19-2198; Rev 0; 10/01
KIT
EVALUATION
LE
AVAILAB
3A, 1MHz, Low-Voltage, Step-Down Regulators with
Synchronous Rectification and Internal Switches
General Description
The MAX1830/MAX1831 constant-off-time, pulse-width-
modulated (PWM) step-down DC-DC converters are
ideal for use in 5V and 3.3V to low-voltage conversion
necessary in notebook and subnotebook computers.
These devices feature internal synchronous rectification
for high efficiency and reduced component count. They
require no external Schottky diode. The internal 45mΩ
PMOS power switch and 55mΩ NMOS synchronous-rec-
tifier switch easily deliver continuous load currents up to
3A. The MAX1830 produces preset +2.5V, +1.8V, or
+1.5V output voltage or an adjustable output from +1.1V
to V
IN
. The MAX1831 produces preset +3.3V, +2.5V, and
+1.5V output voltages and an adjustable output from
+1.1V to V
IN.
They achieve efficiencies as high as 94%.
The MAX1830/MAX1831 use a unique current-mode,
constant-off-time, PWM control scheme, which includes
Idle Mode™ to maintain high efficiency during light-
load operation. The programmable constant-off-time
architecture sets switching frequencies up to 1MHz,
allowing the user to optimize performance trade-
offs between efficiency, output switching noise, compo-
nent size, and cost. Both devices are designed for con-
tinuous output currents up to 3A, an internal digital
soft-start to limit surge currents during startup, a 100%
duty cycle mode for low-dropout operation, and a
low-power shutdown mode that disconnects the input
from the output and reduces supply current below
1µA.The MAX1830/MAX1831 are available in 16-pin
QSOP packages.
For similar devices that provide continuous output
currents of 1A to 3A, refer to the MAX1644, MAX1623,
and MAX1742/MAX1842/MAX1843 data sheets.
o
±1.5% Output Accuracy
o
94% Efficiency
o
Internal PMOS/NMOS Switches
45mΩ/55mΩ On-Resistance at V
IN
= +4.5V
50mΩ/55mΩ On-Resistance at V
IN
= +3V
o
Output Voltages
+3.3V, +2.5V, or +1.5V Pin Selectable (MAX1831)
+2.5V, +1.8V, or +1.5V Pin Selectable (MAX1830)
+1.1V to V
IN
Adjustable (Both Devices)
o
+3V to +5.5V Input Voltage Range
o
750µA (max) Operating Supply Current
o
<1µA Shutdown Supply Current
o
Programmable Constant-Off-Time Operation
o
Up to 1MHz Switching Frequency
o
Idle Mode Operation at Light Loads
o
Thermal Shutdown
o
Internal Digital Soft-Start Inrush Current Limiting
o
100% Duty Cycle During Low-Dropout Operation
o
Output Short-Circuit Protection
o
16-Pin QSOP Package
Features
MAX1830/MAX1831
Ordering Information
PART
MAX1830EEE
MAX1831EEE
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
16 QSOP
Applications
5V or 3.3V to Low-Voltage Conversion
CPU I/O Supplies
Chipset Supplies
Notebook and Subnotebook Computers
Typical Configuration
INPUT
+3V TO
+5.5V
IN
LX
OUTPUT
+1.1V TO
V
IN
MAX1830
FB
MAX1831
V
CC
PGND
GND
SHDN
COMP
TOFF
FBSEL
REF
Pin Configuration appears at end of data sheet.
Idle Mode is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________
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.
3A, 1MHz, Low-Voltage, Step-Down Regulators with
Synchronous Rectification and Internal Switches
MAX1830/MAX1831
ABSOLUTE MAXIMUM RATINGS
V
CC
, IN,
SHDN
to GND ............................................-0.3V to +6V
IN to V
CC
.............................................................................±0.3V
GND to PGND.....................................................................±0.3V
COMP, FB, TOFF, FBSEL, REF to GND .....-0.3V to (V
CC
+ 0.3V)
LX Current (Note 1) ...............................................................5.1A
REF Short Circuit to GND Duration ............................Continuous
ESD Protection .....................................................................±2kV
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 14mW/°C above +70°C;
part mounted on 1in
2
of 1oz copper) .............................1.12W
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature ......................................................+150°C
Lead Temperature (soldering, 10s) ................................ +300°C
Note 1:
LX has internal clamp diodes to PGND and IN. Applications that forward bias the diode should take care not to exceed the IC’s
package power dissipation.
