Maxim MAX1678EUA Datasheet

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General Description

The MAX1678 is a high-efficiency, low-voltage, syn­chronous-rectified, step-up DC-DC converter intended
for use in devices powered by 1 to 3-cell alkaline,
NiMH, or NiCd batteries or a 1-cell lithium battery. It
guarantees a 0.87V start-up voltage and features a low
37µA quiescent supply current.

The device includes a 1Ω, N-channel MOSFET power
switch, a synchronous rectifier that acts as the catch
diode, a reference, pulse-frequency-modulation (PFM)
control circuitry, and circuitry to reduce inductor ring­ing—all in an ultra-small, 1.1mm-high µMAX package.

The output voltage is preset to 3.3V or can be adjusted
from +2V to +5.5V using only two resistors. Efficiencies
up to 90% are achieved for loads up to 50mA. The
device also features an independent undervoltage
comparator (PFI/PFO) and a logic-controlled 2µA shut­down mode.

Applications

Pagers
Remote Controls
Pointing Devices
Personal Medical Monitors
Single-Cell Battery-Powered Devices

Features

♦ 0.87V Guaranteed Start-Up
♦ Up to 90% Efficiency
♦ Built-In Synchronous Rectifier (no external diode)
♦ Ultra-Small µMAX Package, 1.1mm High
♦ 37µA Quiescent Current (85µA from 1.5V battery)
♦ 2µA Logic-Controlled Shutdown
♦ Power-Fail Detector
♦ Dual Mode™ Output: Fixed 3.3V

Adjustable 2V to 5.5V

♦ 45mA Output Current at 3.3V for 1-Cell Input
♦ 90mA Output Current at 3.3V for 2-Cell Input
♦ Inductor-Damping Switch Suppresses EMI

MAX1678

1-Cell to 2-Cell, Low-Noise,

High-Efficiency, Step-Up DC-DC Converter

________________________________________________________________

Maxim Integrated Products

1

1
2
3
4

8
7
6
5

OUT
LX
GND
FBSHDN

PFO

PFI

BATT

MAX1678

µMAX

TOP VIEW

Typical Operating Circuit

19-1381; Rev 0; 7/98

PART

MAX1678EUA -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

8 µMAX

EVALUATION KIT

AVAILABLE

Note: To order these devices shipped in tape-and-reel, add a -T
to the part number.

Pin Configuration

Ordering Information

Dual Mode is a trademark of Maxim Integrated Products.

INPUT

0.87V TO V

OUT

ON

OFF

LOW-BATTERY

DETECTOR INPUT

LX

BATT
SHDN

PFI

GND FB

OUT

MAX1678

PFO

OUTPUT

3.3V

LOW-BATTERY
DETECTOR OUTPUT

MAX1678

1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

BATT

= V

SHDN

= 1.3V, I

LOAD

= 0, 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.

Note 1: The reverse battery current is measured from the

Typical Operating Circuit’s

input terminal to GND when the battery is con­nected backward. A reverse current of 220mA will not exceed package dissipation limits but, if left for an extended time
(more than 10 minutes), may degrade performance.

BATT, OUT,LX, SHDN to GND..............................-0.3V to +6.0V

OUT, LX Current.......................................................................1A

FB, PFI, PFO to GND................................-0.3V to (V

OUT

+ 0.3V)

Reverse Battery Current (T

A

= +25°C) (Note 1) ...............220mA

Continuous Power Dissipation (T

A

= +70°C)

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

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

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

Storage Temperature Range.............................-65°C to +165°C

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

V

PFI

= 650mV, V

PFO

= 6V

RL= 3kΩ, TA= +25°C

V

PFI

= 0, V

OUT

= 3.3V, I

SINK

= 1mA

V

PFI

= 650mV

Falling PFI hysteresis 2%

VFB= 1.3V

I

LOAD

= 20mA, V

BATT

= 2.5V (Figure 7)

V

BATT

= 1V

I

DIODE

= 100mA, P-channel switch off

V

OUT

= 3.5V

V

OUT

= 3.3V

V

OUT

= 3.3V

VFB< 0.1V
External feedback

V

OUT

= 3.5V

External feedback

0.9V < V

BATT

< 3.3V (tON= K / V

BATT

)

