Maxim MAX1685EEE Datasheet

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General Description

The MAX1684/MAX1685 are high-efficiency, internal­switch, PWM step-down switching regulators intended to
power cellular phones, communicating PDAs, and
handy-terminals. These devices deliver a guaranteed 1A
output current from two Li-Ion batteries. Their wide input
voltage range of 2.7V to 14V gives design flexibility and
allows batteries to charge from a wall cube, since the ICs
operate at the higher voltages that occur when the bat­tery is removed. The output voltage is preset to 3.3V or
can be externally adjusted from 1.25V to VIN.

The low-on-resistance power switch and built-in synchro­nous rectifier provide high efficiencies of up to 96%.
There are four modes of operation: fixed-frequency
mode, normal mode, low-power mode, and shutdown
mode. The fixed-frequency PWM mode of operation
offers excellent noise characteristics. The normal mode
maintains high efficiency at all loads. The low-power
mode is used to conserve power in standby or when full
load is not required. The shutdown mode is used to
power down the device for minimal current draw.

The MAX1684 runs at 300kHz for applications that
require highest efficiency. The MAX1685 runs at
600kHz to allow use of smaller external components.
These devices can also be synchronized to an external
clock. Other features include a 100% duty cycle for
low-dropout applications, an auxiliary 3V/5mA output,
and a 1% accurate reference.

Both devices are available in a space-saving 16-QSOP
package. An evaluation kit is also available to help
speed designs. For a similar device in a 10-pin µMAX
package with lower input voltage requirements (5.5V
max), see the MAX1692 data sheet.

Applications

Cellular Phones
2-Way Radios and Walkie-Talkies
Computer Peripherals
Personal Communicators
PDAs and Handy-Terminals

Features

♦ Up to 96% Efficiency
♦ 1A Guaranteed Output Current
♦ 100% Duty Cycle in Dropout
♦ 2.7V to 14V Input Range (15V absolute max)
♦ ±1% Accurate Reference Output
♦ 0.24Ω P-Channel On-Resistance
♦ Synchronizable Switching Frequency
♦ Fixed-Frequency PWM Operation

300kHz (MAX1684)
600kHz (MAX1685)

♦ 150µA Normal Mode Quiescent Current
♦ 25µA Low-Power Mode Quiescent Current
♦ 2µA Shutdown Current
♦ Dual Mode™ Fixed 3.3V (±1%) Output or

Adjustable Output (1.25V to V

IN

)

♦ Small 16-QSOP Package
♦ Auxiliary Output (CVL): 3V/5mA

MAX1684/MAX1685

Low-Noise, 14V Input, 1A, PWM

Step-Down Converters

________________________________________________________________

Maxim Integrated Products

1

MAX1684
MAX1685

LXIN

AIN

GND

OUTPUT

3.3V AT 1A

INPUT

2.7V TO 14V

BOOT

SHDN

CVH
CVL
STBY
SYNC/PWM

FB CC REF

+

+

19-1454; Rev 0; 4/99

PART

MAX1684EEE
MAX1685EEE

-40°C to +85°C

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

16 QSOP
16 QSOP

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

Typical Operating Circuit

Ordering Information

Pin Configuration appears at end of data sheet.

Dual Mode is a trademark of Maxim Integrated Products.

MAX1684/MAX1685

Low-Noise, 14V Input, 1A, PWM
Step-Down Converters

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= V

SHDN

= +6V, STBY = SYNC/PWM = CVL, V

BOOT

= V

OUT

, FB = AGND, circuit of Figure 1, TA= 0°C to +85°C, unless other-

wise noted. Typical values are at T

A

= +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.

