19-2286; Rev 1; 9/03
Low-Cost Voltage-Mode PWM
Step-Down Controllers
General Description
The MAX1966/MAX1967 are voltage-mode pulse-width-
modulated (PWM), step-down DC-DC controllers that
are ideal for a variety of cost-sensitive applications.
They drive low-cost N-MOSFETs for both the high-side
switch and synchronous rectifier and require no external
Schottky power diode or current-sense resistor. Short-
circuit and current-limit protection is provided by sens-
ing the drain-to-source voltage on the low-side FET.
Both devices can supply outputs as low as 0.8V and are
well suited for DSP cores and other low-voltage logic.
The MAX1966 has an input range of 2.7V to 5.5V while
the MAX1967 has an input range of 2.7V to 28V. In
ultra-low-cost designs, the MAX1966/MAX1967 can
provide efficiency exceeding 90% and can achieve
95% efficiency with optimized component selection.
The MAX1966/MAX1967 operate at 100kHz and ac-
commodate aluminum electrolytic capacitors and pow-
dered-iron core magnetics in minimum-cost designs.
They also provide excellent performance with high-per-
formance surface-mount components. The MAX1966 is
available in a low-cost 8-pin SO package. The MAX1967
is available in a 10-pin µMAX package.
o
Cost-Optimized Design
o
No Schottky Diode or Current-Sense Resistor
Required
o
>95% Efficiency
o
Low-Cost External Components
o
All N-Channel FET Design
o
2.7V to 5.5V Input Range (MAX1966)
o
2.7V to 28V Input Range (MAX1967)
o
0.8V Feedback for Low-Voltage Outputs
o
100kHz Switching Frequency Accommodates
Low-Cost Components
o
Thermal Shutdown
o
Output Current-Limit and Short-Circuit Protection
Features
MAX1966/MAX1967
Ordering Information
PART
MAX1966ESA
MAX1967EUB
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 SO
10 µMAX
Applications
Set-Top Boxes
Graphic Card Supplies
xDSL Modems and
Routers
Cable Modems and
Routers
Telecom Power Supplies
Networking Power
Supplies
Termination Supplies
Typical Operating Circuit
2.7V TO
5.5V INPUT
Pin Configurations
VIN
BST
DH
V
OUT
LX
COMP/EN
DL
TOP VIEW
MAX1966
BST
COMP/EN
FB
1
2
8
7
DH
LX
GND
DL
GND
MAX1966
3
6
5
VIN 4
FB
SO
Pin Configurations continued 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.
Low-Cost Voltage-Mode PWM
Step-Down Controllers
MAX1966/MAX1967
ABSOLUTE MAXIMUM RATINGS
(All Voltages Referenced to GND, Unless Otherwise Noted)
VIN to GND (MAX1966)............................................-0.3V to +6V
VIN to GND (MAX1967)..........................................-0.3V to +30V
VCC to GND (MAX1967)..........-0.3V, lower of 6V or (V
IN
+ 0.3V)
FB to GND ................................................................-0.3V to +6V
DL, COMP/EN to GND (MAX1966) ................-0.3V to V
IN
+ 0.3V
VL, DL, COMP/EN to GND (MAX1967).........-0.3V to V
CC
+ 0.3V
BST to LX..................................................................-0.3V to +6V
DH to LX........................................................-0.3V to BST + 0.3V
VL Short to GND (MAX1967) ....................................................5s
RMS Input Current (any pin).............................................±50mA
Continuous Power Dissipation (T
A
= +70°C)
8-Pin SO (derate 5.88mW/°C above +70°C)................471mW
10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW
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
(VIN = VL = VCC = 5V (MAX1967), VIN = 5V (MAX1966), T
A
= -40°C to +85°C (Note 1), unless otherwise noted. Typical values are at
T
A
= +25°C.)
