19-3105; Rev 2; 8/96
UAL
IT MAN
TION K
A
SHEET
EVALU
S DATA
W
FOLLO
Switch-Mode Regulator with
+5V to ±12V or ±15V Dual Output
____________________________Features
o
Specs Guaranteed for In-Circuit Performance
o
Load Currents to ±2A
o
4.2V to 10V Input-Voltage Range
o
Switches From ±15V to ±12V Under Logic Control
o
±4% Output Tolerance Max Over Temp, Line,
and Load
o
90% Typ Efficiency
o
o
o
o
Low-Noise, Current-Mode Feedback
Cycle-by-Cycle Current Limiting
Undervoltage Lockout and Soft-Start
100kHz or 200kHz Operation
_______________General Description
The MAX742 DC-DC converter is a controller for dual-out-
put 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 current-
mode feedback loops provide tight regulation and opera-
tion 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 shut-
down, 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.
MAX742
______________Ordering Information
PART
MAX742CPP
MAX742CWP
MAX742C/D
MAX742EPP
MAX742EWP
MAX742MJP
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
20 Plastic DIP
20 Wide SO
Dice*
20 Plastic DIP
20 Wide SO
20 CERDIP
________________________Applications
DC-DC Converter Module Replacement
Distributed Power Systems
Computer Peripherals
* Contact factory for dice specifications
__________Simplified Block Diagram
MAX742
CC-
+5V
INPUT
__________________Pin Configuration
TOP VIEW
FB+ 1
CC+ 2
AGND 3
AV 4
100/200 5
12/15 6
VREF 7
SS 8
CC- 9
FB- 10
20 CSH+
19 CSL+
18 GND
17 EXT+
R -SENSE
PWM
S -DRIVE
P
-VO
MAX742
16 PUMP
15 PDRV
14 EXT-
13 V+
12 CSH-
11 CSL-
+2.0V
VREF
OSC
+VO
S +DRIVE
PWM
R +SENSE
N
CC+
DIP/SO
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
Switch-Mode Regulator with
+5V to ±12V or ±15V Dual Output
MAX742
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, 12/15) ..................................-0.3V to (V+ + 0.3V)
Output Voltage to GND
(EXT+, PUMP) ..........................................-0.3V to (V+ + 0.3V)
EXT- to PDRV................................................-0.3V to (V+ + 0.3V)
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
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.
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 2, +4.5V < V+ < +5.5V.)
PARAMETER
Output Voltage, ±15V Mode
(Notes 1, 2)
Output Voltage, ±12V Mode
(Notes 1, 2)
SYMBOL
CONDITIONS
0mA < I
L
< 100mA,
12/15 = 0V
0mA < I
L
< 125mA,
12/15 = V+
T
A
= +25°C
T
A
= T
MIN
to T
MAX
T
A
= +25°C
T
A
= T
MIN
to T
MAX
MIN
14.55
14.40
11.64
11.52
TYP
MAX
15.45
15.60
12.36
12.48
UNITS
V
V
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 2, V+ = 5V, 100/200 = 12/15 = 0V; T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
Line Regulation
Load Regulation (Note 2)
No-Load Supply Current
Undervoltage Lockout
Undervoltage Lockout Hysteresis
Reference Output Voltage
Oscillator Frequency
PUMP Frequency
Duty-Cycle Limit (Note 3)
Positive Current-Limit Threshold
(CSH+ to CSL+)
Negative Current-Limit Threshold
(CSH- to CSL-)
EXT+ or EXT-
CSL+ = 0V, FB+ = open circuit
CSH- = V+, FB- = open circuit
85
150
150
f
OSC
100/200 = 0V
100/200 = V+
170
75
UVLO
SYMBOL
CONDITIONS
V+ = 4.5V to 5.5V, PDRV from PUMP
I
LOAD
= 0mA to 100mA
V+ = 5V
No EXT- or PUMP load,
FB+ = FB- = open circuit V+ = 10V
3.8
0.2
2.0
200
100
f
OSC
/2
90
225
225
300
300
230
125
MIN
TYP
0.01
30
MAX
0.05
100
3
10
4.2
UNITS
%/%
mV
mA
V
V
V
kHz
kHz
%
mV
mV
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; T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
Output Voltage High
Output Voltage Low
Output Sink Current
Output Source Current
Output Rise/Fall Time
PUMP Output Voltage (Note 4)
Compensation Pin Impedance
Thermal-Shutdown Threshold
Soft-Start Source Current
Soft-Start Sink Current
SS = 0V
V+ = 3.8V, SS = 2V
3
-2
SYMBOL
V
OH
V
OL
CONDITIONS
EXT+, EXT-, I
L
= 1mA, V+ = 4.5V, PDRV= -3V
EXT+, EXT-, I
L
= -1mA, V+ = 4.5V, PDRV= -3V
V+ = 4.5V, PDRV = -3V, EXT+ = 4.5V
T
A
= +25°C
EXT- = 4.5V
V+ = 4.5V, PDRV = -3V, EXT+ = 0V
T
A
= +25°C
EXT- = -3V
EXT+, C
LOAD
= 2nF
EXT-, C
LOAD
= 4nF, PDRV = -3V
V+ = 4.5V, I
L
= -5mA, T
A
= +25°C
CC+, CC-
10
190
7
-0.5
100
200
200
350
-200
-350
70
100
-3
-100
-200
MIN
4.3
-2.8
TYP
MAX
UNITS
V
V
mA
mA
ns
V
kΩ
°C
µA
mA
MAX742
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.