AIN to AGND ............................................................-0.3 to +15V

IN to PGND................................................-0.3V to (V

AIN

+ 0.3V)

LX to PGND .................................................-0.5V to (V

IN

+ 0.3V)

PGND to AGND ..................................................................±0.3V

SHDN to AGND .........................................-0.3V to (V

AIN

+ 0.3V)

ILIM/SS, FB, CC, BOOT, REF to AGND.....-0.3V to (V

CVL

+ 0.3V)

CVH to IN..................................................................-6V to +0.3V

CVL, STBY, SYNC/PWM to AGND............................-0.3V to +6V

Reference Current..............................................................±1mA

CVL Current ..........................................................10mA to -1mA

LX Peak Current (Internally Limited).....................................2.3A

Continuous Power Dissipation (T

A

= +70°C)

16-Pin QSOP (derate 8.3mW/°C above +70°C)............667mW

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

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

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

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

V

FB

= V

OUT

, I

LOAD

= 0 to 1A

Low-power mode, STBY = low,
V

BOOT

= 3.3V (Note 2)

Normal mode, SYNC/PWM = low,
V

BOOT

= 3.3V (Note 2)

PWM mode,
SYNC/PWM = high,
V

BOOT

= 3.3V

(Note 2)

SYNC/PWM = high

Low-side switch, VIN= 2.7V, ILX= 200mA

High-side switch,
ILX= 1A

VFB= V

OUT

, I

LOAD

= 0 to 1A
VIN= 5V to 14V
BOOT = AGND (Note 1)

SYNC/PWM = low

VFB= 1.4V

CONDITIONS

0.14 0.27

Quiescent Power Consumption

0.9 2

25 65

mW

13 33

mA

40 80 120

Zero Crossing Threshold

20 50 80

VV

FB

Feedback Voltage 1.238 1.251 1.264

V2.7 14Input Voltage Range

A0.15 0.4 0.9Current Limit, N-Channel

A1.2 1.75 2.3I

LIM

Current Limit in PWM Mode

Ω38On-Resistance, N-Channel

0.24 0.5

%0.01Output Load Regulation

A1Output Current Capability
VV

REF

V

IN

Output Adjust Range

nA-50 50I

FB

FB Input Current

UNITSMIN TYP MAXSYMBOLPARAMETER

FB = AGND, I

LOAD

= = 0 to 1A VV

OUT

Output Voltage (3.3V mode) 3.3 3.333 3.365

VIN= 6V
VIN= 2.7V

Ω

0.34 0.8

On-Resistance, P-Channel

MAX1684
MAX1685

MAX1684

MAX1685

SYNC/PWM = low mA285 380 475Pulse-Skipping Current Threshold
STBY = low

mA285 380 475I

LIMLP

Current Limit in Low-Power
Mode

MAX1684/MAX1685

Low-Noise, 14V Input, 1A, PWM

Step-Down Converters

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= V

SHDN

= +6V, STBY = SYNC/PWM = CVL, V

BOOT

= V

OUT

, FB = AGND, circuit of Figure 1, TA= 0°C to +85°C, unless other-

wise noted. Typical values are at T

A

= +25°C.)