CONDITIONS

V0.8 x V

BATT

V

IH

SHDN Input High Voltage

V0.2 x V

BATT

V

IL

SHDN Input Low Voltage

µA0.01 1PFO Leakage Current

V0.04 0.4V

OL

PFO Low Output Voltage

nA0.1 10PFI Input Current

mV590 614 632V

IL,PFI

PFI Trip Voltage

nA0.1 10FB Input Current

%90

η

Efficiency

µA2 3.5I

SHDN,BATT

Shutdown Current into BATT

µA0.1 1I

SHDN,OUT

Shutdown Current into OUT

µA4 8I

Q,BATT

Quiescent Current into BATT

µA37 65I

Q,OUT

Quiescent Current into OUT

V-µs5.60 8 11.2KOn-Time Constant

V0.87Start-Up Voltage (Note 2)

V5.5V

BATT(MAX)

V0.7V

BATT(MIN)

Minimum Operating Input
Voltage

Maximum Operating Input
Voltage

mA550I

LX(MAX)

Maximum Peak LX Current

V0.8P-Channel Catch Diode Voltage

Ω1.5 2.2P-Channel On-Resistance

Ω1 1.5N-Channel On-Resistance

mV/°C-2Start-Up Voltage Tempco

V3.16 3.3 3.44V

OUT

Output Voltage (Fixed Mode)

V2.0 5.5

Output Voltage Range
(Adjustable Mode)

V1.19 1.23 1.26V

FB

FB Set Voltage

UNITSMIN TYP MAXSYMBOLPARAMETER

SHDN = GND or BATT

nA0.1 10

SHDN Input Current

MAX1678

1-Cell to 2-Cell, Low-Noise,

High-Efficiency, Step-Up DC-DC Converter

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS

(V

BATT

= V

SHDN

= 1.3V, I

LOAD

= 0, FB = GND, TA= -40°C to +85°C, unless otherwise noted.) (Note 3)

V

PFI

= 650mV, V

PFO

= 6V

V

PFI

= 0, V

OUT

= 3.3V, I

SINK

= 1mA

V

PFI

= 650mV

Falling PFI hysteresis 2%

VFB= 1.3V

V

BATT

= 1V

V

OUT

= 3.5V

V

OUT

= 3.3V

V

OUT

= 3.3V

VFB< 0.1V
External feedback

V

OUT

= 3.5V

External feedback

0.9V < V

BATT

< 3.3V (tON= K / V

BATT

)

CONDITIONS

V0.8 x V

BATT

V

IH

SHDN Input High Voltage

V0.2 x V

BATT

V

IL

SHDN Input Low Voltage

µA1PFO Leakage Current

V0.4V

OL

PFO Low Output Voltage

nA10PFI Input Current

mV580 642V

IL,PFI

PFI Trip Voltage

nA10FB Input Current

µA3.5I

SHDN,BATT

Shutdown Current into BATT

µA1I

SHDN,OUT

Shutdown Current into OUT

µA8I

Q,BATT

Quiescent Current into BATT

µA65I

Q,OUT

Quiescent Current into OUT

V-µs5.60 11.2KOn-Time Constant

V5.5V

BATT(MAX)

Maximum Operating Input
Voltage

Ω2.2P-Channel On-Resistance

Ω1.5N-Channel On-Resistance

V3.12 3.48V

OUT

Output Voltage (Fixed Mode)

V2.0 5.5

Output Voltage Range
(Adjustable Mode)

V1.17 1.28V

FB

FB Set Voltage

UNITSMIN MAXSYMBOLPARAMETER

SHDN = GND or BATT

nA10

SHDN Input Current

Note 2: Start-up is guaranteed by correlation to measurements of device parameters (i.e., switch on-resistance, on-time, off-time,

and output voltage trip point).

Note 3: Specifications to -40°C are guaranteed by design and not production tested.

MAX1678

1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter

4 _______________________________________________________________________________________

Typical Operating Characteristics

(Circuit of Figure 7 (Fixed Mode, 3.3V) or Figure 8 (Adjustable Mode), TA= +25°C, unless otherwise noted.)