PARAMETER
MAX1967 VIN Operating Range
MAX1967 Operating Range with
VIN = VL
MAX1966 VIN Operating Range
MAX1967 VL Undervoltage
Lockout (UVLO) Trip Level
MAX1966 VIN UVLO
Trip Level
Operating Supply Current
VL Output Voltage (MAX1967 Only)
Thermal Shutdown (Note 1)
OSCILLATOR
Frequency
Minimum Duty Cycle
Maximum Duty Cycle
SOFT-START
Digital Ramp Period
Soft-Start Levels
ERROR AMPLIFIER
FB Regulation Voltage
(MAX1967)
FB Regulation Voltage
(MAX1966)
FB to COMP/EN Gain
2.7V < VCC < 5.5V, 0°C to +85°C
2.7V < VCC < 5.5V, -40°C to +85°C
2.7V < VIN < 5.5V, 0°C to +85°C
2.7V < VIN < 5.5V, -40°C to +85°C
0.787
0.782
0.787
0.782
0.800
0.800
0.800
0.800
4000
0.815
0.815
0.815
0.815
V
V
V/V
Internal 6-bit DAC for converter to ramp from
0 to full output voltage
1024 /
f
OSC
V
OUT
/
64
s
V
90
95
f
OSC
0°C to +85°C
-40°C to +85°C
82
79
102
102
124
127
10
kHz
%
%
Rising and falling edge, hysteresis = 2%
Rising and falling edge, hysteresis = 2%
FB = 0.88V, no switching
5.5V < VIN < 28V, 1mA < I
VL
< 25mA,
FB = 0.88V
Rising temperature, typical hysteresis = 10°C
4.67
SYMBOL
CONDITIONS
MIN
4.9
2.7
2.7
2.35
2.35
2.53
2.53
0.7
5
160
TYP
MAX
28
5.5
5.5
2.66
2.66
3
5.3
UNITS
V
V
V
V
V
mA
V
°C
2
_______________________________________________________________________________________
Low-Cost Voltage-Mode PWM
Step-Down Controllers
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VL = VCC = 5V (MAX1967), VIN = 5V (MAX1966), T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at
T
A
= +25°C.)
PARAMETER
FB to COMP/EN
Transconductance
FB Input Bias Current
COMP/EN Source Current
Current-Limit Threshold Voltage
(Across Low-Side NFET)
MOSFET DRIVERS
Break-Before-Make Time
DH On-Resistance in Low State
DH On-Resistance in High State
DH Peak Source and Sink
Current
DL On-Resistance in Low State
DL On-Resistance in High State
DL Source Current
DL Sink Current
Maximum Total (DH + DL)
Average Source Current
BST Leakage Current
LX Leakage Current
V
BST
= 5V, V
LX
= 0, I
DH
= -50mA
V
BST
= 5V, V
LX
= 0, I
DH
= 50mA
V
BST
= 5V, V
LX
= 0, DH = 2.5V
I
DL
= -50mA
I
DL
= 50mA
V
DL
= 2.5V
V
DL
= 2.5V
V
BST
= 5V, V
LX
= 0
V
BST
= 33V, V
LX
= 28V
V
BST
= 33V, V
LX
= 28V
30
1.6
2.5
1
1.1
2.5
1
2
25
0
33
50
100
2.5
5.5
4
5.5
ns
Ω
Ω
A
Ω
Ω
A
A
mA
µA
µA
SYMBOL
CONDITIONS
-5µA < I
COMP/EN
< 5µA
V
FB
= 0.880V
V
COMP/EN
= 0
LX to GND
15
-340
MIN
70
TYP
108
3
46
-305
MAX
160
100
100
-270
UNITS
µS
nA
µA
mV
MAX1966/MAX1967
Note 1:
Specifications to -40°C are guaranteed by design and not production tested.
Note 2:
Thermal shutdown disables the buck regulator when the die reaches this temperature. Soft-start is reset and COMP/EN is
discharged to zero. In the MAX1967, the VL regulator remains on during thermal shutdown.
