Maxim MAX1790EUA Datasheet

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General Description

The MAX1790 boost converter incorporates high-perfor­mance (at 1.2MHz), current-mode, fixed-frequency, pulse­width modulation (PWM) circuitry with a built-in 0.21Ω
N-channel MOSFET to provide a highly efficient regulator
with fast response.

High switching frequency (640kHz or 1.2MHz selectable)
allows easy filtering and faster loop performance. An
external compensation pin provides the user flexibility in
determining loop dynamics, allowing the use of small, low
equivalent series resistance (ESR) ceramic output capaci­tors. The device can produce an output voltage as high as
12V from an input as low as 2.6V.

Soft-start is programmed with an external capacitor, which
sets the input current ramp rate. In shutdown mode, cur­rent consumption is reduced to 0.1µA. The MAX1790 is
available in a space-saving 8-pin µMAX package. The
ultra-small package and high switching frequency allow
the total solution to be less than 1.1mm high.

Applications

LCD Displays

PCMCIA Cards

Portable Applications

Hand-Held Devices

Features

♦ 90% Efficiency

♦ Adjustable Output from V

IN

to 12V

♦ 1.6A, 0.21Ω, 14V Power MOSFET

♦ +2.6V to +5.5V Input Range

♦ Pin-Selectable 640kHz or 1.2MHz Switching

Frequency

♦ 0.1µA Shutdown Current

♦ Programmable Soft-Start

♦ Small 8-Pin µMAX Package

MAX1790

Low-Noise Step-Up DC-DC Converter

________________________________________________________________ Maxim Integrated Products 1

Typical Operating Circuit

19-1563; Rev 0; 1/00

PART

MAX1790EUA -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

8 µMAX

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

Pin Configuration

Ordering Information

V

IN

2.6V TO 5V

ON/OFF

TOP VIEW

1

IN

SHDN

FREQ

SS

LX

MAX1790

GND

FB

COMP

V

OUT

COMP

SHDN

2

3

4

87SS

MAX1790

µMAX

FREQFB

IN

6

LXGND

5

MAX1790

Low-Noise Step-Up DC-DC Converter

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= SHDN = 3V, FREQ = 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.

LX to GND ..............................................................-0.3V to +14V

IN, SHDN, FREQ, FB to GND ...................................-0.3V to +6V

SS, COMP to GND.......................................-0.3V to (V

IN

+ 0.3V)

RMS LX Pin Current ..............................................................1.2A

Continuous Power Dissipation (T

A

= +70°C)

8-Pin µMAX (derate 4.1mW/°C above +70°C) ...........330mW

Operating Temperature Range

MAX1790EUA ................................................-40°C to +85°C

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

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

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

VSS= 1.2V

VFB= 1.3V, not switching

VLX= 12V

VINrising, typical hysteresis is 40mV,
LX remains off below this level

ILX= 1.2A

VFB= 1V, duty cycle = 65%

FREQ = IN

∆I = 5µA

FREQ = GND

FREQ = IN

Level to produce V

COMP

= 1.24V,

2.6V < V

IN

< 5.5V

VFB= 1.24V

VFB= 1.0V, switching
SHDN = GND

FREQ = GND

Level to produce V

COMP

= 1.24V

CONDITIONS

µA

1.5 4 7

Charge Current

Ω

100

Reset Switch Resistance

V/A

0.3 0.45 0.65

R

CS

Current-Sense Transresistance

µA

0.01 20

I

LXOFF

Leakage Current

Ω

0.21 0.5

R

ON

On-Resistance

A

1.2 1.6 2.3

I

LIM

Current Limit (Note 1)

84

%

79 85 92

DCMaximum Duty Cycle

1000 1220 1500

kHz

540 640 740

f

OSC

Frequency

mA

0.18 0.35

I

IN

Quiescent Current

V

2.25 2.38 2.52

UVLO

V

2.6 5.5

V

IN

Input Supply Range

VINUndervoltage Lockout

V/V

700

A

V

Voltage Gain

µmhos

70 140 240

g

m

Transconductance

%/V

0.05 0.15

Feedback-Voltage Line
Regulation

nA

040

I

FB

FB Input Bias Current

25

µA

0.1 10

I

IN

Shutdown Supply Current

V

1.222 1.24 1.258

V

FB

Feedback Voltage

UNITSMIN TYP MAXSYMBOLPARAMETER

SHDN, FREQ

SHDN, FREQ; VIN= 2.6V to 5.5V

SHDN, FREQ; VIN= 2.6V to 5.5V

µA

0.001 1

I

SHDN

SHDN Input Current

µA

1.8 5 9

I

FREQ

FREQ Pull-Down Current

V

0.1 · V

IN

Hysteresis

V

0.7 · V

IN

V

IH

Input High Voltage

V

0.3 · V

IN

V

IL

Input Low Voltage

ERROR AMPLIFIER

OSCILLATOR

N-CHANNEL SWITCH

SOFT-START

CONTROL INPUTS

MAX1790

Low-Noise Step-Up DC-DC Converter

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS

(VIN= SHDN = 3V, FREQ = GND, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)

Note 1: Current limit varies with duty cycle due to slope compensation. See the Output Current Capability section.
Note 2: Specifications to -40°C are guaranteed by design and not production tested.

