Rainbow Electronics MAX742 User Manual

19-3105; Rev 2; 8/96

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

Switch-Mode Regulator with

+5V to ±12V or ±15V Dual Output

_______________General Description

The MAX742 DC-DC converter is a controller for dual-out­put power supplies in the 3W to 60W range. Relying on
simple two-terminal inductors rather than transformers, the
MAX742 regulates both outputs independently to within
±4% over all conditions of line voltage, temperature, and
load current.

The MAX742 has high efficiency (up to 92%) over a wide
range of output loading. Two independent PWM current­mode feedback loops provide tight regulation and opera­tion free from subharmonic noise. The MAX742 can
operate at 100kHz or 200kHz, so it can be used with small
and lightweight external components. Also ripple and
noise are easy to filter. The MAX742 provides a regulated
output for inputs ranging from 4.2V to 10V (and higher with
additional components).

External power MOSFETs driven directly from the MAX742
are protected by cycle-by-cycle overcurrent sensing. The
MAX742 also features undervoltage lockout, thermal shut­down, and programmable soft-start.

If 3W of load power or less is needed, refer to the MAX743
data sheet for a device with internal power MOSFETs.

________________________Applications

DC-DC Converter Module Replacement
Distributed Power Systems
Computer Peripherals

__________________Pin Configuration

____________________________Features

♦ Specs Guaranteed for In-Circuit Performance
♦ Load Currents to ±2A
♦ 4.2V to 10V Input-Voltage Range
♦ Switches From ±15V to ±12V Under Logic Control
♦ ±4% Output Tolerance Max Over Temp, Line,

and Load

♦ 90% Typ Efficiency
♦ Low-Noise, Current-Mode Feedback
♦ Cycle-by-Cycle Current Limiting
♦ Undervoltage Lockout and Soft-Start
♦ 100kHz or 200kHz Operation

______________Ordering Information

PART

MAX742CPP

MAX742CWP
MAX742C/D 0°C to +70°C
MAX742EPP -40°C to +85°C 20 Plastic DIP
MAX742EWP
MAX742MJP -55°C to +125°C

* Contact factory for dice specifications

TEMP. RANGE PIN-PACKAGE

0°C to +70°C
0°C to +70°C

-40°C to +85°C 20 Wide SO

20 Plastic DIP
20 Wide SO
Dice*

20 CERDIP

__________Simplified Block Diagram

+5V

MAX742

CC-

INPUT

MAX742

TOP VIEW

R

FB+

1

CC+

2

AGND

3

AV

4

100/200

12/15

VREF

SS

CC-

FB-

________________________________________________________________

MAX742

5
6
7
8
9

10

DIP/SO

CSH+

20

CSL+

19

GND

18

EXT+

17

PUMP

16

PDRV

15

EXT-

14

V+

13

CSH-

12

CSL-

11

+2.0V
VREF

CC+

-SENSE

PWM

S

-DRIVE

OSC

+DRIVE

S

PWM
+SENSE

R

Maxim Integrated Products

P

N

-VO

+VO

1

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

Switch-Mode Regulator with
+5V to ±12V or ±15V Dual Output

ABSOLUTE MAXIMUM RATINGS

V+, AV+ to AGND, GND.........................................-0.3V to +12V

PDRV to V+.............................................................+0.3V to -14V

FB+, FB- to GND..................................................................±25V

Input Voltage to GND

(CC+, CC-, CSH+, CSL+, CSH-, CSL-,
SS, 100/200

Output Voltage to GND

MAX742

(EXT+, PUMP) ..........................................-0.3V to (V+ + 0.3V)

EXT- to PDRV................................................-0.3V to (V+ + 0.3V)

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.

, 12/15)..................................-0.3V to (V+ + 0.3V)

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 2, +4.5V < V+ < +5.5V.)

Continuous Power Dissipation (any package)

up to +70°C.....................................................................500mW

derate above +70°C by ..........................................100mW/°C

Operating Temperature Ranges

MAX742C_ _ .......................................................0°C to +70°C

MAX742E_ _ ....................................................-40°C to +85°C

MAX742MJP ..................................................-55°C to +125°C

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

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

Output Voltage, ±15V Mode
(Notes 1, 2)

Output Voltage, ±12V Mode
(Notes 1, 2)

0mA < IL< 100mA,
12/15 = 0V

0mA < IL< 125mA,
12/15 = V+

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 2, V+ = 5V, 100/200 = 12/15 = 0V; TA= T

V+ = 4.5V to 5.5V, PDRV from PUMP
I

Load Regulation (Note 2)
No-Load Supply Current

Oscillator Frequency

Positive Current-Limit Threshold
(CSH+ to CSL+)

Negative Current-Limit Threshold
(CSH- to CSL-)

f

OSC

= 0mA to 100mA

LOAD

No EXT- or PUMP load,
FB+ = FB- = open circuit

100/200 = 0V
100/200 = V+

EXT+ or EXT­CSL+ = 0V, FB+ = open circuit

CSH- = V+, FB- = open circuit

CONDITIONS

to T

MIN

CONDITIONS

TA= +25°C
TA= T
TA= +25°C
TA= T

, unless otherwise noted.)