_______________________________________________________________________________________
3
Low-Cost Voltage-Mode PWM
Step-Down Controllers
MAX1966/MAX1967
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(1.2V/3A)
MAX1966 toc01
EFFICIENCY vs. LOAD CURRENT (1.8V/3A)
MAX1966
MAX1966 toc02
EFFICIENCY vs. LOAD CURRENT (1.2V/5A)
MAX1966
V
IN
= 5.0V
90
EFFICIENCY (%)
V
IN
= 3.3V
MAX1966 toc03
100
V
IN
= 3.3V
100
V
IN
= 3.3V
90
EFFICIENCY (%)
100
90
EFFICIENCY (%)
80
V
IN
= 5.0V
70
80
V
IN
= 5.0V
70
80
V
IN
= 3.3V
70
V
IN
= 5.0V
60
MAX1966
FIGURE 1
50
0.01
0.1
1
10
LOAD CURRENT (A)
60
MAX1966
FIGURE 1
50
0.01
0.1
1
10
LOAD CURRENT (A)
60
MAX1966
FIGURE 1
50
0.01
0.1
1
10
LOAD CURRENT (A)
EFFICIENCY vs. LOAD CURRENT (1.8V/5A)
MAX1966
MAX1966 toc04
EFFICIENCY vs. LOAD CURRENT (1.2V/3A)
MAX1967
MAX1966 toc05
EFFICIENCY vs. LOAD CURRENT (1.8V/3A)
MAX1967
MAX1966 toc06
100
100
100
90
V
IN
= 3.3V
EFFICIENCY (%)
EFFICIENCY (%)
80
V
IN
= 5.0V
70
90
EFFICIENCY (%)
V
IN
= 5V
80
V
IN
= 12V
90
V
IN
= 5V
80
V
IN
= 12V
70
70
60
MAX1966
FIGURE 1
0.01
0.1
1
10
60
MAX1967
FIGURE 2
0.01
0.1
1
10
LOAD CURRENT (A)
60
MAX1967
FIGURE 2
50
0.01
0.1
1
10
LOAD CURRENT (A)
50
LOAD CURRENT (A)
50
EFFICIENCY vs. LOAD CURRENT (3.3V/3A)
MAX1967
MAX1966 toc07
EFFICIENCY vs. LOAD CURRENT (1.2V/5A)
MAX1967
MAX1966 toc08
EFFICIENCY vs. LOAD CURRENT (1.8V/5A)
MAX1967
MAX1966 toc09
100
100
V
IN
= 5V
90
EFFICIENCY (%)
V
IN
= 5V
100
V
IN
= 5V
90
EFFICIENCY (%)
V
IN
= 5V
90
EFFICIENCY (%)
80
V
IN
= 12V
70
80
80
V
IN
= 12V
70
V
IN
= 12V
V
IN
= 20V
MAX1967
FIGURE 2
0.01
0.1
1
10
LOAD CURRENT (A)
70
V
IN
= 20V
60
MAX1967
FIGURE 2
0.01
0.1
1
10
LOAD CURRENT (A)
60
60
MAX1967
FIGURE 2
0.01
0.1
1
10
LOAD CURRENT (A)
50
50
50
4
_______________________________________________________________________________________
Low-Cost Voltage-Mode PWM
Step-Down Controllers
Typical Operating Characteristics (continued)
(T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT (3.3V/5A)
MAX1967
MAX1966 toc10
MAX1966/MAX1967
FREQUENCY vs. INPUT VOLTAGE
MAX1966 toc11
FREQUENCY vs. TEMPERATURE
MAX1966 toc12
100
V
IN
= 5V
V
IN
= 12V
104
MAX1966
V
OUT
= 1.8V
FREQUENCY (kHz)
102
130
90
EFFICIENCY (%)
120
FREQUENCY (kHz)
80
110
70
V
IN
= 24V
100
MAX1967
V
OUT
= 3.3V
100
60
MAX1967
FIGURE 2
0.01
0.1
1
10
LOAD CURRENT (A)
90
98
2.5
7.0
11.5
16.0
20.5
25.0
INPUT VOLTAGE (V)
50
80
-40
-25 -10
5
20
35
50
65
80
TEMPERATURE (°C)
MAX1966 SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1966 toc13
MAX1967 SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1966 toc14
10
10
8
SUPPLY CURRENT (mA)
8
SUPPLY CURRENT (mA)
6
6
4
4
2
MAX1966
V
OUT
= 1.8V
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
2
MAX1967
V
OUT
= 3.3V
0
4
9
14
19
24
INPUT VOLTAGE (V)
LOAD STEP RESPONSE
MAX1966 toc15
START-UP WAVEFORM
MAX1966 toc16
V
IN
= 5.0V, V
OUT
= 1.8V
L = 22µH
I
LOAD
= 0.1 TO 3A
V
OUT
200mV/div
V
IN
2V/div
V
OUT
I
OUT
2A/div
INDUCTOR
CURRENT
2A/div
NO LOAD
400ms/div
2ms/div
1V/div
1A/div
INDUCTOR
CURRENT
_______________________________________________________________________________________
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