MAXIM MAX1846, MAX1847 User Manual

General Description

MAX1846/MAX1847 high-efficiency PWM inverting con­trollers allow designers to implement compact, low­noise, negative-output DC-DC converters for telecom
and networking applications. Both devices operate
from +3V to +16.5V input and generate -2V to -200V
output. To minimize switching noise, both devices fea­ture a current-mode, constant-frequency PWM control
scheme. The operating frequency can be set from
100kHz to 500kHz through a resistor.

The MAX1846 is available in an ultra-compact 10-pin
µMAX package. Operation at high frequency, compati­bility with ceramic capacitors, and inverting topology
without transformers allow for a compact design.
Compatibility with electrolytic capacitors and flexibility
to operate down to 100kHz allow users to minimize the
cost of external components. The high-current output
drivers are designed to drive a P-channel MOSFET and
allow the converter to deliver up to 30W.

The MAX1847 features clock synchronization and shut­down functions. The MAX1847 can also be configured
to operate as an inverting flyback controller with an N­channel MOSFET and a transformer to deliver up to
70W. The MAX1847 is available in a 16-pin QSOP
package.

Current-mode control simplifies compensation and pro­vides good transient response. Accurate current-mode
control and over current protection are achieved
through low-side current sensing.

Applications

Cellular Base Stations

Networking Equipment

Optical Networking Equipment

SLIC Supplies

CO DSL Line Driver Supplies

Industrial Power Supplies

Automotive Electronic Power Supplies

Servers

Features

♦ 90% Efficiency

♦ +3.0V to +16.5V Input Range

♦ -2V to -200V Output

♦ Drives High-Side P-Channel MOSFET

♦ 100kHz to 500kHz Switching Frequency

♦ Current-Mode, PWM Control

♦ Internal Soft-Start

♦ Electrolytic or Ceramic Output Capacitor

♦ The MAX1847 also offers:

Synchronization to External Clock
Shutdown
N-Channel Inverting Flyback Option

MAX1846/MAX1847

High-Efficiency, Current-Mode,

Inverting PWM Controller

________________________________________________________________ Maxim Integrated Products 1

Typical Operating Circuit

19-2091; Rev 0; 8/01

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Ordering Information

Pin Configurations appear at end of data sheet.

PART TEMP. RANGE PIN-PACKAGE

MAX1846EUB -40°C to +85°C 10 µMAX

MAX1847EEE -40°C to +85°C 16 QSOP

POSITIVE

V

IN

P

VL IN

EXT

COMP

MAX1846
MAX1847

CS

FREQ

PGND

REF

GND

FB

NEGATIVE

V

OUT

MAX1846/MAX1847

High-Efficiency, Current-Mode,
Inverting PWM Controller

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

SHDN

= VIN= +12V, SYNC = GND, PGND = GND, R

FREQ

= 147kΩ ±1%, C

VL

= 0.47µF, C

REF

= 0.1µF, 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.

IN, SHDN to GND...................................................-0.3V to +20V

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

VL to PGND for V

IN

≤ 5.7V...........................-0.3V to (VIN+ 0.3V)

VL to PGND for V

IN

> 5.7V .......................................-0.3V to +6V

EXT to PGND ...............................................-0.3V to (V

IN

+ 0.3V)

REF, COMP to GND......................................-0.3V to (VL + 0.3V)

CS, FB, FREQ, POL, SYNC to GND .........................-0.3V to +6V

Continuous Power Dissipation (T

A

= +70°C)

10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW

16-Pin QSOP (derate 8.3mW/°C above +70°C)...........696mW

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

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

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

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

PARAMETER CONDITIONS MIN TYP MAX UNITS
PWM CONTROLLER
Operating Input Voltage Range 3.0 16.5 V

V

rising 2.8 2.95

UVLO Threshold

IN

VIN falling 2.6 2.74

UVLO Hysteresis 60 mV
FB Threshold No load -12 0 12 mV
FB Input Current V

Load Regulation

Line Regulation

= -0.1V -50 -6 50 nA

FB

C

= 0.068µF, V

COMP

I

= 20mA to 200mA (Note 1)

OUT

C

= 0.068µF, V

COMP

V

= +8V to +16.5V, I

IN

OUT

OUT

OUT

= -48V,

= -48V,

= 100mA

Current-Limit Threshold 85 100 115 mV
CS Input Current CS = GND 10 20 µA
Supply Current V
Shutdown Supply Current

= -0.1V, VIN = +3.0V to +16.5V 0.75 1.2 mA

FB

SHDN = GND, V

= +3.0V to +16.5V

IN

REFERENCE AND VL REGULATOR
REF Output Voltage I
REF Load Regulation I
VL Output Voltage I
VL Load Regulation I

= 50µA 1.236 1.25 1.264 V

REF

= 0 to 500µA -2 -15 mV

REF

= 100µA 3.85 4.25 4.65 V

VL

= 0.1mA to 2.0mA -20 -60 mV

VL

-1 0 %

0.04 %

10 25 µA

V

MAX1846/MAX1847

High-Efficiency, Current-Mode,

Inverting PWM Controller

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

SHDN

= VIN= +12V, SYNC = GND, PGND = GND, R

FREQ

= 147kΩ ±1%, C

VL

= 0.47µF, C

REF

= 0.1µF, TA= 0°C to +85°C, unless

otherwise noted.)

