19-2091; Rev 0; 8/01
High-Efficiency, Current-Mode,
Inverting PWM Controller
General Description
MAX1846/MAX1847 high-efficiency PWM inverting con-
trollers allow designers to implement compact, low-
noise, 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 fea-
ture 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, compati-
bility 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 shut-
down functions. The MAX1847 can also be configured
to operate as an inverting flyback controller with an N-
channel 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 pro-
vides good transient response. Accurate current-mode
control and over current protection are achieved
through low-side current sensing.
o
90% Efficiency
o
+3.0V to +16.5V Input Range
o
-2V to -200V Output
o
Drives High-Side P-Channel MOSFET
o
100kHz to 500kHz Switching Frequency
o
Current-Mode, PWM Control
o
Internal Soft-Start
o
Electrolytic or Ceramic Output Capacitor
o
The MAX1847 also offers:
Synchronization to External Clock
Shutdown
N-Channel Inverting Flyback Option
Features
MAX1846/MAX1847
Ordering Information
PART
MAX1846EUB
MAX1847EEE
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
10 µMAX
16 QSOP
Typical Operating Circuit
POSITIVE
V
IN
Applications
Cellular Base Stations
Networking Equipment
Optical Networking Equipment
SLIC Supplies
CO DSL Line Driver Supplies
Industrial Power Supplies
Automotive Electronic Power Supplies
Servers
FREQ
PGND
VL
IN
EXT
P
NEGATIVE
V
OUT
MAX1846
MAX1847
COMP
CS
REF
GND
FB
Pin Configurations appear at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
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.
High-Efficiency, Current-Mode,
Inverting PWM Controller
MAX1846/MAX1847
ABSOLUTE MAXIMUM RATINGS
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 (V
IN
+ 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
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
(V
SHDN
= V
IN
= +12V, SYNC = GND, PGND = GND, R
FREQ
= 147kΩ ±1%, C
VL
= 0.47µF, C
REF
= 0.1µF,
T
A
= 0°C to +85°C,
unless
otherwise noted.)
PARAMETER
PWM CONTROLLER
Operating Input Voltage Range
UVLO Threshold
UVLO Hysteresis
FB Threshold
FB Input Current
Load Regulation
Line Regulation
Current-Limit Threshold
CS Input Current
Supply Current
Shutdown Supply Current
REF Output Voltage
REF Load Regulation
VL Output Voltage
VL Load Regulation
CS = GND
V
FB
= -0.1V, V
IN
= +3.0V to +16.5V
SHDN
= GND, V
IN
= +3.0V to +16.5V
I
REF
= 50µA
I
REF
= 0 to 500µA
I
VL
= 100µA
I
VL
= 0.1mA to 2.0mA
3.85
1.236
No load
V
FB
= -0.1V
C
COMP
= 0.068µF, V
OUT
= -48V,
I
OUT
= 20mA to 200mA (Note 1)
C
COMP
= 0.068µF, V
OUT
= -48V,
V
IN
= +8V to +16.5V, I
OUT
= 100mA
85
-12
-50
-1
0.04
100
10
0.75
10
1.25
-2
4.25
-20
115
20
1.2
25
1.264
-15
4.65
-60
V
IN
rising
V
IN
falling
2.6
3.0
2.8
2.74
60
0
-6
12
50
0
16.5
2.95
V
V
mV
mV
nA
%
%
mV
µA
mA
µA
V
mV
V
mV
CONDITIONS
MIN
TYP
MAX
UNITS
REFERENCE AND VL REGULATOR
2
_______________________________________________________________________________________
High-Efficiency, Current-Mode,
Inverting PWM Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
SHDN
= V
IN
= +12V, SYNC = GND, PGND = GND, R
FREQ
= 147kΩ ±1%, C
VL
= 0.47µF, C
REF
= 0.1µF,
T
A
= 0°C to +85°C,
unless
otherwise noted.)
OSCILLATOR
R
FREQ
= 500kΩ
±1%
Oscillator Frequency
R
FREQ
= 147kΩ
±1%
R
FREQ
= 76.8kΩ
±1%
R
FREQ
= 500kΩ
±1%
Maximum Duty Cycle
SYNC Input Signal Duty-Cycle
Range
Minimum SYNC Input Logic Low
Pulse Width
SYNC Input Rise/Fall Time
SYNC Input Frequency Range
DIGITAL INPUTS
POL, SYNC,
SHDN
Input High
Voltage
POL, SYNC,
SHDN
Input Low
Voltage
POL, SYNC Input Current
SHDN
Input Current
SOFT-START
Soft-Start Clock Cycles
Soft-Start Levels
EXT OUTPUT
EXT Sink/Source Current
EXT On-Resistance
V
IN
= +5V, V
EXT
forced to +2.5V
EXT high or low, tested with 100mA load, V
IN
= +5V
EXT high or low, tested with 100mA load, V
IN
= +3V
1
2
5
5
10
A
Ω
1024
64
Cycles
POL, SYNC = GND or VL
V
SHDN
= +5V or GND
V
SHDN
= +16.5V
-12
20
-4
1.5
2.0
0.45
40
0
6
V
V
µA
µA
(Note 2)
100
R
FREQ
= 147kΩ
±1%
R
FREQ
= 76.8kz
±1%
7
50
93
85
90
255
100
300
500
96
88
80
93
200
200
550
%
ns
ns
kHz
97
90
%
110
345
kHz
MAX1846/MAX1847
Note 1:
Production test correlates to operating conditions.
