Rainbow Electronics MAX849 User Manual

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General Description

The MAX848/MAX849 boost converters set a new stan­dard of high efficiency and high integration for noise­sensitive power-supply applications, such as portable
phones and small systems with RF data links. The heart
of the these devices is a synchronous boost-topology
regulator that generates a fixed 3.3V output (or 2.7V to

5.5V adjustable output) from one to three NiCd/NiMH
cells or one Li-Ion cell.

Synchronous rectification provides a 5% efficiency
improvement over similar nonsynchronous boost regu­lators. In standby mode, pulse-skipping PFM operation
keeps the output voltage alive with only 150µW quies­cent power consumption. Fixed-frequency PWM opera­tion ensures that the switching noise spectrum is limited
to the 300kHz fundamental and its harmonics, allowing
easy post-filtering noise reduction. For even tighter
noise spectrum control, synchronize to a 200kHz to
400kHz external clock.

Battery monitoring is provided by a two-channel, volt­age-to-frequency analog-to-digital converter (ADC).
One channel is intended for a single-cell battery input
(0.625V to 1.875V range), while the other channel is for
monitoring higher voltages (0V to 2.5V range).

Two control inputs are provided for push-on, push-off
control via a momentary pushbutton switch. Upon
power-up, an internal comparator monitors the output
voltage to generate a power-good output (POK).

The devices differ only in the current limit of the
N-channel MOSFET power switch: 0.8A for the
MAX848, and 1.4A for the MAX849.

Features

♦ Up to 95% Efficiency

(see

Typical Output Selector Guide

below)

♦ 3.3V Dual Mode™ or 2.7V to 5.5V Adj. Output
♦ 0.7V to 5.5V Input Range
♦ 0.15mW Standby Mode
♦ 300kHz PWM Mode or Synchronizable
♦ Two-Channel ADC with Serial Output
♦ Power-Good Function

Applications

Digital Cordless Phones PCS Phones
Cellular Phones Hand-Held Instruments
Palmtop Computers Personal Communicators
Local 3.3V to 5V Supplies

MAX848/MAX849

1-Cell to 3-Cell, High-Power,

Low-Noise, Step-Up DC-DC Converters

________________________________________________________________

Maxim Integrated Products

1

AIN1
AIN2
AINSEL
DATA
ON1
ON2
CLK/SEL
POKIN

LX

OUT

POUT

POK

FB

MAX848
MAX849

OUTPUT

A/D CHANNEL 1 IN
A/D CHANNEL 2 IN

A/D CHANNEL SELECT

A/D OUTPUT

ON/OFF CONTROL

SYNC INPUT

INPUT

0.8V TO 5.5V

VOLTAGE MONITOR
OUTPUT

REF

GND PGND

Typical Operating Circuit

19-1095; Rev 2; 12/97

PART

MAX848ESE
MAX849ESE

-40°C to +85°C

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

16 Narrow SO
16 Narrow SO

Ordering Information

Pin Configuration appears at end of data sheet.

Dual Mode is a trademark of Maxim Integrated Products.

Typical Output Selector Guide

V

IN

(V)

V

OU

T

(V)

MAX849 I

OUT

(mA)

MAX848 I

OUT

(mA)

0.9

3.3 100 70
5 70 40

1.2

3.3 300 110
5 200 70

2.4

3.3 750 200
5 500 130

2.7

3.3 800 250
5 600 150

3.6 5 1000 300

mA

MAX848/MAX849

1-Cell to 3-Cell, High-Power,
Low-Noise, Step-Up DC-DC Converters

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

OUT

= 3.6V, GND = PGND = CLK/SEL = ON1 = ON2 = AINSEL = AIN1 = AIN2 = FB = POKIN, POUT = OUT, TA= 0°C to +85°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.

