

OUT

≤ 5.5V 0.4

OUT

≤ 1.8V V

OUT

≤ 5.5V 1.6

OUT

OUT

OUT

- 0.2

OUT

V

V

V

V

DC-DC CONVERTER

Output Voltage

FB Regulation Voltage

Internal Oscillator Frequency CLK/SEL = OUT 0.75 1.2 MHz

Oscillator Maximum Duty Cycle (Note 3) 80 90 %

Output Voltage Lockout Threshold (Note 4) Rising edge 2.00 2.30 V

Supply Current in Shutdown V ON = 3.6V 5 µA
No-Load Supply Current (Note 5) CLK/SEL = GND 185 µA

DC-DC SWITCHES

Switch On-Resistance

N-Channel Current Limit 1.0 1.6 A

REFERENCE

Reference Output Voltage I

PARAMETER CONDITIONS MIN MAX UNITS

V

< 0.1V, CLK/SEL = OUT, includes load

FB

regulation for 0 < I

Adjustable output, CLK/SEL = OUT, includes
load regulation for 0 < I

N-channel 0.28

P-channel 0.45

= 0 1.230 1.270 V

REF

< 0.55A

LX

< 0.55A

LX

3.17 3.38 V

1.215 1.270 V

Ω

MAX1760

0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter

4 _______________________________________________________________________________________

Note 1: Operating voltage—since the regulator is bootstrapped to the output, once started the MAX1760 will operate down

to 0.7V input.

Note 2: Startup is tested with the circuit shown in Figure 6.
Note 3: Defines maximum step-up ratio.
Note 4: The regulator is in startup mode until this voltage is reached. Do not apply full load current until the output exceeds 2.3V.
Note 5: Supply current into the OUT pin. This current correlates directly to the actual battery-supply current, but is reduced in

value according to the step-up ratio and efficiency.

Note 6: ON has a hysteresis of approximately 0.15

× V

OUT

.

Note 7: Specifications to -40°C are guaranteed by design and not production tested.

100

0

0.0001 0.001 0.01 0.1 1

EFFICIENCY vs. OUTPUT CURRENT

V

OUT

= 3.3V

20

MAX1760 toc01

OUTPUT CURRENT (A)

EFFICIENCY (%)

40

70

90

60

80

10

30

50

A

B

C

A: VIN = 2.4V
B: V

IN

= 1.2V

C: V

IN

= 0.9V

= AUTO MODE

= FPWM MODE

MAX1760-02

100

0

0.0001 0.001 0.01 0.1 1

EFFICIENCY vs. OUTPUT CURRENT

V

OUT

= 5V

20

OUTPUT CURRENT (A)

EFFICIENCY (%)

40

70

90

60

80

10

30

50

A: VIN = 3.6V
B: V

IN

= 2.4V

C: V

IN

= 1.2V

= AUTO MODE

= FPWM MODE

A

B

C

MAXIMUM OUTPUT CURRENT

vs. INPUT VOLTAGE

MAX1760-03

0.1

1.00.5 1.5 2.0 2.5 3.0 3.5 4.0

0.3

0.2

0.5

0.4

0.8

0.7

0.6

0.9

INPUT VOLTAGE (V)

OUTPUT CURRENT (A)

V

OUT

= 3.3V

V

OUT

= 5V

ELECTRICAL CHARACTERISTICS (continued)

(CLK/SEL = ON = FB = PGND = GND, ISET = REF, OUT = POUT, V

OUT

= 3.6V, TA= -40°C to +85°C, unless otherwise noted.) (Note 7)

Typical Operating Characteristics

(Circuit of Figure 2, VIN= 2.4V, V

OUT

= 3.3V, TA= +25°C, unless otherwise noted.)

LOGIC INPUTS

CLK/SEL Input Low Level 2.5V ≤ V
CLK/SEL Input High Level 2.5V ≤ V

ON Input Low Level (Note 6)

ON Input High Level (Note 6)

Input Leakage Current CLK/SEL, ON 1 µA

PARAMETER CONDITIONS MIN MAX UNITS

≤ 5.5V (0.2)V

OUT

≤ 5.5V (0.8)V

OUT

1.1V ≤ V

1.8V ≤ V

1.1V ≤ V

1.8V ≤ V

≤ 1.8V 0.2

OUT

≤ 5.5V 0.4

OUT

≤ 1.8V V

OUT

≤ 5.5V 1.6

OUT

OUT

+ 0.2

OUT

OUT

V

V

V

V