100

0

0.01 0.1 1 10 100

200

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 2.4V, L1 = 22µH)

20

MAX1678-01

LOAD CURRENT (mA)

EFFICIENCY (%)

40

60

80

90

70

50

30

10

VIN = 2.0V

VIN = 1.5V

L1 = 22µH
SUMIDA CD43-220
R1 = 200kΩ, R2 = 200kΩ

VIN = 1.2V

VIN = 0.85V

100

0

0.01 0.1 1 10 100

200

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 2.4V, L1 = SUMIDA 47µH)

20

MAX1678-02

LOAD CURRENT (mA)

EFFICIENCY (%)

40

60

80

90

70

50

30

10

VIN = 2.0V

VIN = 1.5V

L1 = 47µH
SUMIDA CD43-470
R1 = 200kΩ, R2 = 200kΩ

VIN = 1.2V

VIN = 0.85V

100

0

0.01 0.1 1 10 100

200

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 2.4V, L1 = TDK 47µH)

20

MAX1678-03

LOAD CURRENT (mA)

EFFICIENCY (%)

40

60

80

90

70

50

30

10

VIN = 2.0V

VIN = 1.5V

L1 = 47µH
TDK NLC453232T-470K
R1 = 200kΩ, R2 = 200kΩ

VIN = 1.2V

VIN = 0.85V

100

0

0.01 0.1 1 10 100

200

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 3.3V, L1 = 22µH)

20

MAX1678-04

LOAD CURRENT (mA)

EFFICIENCY (%)

40

60

80

90

70

50

30

10

VIN = 2.5V

VIN = 2.0V

L1 = 22µH
SUMIDA CD43-220
FB = GND

VIN = 1.5V

VIN = 1.2V

VIN = 0.85V

100

0

0.01 0.1 1 10 100

200

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 5.0V, L1 = 22µH)

20

MAX1678-07

LOAD CURRENT (mA)

EFFICIENCY (%)

40

60

80

90

70

50

30

10

VIN = 4.5V

VIN = 2.0V

L1 = 22µH
SUMIDA CD43-220
R1 = 619kΩ, R2 = 200kΩ

VIN = 3.0V

VIN = 1.2V

VIN = 0.85V

100

0

0.01 0.1 1 10 100

200

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 3.3V, L1 = SUMIDA 47µH)

20

MAX1678-05

LOAD CURRENT (mA)

EFFICIENCY (%)

40

60

80

90

70

50

30

10

VIN = 2.5V

VIN = 2.0V

L1 = 47µH
SUMIDA CD43-470
FB = GND

VIN = 1.5V

VIN = 1.2V

VIN = 0.85V

100

0

0.01 0.1 1 10 100

200

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 3.3V, L1 = TDK 47µH)

20

MAX1678-06

LOAD CURRENT (mA)

EFFICIENCY (%)

40

60

80

90

70

50

30

10

VIN = 2.5V

VIN = 2.0V

L1 = 47µH
TDK NLC453232T-470K
FB = GND

VIN = 1.5V

VIN = 1.2V

VIN = 0.85V

100

0

0.01 0.1 1 10 100

200

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 5.0V, L1 = SUMIDA 47µH)

20

MAX1678-08

LOAD CURRENT (mA)

EFFICIENCY (%)

40

60

80

90

70

50

30

10

VIN = 4.5V

VIN = 3.0V

L1 = 47µH
SUMIDA CD43-470
R1 = 619kΩ, R2 = 200kΩ

VIN = 2.0V

VIN = 1.2V

VIN = 0.85V

100

0

0.01 0.1 1 10 100

200

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 5.0V, L1 = TDK 47µH)

20

MAX1678-09

LOAD CURRENT (mA)

EFFICIENCY (%)

40

60

80

90

70

50

30

10

VIN = 4.5V

VIN = 3.0V

L1 = 47µH
TDK NLC453232-470K
R1 = 619kΩ, R2 = 200kΩ

VIN = 2.0V

V

IN

= 1.2V

V

IN

= 0.85V