ON1, ON2, OUT, POUT to GND..................................-0.3V, +6V

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

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

POUT

+ 0.3V)

CLK/SEL, DATA, POKIN, REF,

AINSEL, AIN1, AIN2, FB, POK to GND .....-0.3V, (V

OUT

+ 0.3V)

Continuous Power Dissipation (T

A

= +70°C)

Narrow SO (derate 8.7mW/°C above +70°C) ................696mW

Operating Temperature Range

MAX848ESE/MAX849ESE .................................-40°C to +85°C

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

Storage Temperature.........................................-65°C to +160°C

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

110
300

70

VIN= 1.2V

200
200
750

V

OUT

= 5V

mA

1000

130

Output Current

VIN= 2.4V

500

I

REF

= 0mA

250
600
150

VIN= 2.7V

800

µA4 20

300

Operating Current in Shutdown

kHz40 300Frequency in Start-Up Mode

V0.9 1.1Minimum Start-Up Voltage (Note 5)

%-1.6

(Note 3)

Load Regulation (Note 4)

V1.23 1.25 1.27Reference Output Voltage

Current into OUT pin, V

ON2

= 3.6V

V0.7

V

OUT

= 1.5V

Minimum Operating Voltage (Note 1)

V2.1 2.4

VFB= 1.25V

Output Voltage Lockout Range

V2.7 5.5

Adjustable output, CLK/SEL = OUT

Output Voltage Adjust Range

nA200

-1µA < I

REF

< 50µA

FB Input Current

V1.215 1.240 1.265

2.5V < V

OUT

< 5V

FB Regulation Voltage

mV5 15REF Load Regulation
mV0.2 5

I

LOAD

< 1mA, TA> +25°C

REF Supply Rejection

VFB< 0.1V, CLK/SEL = OUT V3.17 3.34 3.40

CLK/SEL = OUT

Output Voltage (Note 2)

UNITSMIN TYP MAXPARAMETER

MAX848
MAX849
MAX848
MAX849
MAX848
MAX849
MAX848
MAX849
MAX848
MAX849
MAX848
MAX849

CONDITIONS

V

OUT

= 3.3V

V

OUT

= 5V

V

OUT

= 3.3V

MAX849, VIN= 3.6V

V

OUT

= 5V

V

OUT

= 3.3V

V

OUT

= 5V

MAX848, VIN= 3.3V

DC-DC CONVERTER

REFERENCE

MAX848/MAX849

1-Cell to 3-Cell, High-Power,

Low-Noise, Step-Up DC-DC Converters

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

OUT

= 3.6V, GND = PGND = CLK/SEL = ON1 = ON2 = AINSEL = AIN1 = AIN2 = FB = POKIN, POUT = OUT, TA= 0°C to +85°C,

unless otherwise noted.)

Input Low Voltage

1.2V < V

OUT

< 5.5V, ON1 and ON2 (Note 8)

0.2V

OUT

Accuracy

V

Current into OUT pin, CLK/SEL = GND

V

OUT

= 2.7V, AINSEL and CLK/SEL

f

CLK

= 400kHz, 5ms conversion,

monotonic to 8 bits

±4 % FSR

0.2V

OUT

Internal Trip Level

µA

Rising V

OUT

, V

POKIN

< 0.1V 2.95 3.10 V

External Trip Level

Input High Voltage

Rising V

POKIN

1.225 1.275

µA1 2f

CLK

= 400kHz, V

AIN1

= V

AIN2

= 2.5VAIN1, AIN2 Input Current

V0 2.5AINSEL = OUTAIN2 Input Voltage Range

V0.625 1.875AINSEL = GNDAIN1 Input Voltage Range

VV

OUT

- 0.4

V

Data Output Voltage High

V0.4

I

SOURCE

= 1mA

Data Output Voltage Low I

SINK

= 1mA

POK Low Voltage

1.2V < V

OUT

< 5.5V, ON1 and ON2 (Note 8)

I

SINK

= 1mA, V

OUT

= 3.6V or

I

SINK

= 20µA, V

OUT

= 1V

0.4 V

POK High Leakage Current

0.8V

OUT

V

OUT

= V

POK

= 5.5V 0.01 1 µA

POKIN Leakage Current

V

V

POKIN

= 1.5V 50 nA

35 90

V

OUT

= 5.5V, AINSEL and CLK/SEL 0.8V

OUT

Operating Current in Low-Power
Mode (Note 6)