_______________________________________________________________________________________
3
Switch-Mode Regulator with
+5V to ±12V or ±15V Dual Output
MAX742
__________________________________________Typical Operating Characteristics
(Circuit of Figure 2, V+ = 5V, T
A
= +25°C, unless otherwise noted.)
UNDERVOLTAGE LOCKOUT HYSTERESIS
MAX742 -1
CHARGE-PUMP LOAD REGULATION
MAX742 -2
PDRV CURRENT vs. C
EXT-
PDRV FORCED TO -4V
PUMP DISCONNECTED
MAX742 -3
25
QUIESCENT SUPPLY CURRENT (mA)
±15V MODE,
200kHz MODE
20
-5.0
CHARGE-PUMP OUTPUT VOLTAGE (V)
MEASURED AT POINT A
-4.5
6
5
PDRV CURRENT (mA)
4
15
-4.0
V+ = 5V
200kHz
3
2
1
100kHz
10
LOCKOUT
ENABLED
-3.5
5
-3.0
V+ = 4.5V
-2.5
0
1
2
3
4
5
6
0
1
2
3 4
5
6 7
8
9
10
0
1
2
3
4
SUPPLY VOLTAGE (V)
CHARGE-PUMP LOAD CURRENT (mA)
CAPACITANCE AT EXT- (nF)
EFFICIENCY vs. LOAD CURRENT,
22W CIRCUIT, ±15V MODE
MAX742 -4
EFFICIENCY vs. LOAD CURRENT,
6W CIRCUIT, ±15V MODE
MAX742 -5
EFFICIENCY vs. LOAD CURRENT,
6W CIRCUIT, ±12V MODE
MAX742 -6
90
EFFICIENCY (%)
EFFICIENCY (%)
100kHz
80
200kHz
70
CIRCUIT OF FIGURE 3,
INDUCTORS = GOWANDA 121-AT2502
(MPP CORE),
Q2 = TWO IRF9Z30 IN PARALLEL
±15V MODE
0
±200
±400 ±600
±800 ±1000
90
100kHz
EFFICIENCY (%)
90
200kHz
100kHz
80
200kHz
80
70
70
60
60
INDUCTORS = GOWANDA 050-AT1003
(MPP CORE)
50
0
±50
±100
±150
±200
±250
60
INDUCTORS = GOWANDA 050-AT1003
(MPP CORE)
50
0
±75
±150
±225
±300
LOAD CURRENT (mA)
LOAD CURRENT (mA)
50
LOAD CURRENT (mA)
PEAK INDUCTOR CURRENT vs.
LOAD CURRENT
MAX742 -7
CURRENT-LIMIT THRESHOLD vs.
SOFT-START VOLTAGE
CURRENT-LIMIT THRESHOLD (mV)
MAX742 -8
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
PEAK INDUCTOR CURRENT (mA)
100kHz
200
200kHz
150
100
MEASURED AT LX-,
±15V MODE
50
100
150
200
50
0
1
2
3
LOAD CURRENT (mA)
SOFT-START VOLTAGE (V)
4
_______________________________________________________________________________________
Switch-Mode Regulator with
+5V to ±12V or ±15V Dual Output
_____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2, I
LOAD
= 100mA, unless otherwise noted.)
SWITCHING WAVEFORMS,
INVERTING SECTION
SWITCHING WAVEFORMS,
STEP-UP SECTION
MAX742
A
A
B
B
C
2µs/div
A = GATE DRIVE, 5V/div
B = SWITCH VOLTAGE, 10V/div
C = SWITCH CURRENT, 0.2A/div
2µs/div
A = GATE DRIVE, 5V/div
B = SWITCH VOLTAGE, 10V/div
C = SWITCH CURRENT, 0.2A/div
C
OUTPUT-VOLTAGE NOISE,
FILTERED AND UNFILTERED
LOAD-TRANSIENT RESPONSE
A
A
B
B
2µs/div
A = NOISE WITH i FILTER, 1mV/div
B = NOISE WITHOUT FILTER, 20mV/div
MEASURED AT -V
OUT
V+ = 5V
BW = 5MHz
200µs/div
A = +VO, 20mV/div
B = -VO, 50mV/div
_______________________________________________________________________________________
5
京公网安备 11010802033920号
EEWORLD