MAX

V+ = 5V

MIN

MIN

to T

to T

MAX

MAX

14.55 15.45

14.40 15.60

11.64 12.36

11.52 12.48

3

10V+ = 10V

170 200 230

75 100 125

/2PUMP Frequency

OSC

UNITSMIN TYP MAXSYMBOLPARAMETER

V

V

UNITSMIN TYP MAXSYMBOLPARAMETER

%/%0.01 0.05Line Regulation

mV30 100
mA

V3.8 4.2UVLOUndervoltage Lockout
V0.2Undervoltage Lockout Hysteresis

V2.0Reference Output Voltage
kHz
kHzf

%85 90Duty-Cycle Limit (Note 3)

mV150 225 300

mV150 225 300

2 _______________________________________________________________________________________

Switch-Mode Regulator with

+5V to ±12V or ±15V Dual Output

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 2, V+ = 5V, 100/200 = 12/15 = 0V; TA= T

Output Voltage High
Output Voltage Low

Output Sink Current

Output Source Current

Output Rise/Fall Time

Note 1: Devices are 100% tested to these limits under 0mA to 100mA and to 125mA conditions using automatic test equipment.

The ability to drive loads up to 1A is guaranteed by the current-limit threshold, output swing, and the output current
source/sink tests. See Figures 2 and 3.

Note 2: Actual load capability of the circuit of Figure 2 is ±200mA in ±15V mode and ±250mA in ±12V mode. Load regulation is

tested at lower limits due to test equipment limitations.

Note 3: Guaranteed by design.
Note 4: Measured at Point A, circuit of Figure 2, with PDRV disconnected.

EXT+, EXT-, IL= 1mA, V+ = 4.5V, PDRV= -3V

OH

EXT+, EXT-, IL= -1mA, V+ = 4.5V, PDRV= -3V

OL

V+ = 4.5V, PDRV = -3V,
TA= +25°C

V+ = 4.5V, PDRV = -3V,
TA= +25°C

EXT+, C

LOAD

V+ = 4.5V, IL= -5mA, TA= +25°C
CC+, CC-

SS = 0V
V+ = 3.8V, SS = 2V

to T

MIN

MAX

CONDITIONS

= 2nF

LOAD

= 4nF, PDRV = -3V

, unless otherwise noted.)

EXT+ = 4.5V
EXT- = 4.5V
EXT+ = 0V
EXT- = -3V

100 200
200 350

-200 -100

-350 -200
70

100EXT-, C

MAX742

UNITSMIN TYP MAXSYMBOLPARAMETER

V4.3V
V-2.8V

mA

mA

ns

V-3PUMP Output Voltage (Note 4)
kΩ10Compensation Pin Impedance
°C190Thermal-Shutdown Threshold
µA37Soft-Start Source Current

mA-2 -0.5Soft-Start Sink Current

_______________________________________________________________________________________ 3

Switch-Mode Regulator with
+5V to ±12V or ±15V Dual Output

__________________________________________Typical Operating Characteristics

(Circuit of Figure 2, V+ = 5V, TA = +25°C, unless otherwise noted.)

UNDERVOLTAGE LOCKOUT HYSTERESIS

25

±15V MODE,

MAX742

QUIESCENT SUPPLY CURRENT (mA)

200kHz MODE

20

15

10

5



06

EFFICIENCY vs. LOAD CURRENT,

22W CIRCUIT, ±15V MODE

90

80

70

EFFICIENCY (%)

CIRCUIT OF FIGURE 3,
INDUCTORS = GOWANDA 121-AT2502
(MPP CORE),

60

Q2 = TWO IRF9Z30 IN PARALLEL
±15V MODE

50



0



LOCKOUT
ENABLED

23 51

SUPPLY VOLTAGE (V)

±400 ±600 ±1000±200

LOAD CURRENT (mA)

4

200kHz

±800

100kHz

CHARGE-PUMP LOAD REGULATION

-5.0

MAX742 -1

-4.5

-4.0

-3.5

-3.0

CHARGE-PUMP OUTPUT VOLTAGE (V)

-2.5

MEASURED AT POINT A



0

23 75 6 10 891

4

CHARGE-PUMP LOAD CURRENT (mA)

EFFICIENCY vs. LOAD CURRENT,

6W CIRCUIT, ±15V MODE

MAX742 -4

90

80

70

EFFICIENCY (%)

60

INDUCTORS = GOWANDA 050-AT1003
(MPP CORE)

50



0

±100 ±150 ±250±50

LOAD CURRENT (mA)



V+ = 4.5V

V+ = 5V

200kHz

±200

100kHz

6

MAX742 -2

5

4

3

2

PDRV CURRENT (mA)

1



MAX742 -5

90

80

70

EFFICIENCY (%)

60

50



PDRV CURRENT vs. C



PDRV FORCED TO -4V
PUMP DISCONNECTED

200kHz

100kHz

0

CAPACITANCE AT EXT- (nF)

231

EFFICIENCY vs. LOAD CURRENT,

6W CIRCUIT, ±12V MODE

200kHz

INDUCTORS = GOWANDA 050-AT1003
(MPP CORE)

0

±150 ±225±75

LOAD CURRENT (mA)

EXT-

MAX742 -3

4

MAX742 -6

100kHz

±300

PEAK INDUCTOR CURRENT vs.

LOAD CURRENT


1200
1100
1000

900
800
700
600
500
400
300

PEAK INDUCTOR CURRENT (mA)

200
100





0

MEASURED AT LX-,
±15V MODE

100 15050

LOAD CURRENT (mA)

100kHz

MAX742 -7

200

200kHz

150

100

CURRENT-LIMIT THRESHOLD (mV)

200

CURRENT-LIMIT THRESHOLD vs.

SOFT-START VOLTAGE

50





0

12

SOFT-START VOLTAGE (V)

4 _______________________________________________________________________________________

MAX742 -8

3