Maxim MAX629C-D, MAX629ESA Datasheet

_______________General Description

The MAX629 low-power DC-DC converter features an
internal N-channel MOSFET switch and programmable
current limiting. It is designed to supply positive or neg­ative bias voltages up to ±28V from input voltages in
the 0.8V to V

OUT

range, and can be configured for

boost, flyback, and SEPIC topologies.
The MAX629’s current-limited pulse-frequency-modula-

tion (PFM) control scheme provides high efficiency over
a wide range of load conditions. An internal, 0.5A N­channel MOSFET switch reduces the total part count,
and a high switching frequency (up to 300kHz) allows
for tiny surface-mount magnetics.

The MAX629’s combination of low supply current, logic­controlled shutdown, small package, and tiny external
components makes it an extremely compact and effi­cient high-voltage biasing solution that’s ideal for bat­tery-powered applications. The MAX629 is available in
an 8-pin SO package.

________________________Applications

Positive or Negative LCD Bias Generators
High-Efficiency DC-DC Boost Converters
Varactor Tuning Diode Bias
Palmtop Computers
2-Cell and 3-Cell Battery-Powered Applications

____________________________Features

♦ Internal, 500mA, 28V N-Channel Switch

(No External FET Required)

♦ Generates Positive or Negative Output Voltages
♦ 80µA Supply Current
♦ 1µA Max Shutdown Current
♦ Up to 300kHz Switching Frequency
♦ Adjustable Current Limit Allows Use of Small,

Inexpensive Inductors

♦ 8-Pin SO Package

MAX629

28V, Low-Power, High-Voltage,

Boost or Inverting DC-DC Converter

________________________________________________________________

Maxim Integrated Products

1

MAX629

SHDN

V

IN

+2.7V

TO +5.5V

LX

V

CC

GND

FB

ISET
POL

REF

POSITIVE OUTPUT VOLTAGE

MAX629

SHDN

-V

OUT

-28V

V

OUT

28V

V

IN

+2.7V

TO +5.5V

LX

V

CC

GND

FB

REF

POL

NEGATIVE OUTPUT VOLTAGE

ISET

___________________________________________________Typical Operating Circuit

19-1219; Rev 1; 6/97

PART TEMP. RANGE PIN-PACKAGE

______________Ordering Information

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone]

Note: To order tape-and-reel shipping, add “-T” to the end of

the part number.

*

Dice are tested at TA= +25°C, DC parameters only.

Pin Configuration appears at end of data sheet.

MAX629C/D 0°C to +70°C Dice*
MAX629ESA -40°C to +85°C 8 SO

EVALUATION KIT MANUAL

AVAILABLE

MAX629

28V, Low-Power, High-Voltage,
Boost or Inverting DC-DC Converter

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +5V, C

REF

= 0.1µF, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note1)

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.

Supply Voltage (VCCto GND)..................................-0.3V to +6V

SHDN to GND...........................................................-0.3V to +6V

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

CC

+ 0.3V)

LX to GND ..............................................................-0.3V to +30V

Continuous Power Dissipation (T

A

= +70°C)

SO (derate 5.88mW/°C above +70°C)..........................471mW

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

CONDITIONS

V2.7 5.5VCCInput Voltage (Note 2)

UNITSMIN TYP MAXPARAMETER

VFB= 1.3V µA80 120VCCSupply Current

100mV hysteresis V2.3 2.5 2.65VCCUndervoltage Lockout

SHDN = GND

µA0.04 1VCCShutdown Current

A

0.39 0.45 0.51

Circuit of Figure 2

VLX= 28V, TA= +85°C µA0.05 2.5LX Leakage Current

POL = GND

µs

0.7 1.0 1.3

Minimum LX Off-Time

µs6.5 8.5 10.0Maximum LX On-Time

0.20 0.25 0.33

LX Switch-Current Limit

V28Positive Output Voltage

POL = GND, VFB< 1V 3.0 4.5 6.0

POL = V

CC

2.0 3.2 3.8

POL = GND
(positive output)

V

1.218 1.282

1.225 1.250 1.275

nA5 50FB Input Bias Current

1.225 1.250 1.275

VCC= 5V

Ω

0.6 1.2

VCC= 3.3V 0.7 1.4

LX On-Resistance

TA= 0°C to +85°C
TA= -40°C to +85°C
TA= 0°C to +85°C
TA= -40°C to +85°C

POL = V

CC

(negative output)

mV

-25 25

FB Set Point

-15 0 15

VCC= 2.7V to 5.5V,
no load on REF

V

1.218 1.282

REF Output Voltage

TA= 0°C to +85°C
TA= -40°C to +85°C

V

IH

V

2.4

SHDN, POL, ISET Logic Levels

V

IL

0.4

Voltage applied to L1 (VIN) V

0.8



V

OUT



Input Supply Voltage (Note 2)

Circuit of Figure 3 V

-V

IN

-28

Negative Output Voltage

ISET = V

CC

ISET = GND

POL = V

CC, VFB

> 0.25V 3.0 4.5 6.0

MAX629

28V, Low-Power, High-Voltage,

Boost or Inverting DC-DC Converter

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +5V, C

REF

= 0.1µF, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

Note 1: Specifications to -40°C are guaranteed by design and not production tested.
Note 2: The IC itself requires a supply voltage between +2.7V and +5.5V; however, the voltage that supplies power to the inductor

can vary from 0.8V to 28V, depending on circuit operating conditions.

Note 3: For reference currents less than 10µA, a 0.1µF reference-bypass capacitor is adequate.