Logic Input Current

ON1, ON2, AINSEL and CLK/SEL

1 µA
Internal Oscillator Frequency CLK/SEL = OUT 260 300 340 kHz
Oscillator Maximum Duty Cycle 80 85 90 %
External Clock Frequency Range 200 400 kHz
CLK/SEL Pulse Width Not tested 200 ns
CLK/SEL Rise/Fall Time Not tested 100 ns

Current into OUT pin, CLK/SEL = OUT,
does not include switching losses

µA

150 300

UNITS

MIN TYP MAX

CONDITIONSPARAMETER

Operating Current in Low-Noise
Mode (Note 6)

VLX= 0V, V

ON2

= V

OUT

= 5.5V µA0.1 20POUT Leakage Current

VLX= V

ON2

= V

OUT

= 5.5V µA0.1 20LX Leakage Current

N-channel

0.3 0.6

CLK/SEL = GND

0.13 0.25

CLK/SEL = OUT

P-channel

Ω

0.25 0.5

Switch On-Resistance

CLK/SEL = OUT

600 800 1000MAX848

CLK/SEL = OUT

1100 1350 1600MAX849

120 200 300MAX848

V

CLK/SEL

= 0V (Note 7)

mA

250 400 550

N-Channel Current Limit

MAX849

DC-DC SWITCHES

ADC

POWER-GOOD

LOGIC AND CONTROL INPUTS

MAX848/MAX849

1-Cell to 3-Cell, High-Power,
Low-Noise, Step-Up DC-DC Converters

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

(V

OUT

= 3.6V, GND = PGND = CLK/SEL = ON1 = ON2 = AINSEL = AIN1 = AIN2 = FB = POKIN, POUT = OUT, TA= -40°C to +85°C,

unless otherwise noted.) (Note 9)

Note 1: Minimum operating voltage. Because the MAX848/MAX849 are bootstrapped to the output, it will operate down to a 0.7V input.
Note 2: In low-power mode (CLK/SEL = GND), the output voltage regulates 1% higher than in low-noise mode (CLK/SEL = OUT or

synchronized).

Note 3: The part is in start-up mode until it reaches this voltage level. Do not apply full-load current.
Note 4: Load regulation is measured from no load to full load, where full load is determined by the N-channel switch current limit.
Note 5: Start-up is tested with Figure 2’s circuit. Output current is measured when the input and output voltages are applied.
Note 6: Supply current from the 3.34V output is measured between the 3.34V output and the OUT pin. This current correlates directly

with actual battery supply current, but is reduced in value according to the step-up ratio and efficiency. V

OUT

= 3.6V to keep

the internal switch open when measuring the current into the device.

Note 7: When V

CLK/SEL

= 0V, the inductor is forced into constant-peak-current, discontinuous operation. This is guaranteed by

testing in Figure 2’s circuit.

Note 8: ON1 and ON2 inputs have approximately 0.15V

OUT

hysteresis.

Note 9: Specifications to -40°C are guaranteed by design, not production tested.

%80 90Oscillator Maximum Duty Cycle

kHz260 340CLK/SEL = OUTInternal Oscillator Frequency

V1.225 1.275Rising V

POKIN

External Trip Level

V2.95 3.10Rising V

OUT

, V

POKIN

< 0.1VInternal Trip Level

% FSR±4f

CLK

= 400kHz, 5ms conversionAccuracy

250 550MAX849

CLK/SEL = GND (Note 7)

N-Channel Current Limit

120 300MAX848

PARAMETER CONDITIONS

MIN TYP MAX

UNITS

1100 1800MAX849

CLK/SEL = OUT

mA

600 1100MAX848

0.5CLK/SEL = OUTP-channel

Switch On-Resistance 0.25CLK/SEL = OUT

N-channel

I

REF

= 0mAReference Output Voltage 1.225 1.275 V

Ω

Output Voltage (Note 3)