PARAMETER SYMBOL MIN TYP MAX UNITS

Feedback Voltage V

FB

1.215 1.26

V

Shutdown Supply Current I

IN

10

µA

45

FB Input Bias Current I

FB

40

nA

Feedback-Voltage Line
Regulation

0.15

%/V

Transconductance g

m

70 260

µmhos

V

IN

Undervoltage Lockout

Input Supply Range V

IN

2.6 5.5

V

UVLO

2.25 2.52

V

Quiescent Current I

IN

0.2 0.35
mA

Frequency f

OSC

490 770

kHz

900 1500

Maximum Duty Cycle DC

78 92

%

Current Limit I

LIM

1.2 2.3

A

On-Resistance R

ON

0.5

Ω

Current-Sense Transresistance R

CS

0.3 0.65

V/A

Input Low Voltage V

IL

0.3 · V

IN

V

Input High Voltage V

IH

0.7 · V

IN

V

CONDITIONS

FREQ = GND

Level to produce V

COMP

= 1.24V

FREQ = IN

SHDN = GND

VFB= 1.0V, switching

VFB= 1.24V

Level to produce V

COMP

= 1.24V,

2.6V < VIN< 5.5V

FREQ = GND

∆I = 5µA

VFB= 1V, duty cycle = 65%

ILX= 1.2A

V

IN

rising, typical hysteresis is 40mV,

LX remains off below this level

SHDN, FREQ, VIN= 2.6V to 5.5V
SHDN, FREQ, VIN= 2.6V to 5.5V

VFB= 1.3V, not switching

ERROR AMPLIFIER

OSCILLATOR

N-CHANNEL SWITCH

CONTROL INPUTS

MAX1790

Low-Noise Step-Up DC-DC Converter

4 _______________________________________________________________________________________

Typical Operating Characteristics

(Circuit of Figure 1, VIN= 3.3V, f

OSC

= 640kHz, TA= +25°C, unless otherwise noted.)

MAX1790-01

50

1 100010010

EFFICIENCY vs. OUTPUT CURRENT

65

55

85

75

95

70

60

90

80

OUTPUT CURRENT (mA)

EFFICIENCY (%)

f

OSC

= 1.2MHz

L

= 2.7µH

V

IN

= 3.3V

V

OUT

= 5V

f

OSC

= 640kHz

L

= 5.4µH

50

1 100010010

EFFICIENCY vs. OUTPUT CURRENT

65

55

85

75

95

70

60

90

80

MAX1790-02

OUTPUT CURRENT (mA)

EFFICIENCY (%)

f

OSC

= 1.2MHz

L

= 5.4µH

V

IN

= 3.3V

V

OUT

= 12V

f

OSC

= 640kHz

L

= 10µH

OUTPUT CURRENT (mA)

50

1 100010010

EFFICIENCY vs. OUTPUT CURRENT

65

55

85

75

95

70

60

90

80

MAX1790-03

EFFICIENCY (%)

f

OSC

= 1.2MHz

L

= 5.4µH

V

IN

= 5V

V

OUT

= 12V

f

OSC

= 640kHz

L

= 10µH

0

0.2

0.1

0.4

0.3

0.6

0.5

0.7

2.5 3.5 4.03.0 4.5 5.0 5.5

NO-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE

MAX1790-04

INPUT VOLTAGE (V)

NO-LOAD SUPPLY CURRENT (mA)

V

OUT

= 12V

f

OSC

= 1.2MHz

f

OSC

= 640kHz

11.60

11.70

11.65

11.80

11.75

11.90

11.85

11.95

12.05

12.00

12.10

0 40608020 100 120 140 180160 200

OUTPUT VOLTAGE vs. OUTPUT CURRENT

MAX1790-05

OUTPUT CURRENT (mA)

OUTPUT VOLTAGE (V)

f

OSC

= 640kHz

TA = +85°C

TA = +25°C

TA = -40°C

200mA

10mA

CH1

CH2

CH3

CH1 = LOAD CURRENT, 100mA/div
CH2 = OUTPUT VOLTAGE, AC-COUPLED, 200mV/div
CH3 = INDUCTOR CURRENT, 1A/div
V

IN

= 3V

V

OUT

= 12V, f

OSC

= 640kHz, C

OUT

= 33µF + 0.1µF

100µs/div

LOAD-TRANSIENT RESPONSE

MAX1790-06

R

COMP

= 120kΩ

C

COMP

= 1200pF

C

COMP2

= 56pF