Circuit of Figure 2, V

OUT

= 24V, VCC= 3V to 5.5V,

I

LOAD

= 5mA

%/V0.2Line Regulation

Die temperature °C150

I

REF

= 0µA to 100µA, C

REF

= 0.47µF (Note 3)

Thermal Shutdown Threshold

Circuit of Figure 2, V

OUT

= 24V, VCC= 5V,

I

LOAD

= 0mA to 5mA

%0.15Load Regulation

CONDITIONS

mV10 25REF Load Regulation

UNITSMIN TYP MAXPARAMETER

__________________________________________Typical Operating Characteristics

(SHDN = VCC, C

REF

= 0.1µF, TA= +25°C, unless otherwise noted.)

100

60

0.1 100

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= +24V)

65

70

95
90
85

MAX629-01

LOAD CURRENT (mA)

EFFICIENCY (%)

1 10

80
75

D

D: VIN = 5V, ISET = GND
E: V

IN

= 3V, ISET = V

CC

F: VIN = 3V, ISET = GND

V

OUT

= 24V

A: V

IN

= 12V, ISET = V

CC

B: VIN = 12V, ISET = GND
C: V

IN

= 5V, ISET = V

CC

E, F

C

B

A

100

60

0.1 100

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= +12V)

70
65

95

85

90

MAX629-02

LOAD CURRENT (mA)

EFFICIENCY (%)

1 10

80
75

C

B

A

V

OUT

= 12V,

ISET = V

CC

or GND

A: V

IN

= 9V

B: V

IN

= 5V

C: V

IN

= 3V

300

0

0 20

MAXIMUM LOAD CURRENT vs.

INPUT VOLTAGE (V

OUT

= +24V, +12V)

50

250

200

MAX629-03

INPUT VOLTAGE (V)

MAXIMUM LOAD CURRENT (mA)

8 124 16

150

100

A

B

C

D

A: V

OUT

= 12V,

ISET = V

CC

B: V

OUT

= 12V,

ISET = GND

C: V

OUT

=24V,

ISET = V

CC

D: V

OUT

= 24V,

ISET = GND

100

50

0.1 100

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= -18V)

65
60
55

95

80

85

90

MAX629-04

LOAD CURRENT (mA)

EFFICIENCY (%)

1 10

75
70

C

A

A: VIN = 12V, ISET = V

CC

B: VIN = 12V, ISET = GND
C: V

IN

= 5V, ISET = VCC or GND

D: V

IN

= 3V, ISET = VCC or GND

B

D

100

50

0.1 100

EFFICIENCY vs. LOAD CURRENT

(V

OUT

= -12V)

65
60
55

95

80

85

90

MAX629-05

LOAD CURRENT (mA)

EFFICIENCY (%)

1 10

75
70

A

A = VIN = 5V, ISET = V

CC

B = VIN = 5V, ISET = GND
C = V

IN

= 3V, ISET = VCC

D = V

IN

= 3V, ISET = GND

D

B, C

90

0

0 20

MAXIMUM LOAD CURRENT vs. INPUT VOLTAGE

(V

OUT

= -18V, -12V)

30
20
10

80

60

70

MAX629-06

INPUT VOLTAGE (V)

MAXIMUM LOAD CURRENT (mA)

4 8 12 16

50
40

C

A

A: V

OUT

= -12V, ISET = V

CC

B: V

OUT

= -18V, ISET = V

CC

C: V

OUT

= -12V, ISET = GND

D: V

OUT

= -18V, ISET = GND

D

B

MAX629

28V, Low-Power, High-Voltage,
Boost or Inverting DC-DC Converter

4 _______________________________________________________________________________________

700

600

0

0 1

SUPPLY CURRENT

vs. INPUT VOLTAGE

500

400

300

100

MAX629-07

INPUT VOLTAGE (V)

SUPPLY CURRENT (µA)

2 3 4 5

200

VIN = V

CC

I

CC

I

IN

I

IN

1.255

1.250

1.230
0 20 40

REFERENCE VOLTAGE

vs. REFERENCE LOAD CURRENT

1.245

1.240

MAX629-08

REFERENCE LOAD CURRENT (µA)

REFERENCE VOLTAGE (V)

60 80 100 120 140 160

1.235

VIN = V

CC

= 5V

C4 = 0.47µF

OUTPUT VOLTAGE RIPPLE

MAX629-09

V

OUT

= +24V, I

LOAD

= 5mA

A: ISET = V

CC

, 20mV/div

B: ISET = GND, 20mV/div

A

B

10µs/div

SHUTDOWN TRANSIENT

(POSITIVE CONFIGURATION)

MAX629-12

VCC = VIN = 5V, RL = 4kΩ

50ms/div

5V

SHDN

0V

24V

V

OUT

0V

LOAD-TRANSIENT RESPONSE

(I

SET

= VCC, I

LIM

= 500mA)

MAX629-10

V

OUT

= +24V, ISET = V

CC

A: LOAD CURRENT, 0mA TO 5mA, 2.5mA/div
B: V

OUT,

AC-COUPLED, 10mV/div

A

5mA

0mA

B

200µs/div

LOAD-TRANSIENT RESPONSE

(I

SET

= GND, I

LIM

= 250mA)

MAX629-11

V

OUT

= +24V, ISET = GND
A: LOAD CURRENT, 0mA TO 5mA, 2.5mA/div
B: V

OUT,

AC-COUPLED, 10mV/div

A

0mA

5mA

B

100µs/div

SHUTDOWN TRANSIENT

(NEGATIVE CONFIGURATION)

MAX629-13

START-UP DELAY, VCC = VIN = 5V, I

LOAD

= 5mA

20ms/div

VCC = VIN = 5V, RL = 4kΩ

50ms/div

5V

0V

0V

V

OUT

-20V

SHDN

____________________________Typical Operating Characteristics (continued)

(SHDN = VCC, C

REF

= 0.1µF, TA= +25°C, unless otherwise noted.)