Note 1: Production test correlates to operating conditions.
Note 2: Guaranteed by design and characterization.

OSCILLATOR

Maximum Duty Cycle

SYNC Input Signal Duty-Cycle

Range

Minimum SYNC Input Logic Low

Pulse Width

R

= 500kΩ ±1% 90 100 110

FREQ

R

= 147kΩ ±1% 255 300 345 Oscillator Frequency

FREQ

R

= 76.8kΩ ±1% 500

FREQ

R

= 500kΩ ±1% 93 96 97

FREQ

R

= 147kΩ ±1% 85 88 90

FREQ

R

= 76.8kz ±1% 80

FREQ

kHz

7 93 %

50 200 ns

%

SYNC Input Rise/Fall Time (Note 2) 200 ns
SYNC Input Frequency Range 100 550 kHz

DIGITAL INPUTS

POL, SYNC, SHDN Input High

Voltage

POL, SYNC, SHDN Input Low

Voltage

2.0 V

0.45 V

POL, SYNC Input Current POL, SYNC = GND or VL 20 40 µA

V

= +5V or GND -12 -4 0

SHDN Input Current

SHDN

V

= +16.5V 1.5 6

SHDN

µA

SOFT-START
Soft-Start Clock Cycles 1024

Cycles

Soft-Start Levels 64
EXT OUTPUT
EXT Sink/Source Current V

EXT On-Resistance

= +5V, V

IN

forced to +2.5V 1 A

EXT

EXT high or low, tested with 100mA load, V
EXT high or low, tested with 100mA load, V

= +5V 2 5

IN

= +3V 5 10

IN

Ω

MAX1846/MAX1847

High-Efficiency, Current-Mode,
Inverting PWM Controller

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

(V

SHDN

= VIN= +12V, SYNC = GND, PGND = GND, R

FREQ

= 147kΩ ±1%, CVL= 0.47µF, C

REF

= 0.1µF, TA= -40°C to +85°C,

unless otherwise noted.) (Note 3)

PARAMETER CONDITIONS MIN MAX UNITS

PWM CONTROLLER

Operating Input Voltage Range 3.0 16.5 V

V

rising 2.95

UVLO Threshold

IN

V

falling 2.6

IN

FB Threshold No load -20 20 mV
FB Input Current V

Load Regulation

= -0.1V -50 50 nA

FB

C

= 0.068µF, V

COMP

I

= 20mA to 200mA (Note 1)

OUT

OUT

= -48V,

-2 0 %

Current Limit Threshold 85 115 mV
CS Input Current CS = GND 20 µA
Supply Current V
Shutdown Supply Current SHDN = GND, V

= -0.1V, VIN = +3.0V to +16.5V 1.2 mA

FB

= +3.0V to +16.5V 25 µA

IN

REFERENCE AND VL REGULATOR
REF Output Voltage I
REF Load Regulation I
VL Output Voltage I
VL Load Regulation I

= 50µA 1.225 1.275 V

REF

= 0 to 500µA -15 mV

REF

= 100µA 3.85 4.65 V

VL

= 0.1mA to 2.0mA -60 mV

VL

OSCILLATOR

R

= 500kΩ ±1% 84 116

Oscillator Frequency

Maximum Duty Cycle

SYNC Input Signal Duty-Cycle

Range

Minimum SYNC Input Logic Low

Pulse Width

FREQ

R

= 147kΩ ±1% 255 345

FREQ

R

= 500kΩ ±1% 93 98

FREQ

R

= 147kΩ ±1% 84 93

FREQ

7 93 %

200 ns

SYNC Input Rise/Fall Time (Note 2) 200 ns
SYNC Input Frequency Range 100 550 kHz

DIGITAL INPUTS

POL, SYNC, SHDN Input High

Voltage

POL, SYNC, SHDN Input Low

Voltage

2.0 V

0.45 V

V

kHz

%

MAX1846/MAX1847

High-Efficiency, Current-Mode,

Inverting PWM Controller

_______________________________________________________________________________________ 5

Typical Operating Characteristics

(Circuit references are from Table 1 in the Main Application Circuits section, CVL= 0.47µF, C

RE

F

= 0.1µF, TA = +25°C, unless otherwise

noted.)

ELECTRICAL CHARACTERISTICS (continued)

(V

SHDN

= VIN= +12V, SYNC = GND, PGND = GND, R

FREQ

= 147kΩ ±1%, CVL= 0.47µF, C

REF

= 0.1µF, TA= -40°C to +85°C,

unless otherwise noted.) (Note 3)

Note 3: Parameters to -40°C are guaranteed by design and characterization.