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
IN
= V
CC
= +3.3V, FBSEL = GND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Input Voltage
SYMBOL
V
IN
, V
CC
FBSEL = V
CC
V
IN
= +3V to +5.5V,
I
LOAD
= 0 to 3A,
V
FB
= V
OUT
Preset Output Voltage
V
OUT
V
IN
= +3.7V to +5.5V,
I
LOAD
= 0 to 3A,
V
FB
= V
OUT
Adjustable Output Voltage Range
AC Load Regulation Error
DC Load Regulation Error
Dropout Voltage
Reference Voltage
Reference Load Regulation
Current-Limit Threshold
Maximum Output RMS Current
Idle Mode Current Threshold
PMOS Switch On-Resistance
NMOS Switch On-Resistance
Switching Frequency
No-Load Supply Current
V
DO
V
REF
∆V
REF
I
LIMIT
I
OUT(RMS)
(Note 4)
I
IM
R
ON
,
P
R
ON
,
N
f
I
IN
+ I
CC
I
LX
= 0.5A
I
LX
= 0.5A
(Note 2)
V
FB
= 1.2V
325
V
IN
= 4.5V
V
IN
= 3V
V
IN
= 4.5V
V
IN
= 3V
0.2
0.6
45
50
55
55
I
REF
= -1µA to +10µA
4.0
V
CC
= V
IN
= +3V, I
LOAD
= 3A
1.089
FBSEL =
unconnected
FBSEL = REF
(MAX1830)
FBSEL = GND
FBSEL = REF
(MAX1831)
CONDITIONS
MIN
3.0
2.487
1.492
1.791
1.084
3.283
2.525
1.515
1.818
1.100
3.333
TYP
MAX
5.5
2.563
1.538
1.845
1.117
3.383
UNITS
V
V
V
CC
= V
IN
= +3V to +5.5V, I
LOAD
= 0,
FBSEL = GND
V
REF
2
0.4
150
1.100
0.5
4.8
V
IN
V
%
%
330
1.111
2
5.4
3.4
1.0
90
110
95
100
1
750
mV
V
mV
A
A
A
mΩ
MHz
µA
2
_______________________________________________________________________________________
3A, 1MHz, Low-Voltage, Step-Down Regulators with
Synchronous Rectification and Internal Switches
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
CC
= +3.3V, FBSEL = GND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
SHDN
= GND, into V
CC
and IN pins; LX = 0
or 3.3V
Shutdown Supply Current
SHDN
= GND, into IN with LX = 0
SHDN
= GND, into IN with LX = 3.3V
Thermal Shutdown Threshold
Undervoltage Lockout Threshold
FB Input Bias Current
Off-Time
Startup Off-Time
Minimum On-Time
Soft-Start Time (Note 3)
SHDN
Input Current
SHDN
Logic Input Low Voltage
SHDN
Logic Input High Voltage
FBSEL Input Current
FBSEL = GND
FBSEL = REF
FBSEL Logic Thresholds
FBSEL = unconnected
FBSEL = V
CC
0.9
0.7
✕
V
CC
- 0.2
V
CC
- 0.2
I
SHDN
V
IL
V
IH
2.0
-5
5
0.2
1.3
0.7
✕
V
CC
+ 0.2
V
CC
+ 0.2
SHDN
= 0 or V
CC
-0.5
t
ON
(Note 2)
0.40
3
✕
256
0.5
0.8
T
SHDN
V
UVLO
I
FB
t
OFF
Hysteresis = 15°C
V
IN
falling, hysteresis = 90mV
V
FB
= 1.2V
R
TOFF
= 110kΩ
R
TOFF
= 44kΩ
R
TOFF
= 440kΩ
1.8
0
0.85
0.3
3.0
MIN
TYP
0.2
0.2
0.1
165
2.6
70
1.00
0.4
3.9
4
✕
t
OFF
2.8
300
1.15
0.5
5.0
MAX
20
20
20
°C
V
nA
µs
µs
µs
µs
µs
cycles
µA
V
V
µA
V
V
V
V
µA
UNITS
MAX1830/MAX1831
ELECTRICAL CHARACTERISTICS
(V
IN
= V
CC
= +3.3V, FBSEL = GND,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 5)
PARAMETER
Input Voltage
SYMBOL
V
IN
, V
CC
FBSEL = V