VFB< 0.1V, CLK/SEL = OUT,
includes load-regulation error

3.13 3.47 V

FB Regulation Voltage Adjustable output, CLK/SEL = OUT 1.21 1.27 V
Output Voltage Lockout Range (Note 3) 2.05 2.45 V

0.6CLK/SEL = GND

µA300

CLK/SEL = OUT, does not include
switching losses

OUT Supply Current in Low-Noise
Mode (Note 6)

µA90CLK/SEL = GND

OUT Supply Current in Low-Power
Mode (Note 6)

OUT Supply Current in Shutdown V

ON2

= 3.6V 20 µA

REFERENCE

DC-DC CONVERTER

DC-DC SWITCHES

ADC

POWER-GOOD

LOGIC CONTROL INPUTS

MAX848/MAX849

1-Cell to 3-Cell, High-Power,

Low-Noise, Step-Up DC-DC Converters

_______________________________________________________________________________________

5

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

100

90

40

0.1 1 10 100 1000

MAX849

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 3.3V)

50

MAX848/9 TOC-01

LOAD CURRENT (mA)

EFFICIENCY (%)

60

70

80

VIN = 2.4V

PFM
PWM

VIN = 0.9V

VIN = 1.2V

100

90

40
30

0.1 1 10 100 1000

MAX849

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 5V)

50

MAX848/9 TOC-02

LOAD CURRENT (mA)

EFFICIENCY (%)

60

70

80

VIN = 1.2V

VIN = 2.4V

VIN = 3.6V

PFM
PWM

70

60

0.1 1 10 100 1000

MAX848

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 3.3V)

80

MAX848/9 TOC-03

LOAD CURRENT (mA)

EFFICIENCY (%)

90

100

VIN = 2.4V

VIN = 1.2V

VIN = 0.9V

PFM
PWM

14

0

0 2 31 4 6

NO-LOAD BATTERY CURRENT

vs. INPUT VOLTAGE

4

12

MAX848/9 TOC-04

INPUT VOLTAGE (V)

INPUT CURRENT (mA)

5

8

2

10

6

TA = +85°C

TA = +25°C

TA = -40°C

1.252

1.248

-40 0

-20

20 60 10080

REFERENCE VOLTAGE

vs. TEMPERATURE

1.249

1.251

MAX848/9 TOC-07

TEMPERATURE (°C)

REFERENCE VOLTAGE (V)

40

1.250

18

14

0

0 21 3 65

SHUTDOWN CURRENT

vs. INPUT VOLTAGE

4

16

12

MAX848/9 TOC-05

SHUTDOWN CURRENT (µA)

4

8

2

10

6

TA = +85°C

TA = +25°C

TA = -40°C

INCLUDES ALL EXTERNAL
COMPONENT LEAKAGES.
CAPACITOR LEAKAGE
DOMINATES AT
T

A

= +85°C

INPUT VOLTAGE (V)

2.0

1.8

1.6

0.6

0.01 0.1 1 10 100 1000

START-UP VOLTAGE vs. LOAD CURRENT

(V

OUT

= 3.3V, PWM MODE)

0.8

MAX848/9 TOC-06

LOAD CURRENT (mA)

START-UP VOLTAGE (V)

1.0

1.2

1.4

TA = +85°C

TA = +25°C

TA = -40°C

1.252

1.238
0 2010 30 50 60 70 80

REFERENCE VOLTAGE

vs. REFERENCE CURRENT

1.242

1.250

MAX848/9 TOC-08

REFERENCE CURRENT (µA)

REFERENCE VOLTAGE (V)

40

1.246

1.240

1.248

1.244

0.25

-0.25

0.1875 0.68750.4375 0.9375

ADC LINEARITY ERROR

vs. FULL-SCALE INPUT VOLTAGE

0.15

MAX848/9 TOC-09

FULL-SCALE INPUT VOLTAGE (V)

LINEARITY ERROR (%FS)

-0.15

0.05

-0.05
AIN1

AIN2