PARAMETER CONDITIONS MIN MAX UNITS

POL, SYNC Input Current POL, SYNC = GND or VL 40 µA

V

= +5V or GND -12 0

SHDN Input Current

SHDN

V

= +16.5V 6

SHDN

EXT OUTPUT

EXT On-Resistance

EXT high or low, I
EXT high or low, I

= 100mA, VIN = +5V 7.5

EXT

= 100mA, VIN = +3V 12

EXT

EFFICIENCY vs. LOAD CURRENT

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

VIN = 5V

VIN = 16.5V

APPLICATION CIRCUIT A

1 10 100 1000 10,000

LOAD CURRENT (mA)

MAX1846/7 toc01

EFFICIENCY (%)

V

= -5V

OUT

EFFICIENCY vs. LOAD CURRENT

100

90

80

70

60

50

40

30

20

10

APPLICATION CIRCUIT B

0

1 10 100 1000 10,000

LOAD CURRENT (mA)

VIN = 3V

V

OUT

VIN = 5V

VIN = 3.3V

= -12V

EFFICIENCY vs. LOAD CURRENT

100

90

MAX1846/7 toc02

EFFICIENCY (%)

80

70

60

50

40

30

20

10

0

VIN = 12V

VIN = 16.5V

APPLICATION CIRCUIT C

1 100010010

LOAD CURRENT (mA)

V

= -48V

OUT

µA

Ω

MAX1846/7 toc03

OUTPUT VOLTAGE LOAD REGULATION

-11.90

-11.92

-11.94

-11.96

-11.98

-12.00

-12.02

OUTPUT VOLTAGE (V)

-12.04

-12.06

-12.08

APPLICATION CIRCUIT B VIN = 5V

-12.10

0 200100 300 400 500 600

LOAD CURRENT (mA)

MAX1846/7 toc04

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

0462 8 10 12 14 16

VIN (V)

(mA)

IN

I

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

VFB = -0.1V

MAX1846/7 toc05

REFERENCE VOLTAGE

vs. TEMPERATURE

1.262

1.258

1.254

(V)

1.250

REF

V

1.246

1.242

1.238

-40 20 40-20 0 60 80 100

TEMPERATURE (°C)

MAX1846/7 toc06

MAX1846/MAX1847

High-Efficiency, Current-Mode,
Inverting PWM Controller

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Circuit references are from Table 1 in the Main Application Circuits section, CVL= 0.47µF, C

RE

F

= 0.1µF, TA = +25°C, unless otherwise

noted.)

1.240

1.245

1.255

1.250

1.260

0 100 200 300 400 500

REFERENCE LOAD REGULATION

MAX1846/7 toc07

I

REF

(µA)

V

REF

(V)

4.100

4.180

4.140

4.260

4.220

4.300

4.340

-40 20 40-20 0 60 80 100

VL VOLTAGE

vs. TEMPERATURE

MAX1846/7 toc08

TEMPERATURE (°C)

VL (V)

I

VL

= 0

4.22

4.23

4.24

4.25

4.26

4.27

0 0.8 1.00.4 0.60.2 1.2 1.4 1.6 1.8 2.0

VL LOAD REGULATION

MAX1846/7 toc09

IVL (mA)

VL (V)

SHUTDOWN SUPPLY CURRENT

16

14

12

10

SHUTDOWN SUPPLY CURRENT (µA)

302

301

300

299

298

297

FREQUENCY (kHz)

296

295

294

VIN = 16.5V

8

6

4

2

0

-40 0 20-20

-40 0 20-20

SWITCHING FREQUENCY

vs. TEMPERATURE

VIN = 10V

VIN = 3V

40

TEMPERATURE (°C)

vs. TEMPERATURE

R

= 147kΩ ±1%

FREQ

40

TEMPERATURE (°C)

60 80 100

60 80 100

14

12

MAX1846/7 toc10

10

8

6

4

OPERATING CURRENT (mA)

2

0

-40 0 20-20 40 60 80 100

160

140

MAX1846/7 toc13

120

100

80

TIME (ns)

60

40

20

0

OPERATING CURRENT

vs. TEMPERATURE

A: VIN = 3V, V

APPLICATION CIRCUIT A
B: VIN = 5V, V
C: V

IN

= -12V

OUT

= -5V

OUT

= 16.5V, V

OUT

TEMPERATURE (°C)

= -5V

A

B

C

EXT RISE/FALL TIME

vs. CAPACITANCE

FALL TIME

RISE TIME

VIN = 12V

0 2000 4000 6000 8000 10,000

CAPACITANCE (pF)

MAX1846/7 toc11

MAX1846/7 toc14

SHDN

500

400

300

(kHz)

OSC

f

200

100

V

OUT

0

0

I

L

SWITCHING FREQUENCY

vs. R

FREQ

0 200100 300 400 500 600

R

(kΩ)

FREQ

EXITING SHUTDOWN

APPLICATION CIRCUIT B

1ms/div

MAX1846/7 toc12

MAX1846/7 toc15

5V/div

5V/div

1A/div