STBY = low, VIN= 2.7V

CONDITIONS

µA230 430

Quiescent Supply Current
in Dropout

UNITSMIN TYP MAXSYMBOLPARAMETER

SHDN = low

µA26Shutdown Supply Current

MAX1684 260 300 340

MAX1684 180 350

VIN= 14V, VLX= 0 or 14V, SHDN = low

SYNC Capture Range

MAX1685

kHz

520 600 680

f

OSC

Oscillator Frequency

µA20I

LX

LX Leakage Current

%100Maximum Duty Cycle

(Note 3) %

20

MAX1685

Constant-Frequency Minimum
Duty Cycle

10

-1µA < I

REF

< 50µA mV415Reference Load Regulation

VIN= 3V to 14V, BOOT = AGND,
I

CVL

= 0 to 5mA

V2.7 3.0 3.15

I

REF

= 0

CVL Regulator Output Voltage

2.7V < V

BOOT

< 5.5V mV0.2 5Reference Supply Regulation

V1.238 1.251 1.264V

REF

Reference Output Voltage

kHz

360 700

MAX1684
MAX1685

BOOT = AGND, I

CVL

= 5mA mV120CVL Dropout Voltage

Typical hysteresis is 10°C (Note 4) °C160Thermal Shutdown Threshold

BOOT falling edge,
typical hysteresis is 0.1V

V2.4 2.5 2.6BOOT Switchover Threshold

I

CVH

= -1mA V-5.0 -4.6 -4.1CVH with Respect to V

IN

SHDN, STBY, SYNC/PWM

V2V

IH

Logic Input High Voltage

V

ILIM/SS

= 1.4V µA3.3 4 4.65ILIM/SS Source Current

High or low period ns500SYNC/PWM Pulse Width

SHDN, STBY, SYNC/PWM

µA-1 1Logic Input Current

0.7V

IL

Logic Input Low Voltage

BOOT = AGND, CVL falling edge,
typical hysteresis is 40mV

V2.4 2.5 2.6

CVL Undervoltage Lockout
Threshold

V

MAX1684/MAX1685

Low-Noise, 14V Input, 1A, PWM
Step-Down Converters

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

(VIN= V

SHDN

= +6V, STBY = SYNC/PWM = CVL, V

BOOT

= V

OUT

, FB = AGND, circuit of Figure 1, TA= -40°C to +85°C, unless other-

wise noted.) (Note 5)

Note 1: The output adjust range with BOOT connected to V

OUT

is V

REF

to 5.5V. Connect BOOT to AGND for V

OUT

> 5.5V.

Note 2: The quiescent power-consumption specifications include chip supply and gate-drive loss only. Divide these values by V

IN

(= 6V) to obtain quiescent currents. In normal and low-power modes, chip supply current dominates and quiescent power
is proportional to V

BOOT

(BOOT connected to OUT). In PWM mode, gate-drive loss dominates and quiescent power is pro-

portional to V

IN

· (V

IN

- V

CVH

). In addition, IR losses in power switches and external components typically increase PWM
quiescent power consumption by 5mW to 10mW. Note that if the device is not bootstrapped, additional power will be dissi­pated in the CVL linear regulator.

Note 3: When the duty factor (V

OUT

/ VIN) is less than this value, the switching frequency decreases in PWM mode to maintain regu-

lation.

Note 4: Thermal shutdown is disabled in low-power mode (STBY = low) to reduce power consumption.
Note 5: Specifications to -40°C are guaranteed by design, not production tested.

CVL Undervoltage Lockout
Threshold

2.4 2.6 V

BOOT = AGND, CVL falling edge,
typical hysteresis is 40mV

Logic Input Low Voltage V

IL

0.7

Logic Input High Voltage V

IH

2

V

SHDN, STBY, SYNC/PWM

ILIM/SS Source Current 3.1 4.7 µAV

ILIM/SS

= 1.4V

0.27

Normal mode, SYNC/PWM = low,
V

BOOT

= 3.3V (Note 2)

BOOT Switchover Threshold 2.4 2.6 VBOOT falling edge, typical hysteresis is 0.1V

CVH with Respect to V

IN

-5.0 -4.1 VI

CVH

= -1mA

CVL Regulator Output Voltage 2.7 3.15 V

VIN= 3V to 14V, BOOT = AGND,
I

CVL

= 0 to 5mA

Reference Output Voltage 1.236 1.266 VI

REF

= 0

Oscillator Frequency f

OSC

480 700

kHz

MAX1685

240 350MAX1684

Shutdown Supply Current 6 µA

SHDN = low

Quiescent Power Consumption

2

mW

Current Limit in Low-Power
Mode

I

LIMLP

285 475 mA

STBY = low

Output Voltage (3.3V mode) V

OUT

3.295 3.375 V

PARAMETER SYMBOL MIN MAX UNITS

FB Input Current I

FB

-50 50 nA

Output Adjust Range V

REF

V

IN

V

Output Current Capability 1 A

Input Voltage Range 2.7 14 V
Output Feedback Voltage V

FB

1.236 1.266 V

Current Limit in PWM Mode I

LIM

1.2 2.3 A

CONDITIONS

VFB= 1.4V

BOOT = AGND (Note 1)

VIN= 6V to 14V

FB = AGND, I

LOAD

= = 0 to 1A

VFB= V

OUT

, I

LOAD

= 0 to 1A

Low-power mode, STBY = low,
V

BOOT

= 3.3V (Note 2)