Note 2:
Guaranteed by design and characterization.
_______________________________________________________________________________________
3
High-Efficiency, Current-Mode,
Inverting PWM Controller
MAX1846/MAX1847
ELECTRICAL CHARACTERISTICS
(V
SHDN
= V
IN
= +12V, SYNC = GND, PGND = GND, R
FREQ
= 147kΩ ±1%, C
VL
= 0.47µF, C
REF
= 0.1µF,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 3)
PARAMETER
PWM CONTROLLER
Operating Input Voltage Range
UVLO Threshold
FB Threshold
FB Input Current
Load Regulation
Current Limit Threshold
CS Input Current
Supply Current
Shutdown Supply Current
REF Output Voltage
REF Load Regulation
VL Output Voltage
VL Load Regulation
OSCILLATOR
Oscillator Frequency
Maximum Duty Cycle
SYNC Input Signal Duty-Cycle
Range
Minimum SYNC Input Logic Low
Pulse Width
SYNC Input Rise/Fall Time
SYNC Input Frequency Range
DIGITAL INPUTS
POL, SYNC,
SHDN
Input High
Voltage
POL, SYNC,
SHDN
Input Low
Voltage
2.0
0.45
V
V
(Note 2)
100
R
FREQ
= 500kΩ
±1%
R
FREQ
= 147kΩ
±1%
R
FREQ
= 500kΩ
±1%
R
FREQ
= 147kΩ
±1%
84
255
93
84
7
116
345
98
93
93
200
200
550
kHz
%
%
ns
ns
kHz
CS = GND
V
FB
= -0.1V, V
IN
= +3.0V to +16.5V
SHDN
= GND, V
IN
= +3.0V to +16.5V
I
REF
= 50µA
I
REF
= 0 to 500µA
I
VL
= 100µA
I
VL
= 0.1mA to 2.0mA
3.85
1.225
V
IN
rising
V
IN
falling
No load
V
FB
= -0.1V
C
COMP
= 0.068µF, V
OUT
= -48V,
I
OUT
= 20mA to 200mA (Note 1)
2.6
-20
-50
-2
85
20
50
0
115
20
1.2
25
1.275
-15
4.65
-60
3.0
16.5
2.95
V
V
mV
nA
%
mV
µA
mA
µA
V
mV
V
mV
CONDITIONS
MIN
MAX
UNITS
REFERENCE AND VL REGULATOR
4
_______________________________________________________________________________________
High-Efficiency, Current-Mode,
Inverting PWM Controller
MAX1846/MAX1847
ELECTRICAL CHARACTERISTICS (continued)
(V
SHDN
= V
IN
= +12V, SYNC = GND, PGND = GND, R
FREQ
= 147kΩ ±1%, C
VL
= 0.47µF, C
REF
= 0.1µF,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 3)
PARAMETER
POL, SYNC Input Current
SHDN
Input Current
EXT OUTPUT
EXT On-Resistance
EXT high or low, I
EXT
= 100mA, V
IN
= +5V
EXT high or low, I
EXT
= 100mA, V
IN
= +3V
7.5
12
Ω
CONDITIONS
POL, SYNC = GND or VL
V
SHDN
= +5V or GND
V
SHDN
= +16.5V
-12
MIN
MAX
40
0
6
UNITS
µA
µA
Note 3:
Parameters to -40°C are guaranteed by design and characterization.
Typical Operating Characteristics
(Circuit references are from Table 1 in the
Main Application Circuits
section, C
VL
= 0.47µF, C
REF
= 0.1µF, T
A
= +25°C, unless otherwise
noted.)
EFFICIENCY vs. LOAD CURRENT
MAX1846/7 toc01
EFFICIENCY vs. LOAD CURRENT
V
IN
= 5V
MAX1846/7 toc02
EFFICIENCY vs. LOAD CURRENT
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
V
IN
= 16.5V
V
IN
= 12V
MAX1846/7 toc03
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
1
APPLICATION CIRCUIT A
10
100
V
OUT
= -5V
1000
V
IN
= 16.5V
V
IN
= 5V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
APPLICATION CIRCUIT B
1
10
100
V
IN
= 3V
100
V
IN
= 3.3V
V
OUT
= -12V
1000
10,000
0
1
APPLICATION CIRCUIT C
10
100
V
OUT
= -48V
1000
10,000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
OUTPUT VOLTAGE LOAD REGULATION
MAX1846/7 toc04
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
1.4
1.2
1.0
I
IN
(mA)
0.8
0.6
0.4
0.2
1.242
V
FB
= -0.1V
0
1.238
16
-40
-20
MAX1846/7 toc05
REFERENCE VOLTAGE
vs. TEMPERATURE
MAX1846/7 toc06
-11.90
-11.92
-11.94
OUTPUT VOLTAGE (V)
-11.96
-11.98
-12.00
-12.02
-12.04
-12.06
-12.08
-12.10
0
APPLICATION CIRCUIT B
100
200
300
V
IN
= 5V
400
500
1.6
1.262
1.258
1.254
V
REF
(V)
1.250
1.246
600
0
2
4
6
8
V
IN
(V)
10
12
14
0
20
40
60
80
100
LOAD CURRENT (mA)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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