MAX1684/MAX1685

Low-Noise, 14V Input, 1A, PWM

Step-Down Converters

_______________________________________________________________________________________

5

100

0

0.1 1 10 100 1,000 10,000

MAX1684
EFFICIENCY vs. LOAD CURRENT
(V

IN

= 3.3V, V

OUT

= 1.8V, 2.5V)

20

10

MAX1684/85-01

LOAD CURRENT (mA)

EFFICIENCY (%)

40

30

60

80

90

70

50

A: V

OUT

= 2.5V LP MODE

B: V

OUT

= 1.8V LP MODE

C: V

OUT

= 2.5V NORM MODE

D: V

OUT

= 1.8V NORM MODE

E: V

OUT

= 2.5V PWM MODE

F: V

OUT

= 1.8V PWM MODE

A

D

E

B

F

C

100

0

0.1 1 10 100 1,000 10,000

MAX1684

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 3.3V)

20
10

MAX1684/85-02

LOAD CURRENT (mA)

EFFICIENCY (%)

40
30

60

80

90

70

50

A: VIN = 4V LOW-POWER MODE
B: V

IN

= 12V LOW-POWER MODE

C: V

IN

= 4V NORMAL MODE

D: V

IN

= 12V NORMAL MODE

D

C

A

B

1 10010 1,000 10,000

MAX1684

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 3.3V, PWM MODE)

MAX1684/85-03

LOAD CURRENT (mA)

EFFICIENCY (%)

100

0

20

10

50
40
30

70
60

90
80

A: VIN = 4V
B: V

IN

= 5V

C: V

IN

= 9V

D: V

IN

= 12V

C

B

A

D

100

20

0.1 1 10 100 1,000 10,000

MAX1684

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 5V)

40
30

MAX1684/85-04

LOAD CURRENT (mA)

EFFICIENCY (%)

50

70

90
80

60

A: VIN = 6V LP MODE

B: V

IN

= 9V LP MODE

C: V

IN

= 12V LP MODE

D: V

IN

= 6V NORMAL MODE

E: V

IN

= 9V NORMAL MODE

F: V

IN

= 12V NORMAL MODE

E

B

F

E

D

A

C

100

0

0.1 1 10 100 1,000 10,000

MAX1685

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 3.3V)

20
10

MAX1684/85-07

LOAD CURRENT (mA)

EFFICIENCY (%)

40
30

60

80

90

70

50

A: VIN = 4V LP MODE
B: V

IN

= 12V LP MODE

C: V

IN

= 4V NORMAL MODE

D: V

IN

= 12V NORMAL MODE

D

C

B

A

1 10010 1,000 10,000

MAX1684

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 5V, PWM MODE)

MAX1684/85-05

LOAD CURRENT (mA)

EFFICIENCY (%)

100

0

20

10

50
40
30

70
60

90
80

A: VIN = 6V
B: V

IN

= 9V

C: V

IN

=12V

C

B

A

1 10010 1,000 10,000

MAX1685

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 3.3V, PWM MODE)

MAX1684/85-06

LOAD CURRENT (mA)

EFFICIENCY (%)

100

0

20

10

50
40
30

70
60

90
80

VIN = 5V

VIN =9V

VIN = 12V

VIN = 4V

1 10010 1,000 10,000

MAX1685

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 5V PWM MODE)

MAX1684/85-08

LOAD CURRENT (mA)

EFFICIENCY (%)

100

0

20
10

50
40
30

70
60

90
80

VIN = 6V

VIN = 9V

VIN =12V

100

0

0.1 1 10 100 1,000 10,000

MAX1685

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= 5V)

20
10

MAX1684/85-09

LOAD CURRENT (mA)

EFFICIENCY (%)

40
30

60

80

90

70

50

A: VIN = 6V LOW-POWER MODE
B: V

IN

= 9V LOW-POWER MODE

C: V

IN

= 12V LOW-POWER MODE

D: V

IN

= 6V NORMAL MODE

E: V

IN

= 9V NORMAL MODE

F: V

IN

=12V NORMAL MODE

A

F

E

D

C

B

Typical Operating Characteristics

(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)