CC
V
IN
= +3V to +5.5V,
I
LOAD
= 0 to 3A,
V
FB
= V
OUT
Preset Output Voltage
V
OUT
V
IN
= +3.7V to +5.5V,
I
LOAD
= 0 to 3A,
V
FB
= V
OUT
FBSEL =
unconnected
FBSEL = REF
(MAX1830)
FBSEL = GND
FBSEL = REF
(MAX1831)
CONDITIONS
MIN
3.0
2.475
1.485
1.782
1.078
3.267
TYP
MAX
5.5
2.575
1.545
1.854
1.122
3.399
UNITS
V
V
_______________________________________________________________________________________
3
3A, 1MHz, Low-Voltage, Step-Down Regulators with
Synchronous Rectification and Internal Switches
MAX1830/MAX1831
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
CC
= +3.3V, FBSEL = GND,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 5)
PARAMETER
Adjustable Output Voltage Range
Reference Voltage
Current-Limit Threshold
Idle Mode Current Threshold
PMOS Switch On-Resistance
NMOS Switch On-Resistance
No-Load Supply Current
FB Input Bias Current
Off-Time
V
REF
I
LIMIT
I
IM
R
ON
,
P
R
ON
,
N
I
IN
+ I
CC
I
FB
t
OFF
I
LX
= 0.5A
I
LX
= 0.5A
V
FB
= 1.2V
V
FB
= 1.2V
R
TOFF
= 110kΩ
0
0.8
V
IN
= 4.5V
V
IN
= +3V
V
IN
= 4.5V
V
IN
= +3V
SYMBOL
CONDITIONS
V
CC
= V
IN
= +3V to +5.5V, I
LOAD
= 0, FBSEL
= GND
MIN
V
REF
1.078
3.9
0.14
TYP
MAX
V
IN
1.122
5.4
1.0
90
110
95
100
750
360
1.2
µA
nA
µs
mΩ
UNITS
V
V
A
A
Note 2:
Note 3:
Note 4:
Note 5:
Not production tested.
Soft-start time is measured with respect to the number of cycles on LX.
This is a metal migration limit. Maximum output current may be limited by thermal capability to a lower value than this.
Specifications from 0°C to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT CURRENT
(V
IN
= 5.0V, L = 1.5µH)
MAX1830 toc01
EFFICIENCY vs. OUTPUT CURRENT
(V
IN
= 3.3V, L = 1.5µH)
MAX1830 toc02
EFFICIENCY vs. OUTPUT CURRENT
(f
PWM
= 300kHz)
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
V
OUT
= 1.8V
V
IN
= 3.3V
R
TOFF
= 160kΩ
L = 2.5µH
V
OUT
= 1.8V
V
IN
= 5.0V
R
TOFF
= 220kΩ
L = 5.2µH
MAX1830 toc03
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
0.001
0.01
0.1
1
V
OUT
= 1.8V
R
TOFF
= 75kΩ
V
OUT
= 1.5V
R
TOFF
= 82kΩ
V
OUT
= 3.3V
R
TOFF
= 39kΩ
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
V
OUT
= 2.5V
R
TOFF
= 39kΩ
V
OUT
= 1.8V
R
TOFF
= 51kΩ
V
OUT
= 1.5V
R
TOFF
= 62kΩ
100
10
50
0.001
0.01
0.1
1
10
50
0.001
0.01
0.1
1
10
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
4
_______________________________________________________________________________________
3A, 1MHz, Low-Voltage, Step-Down Regulators with
Synchronous Rectification and Internal Switches
Typical Operating Characteristics (continued)
(Circuit of Figure 1, T
A
= +25°C, unless otherwise noted.)
NORMALIZED OUTPUT ERROR
vs. OUTPUT CURRENT
MAX1830 toc04
MAX1830/MAX1831
SWITCHING FREQUENCY
vs. OUTPUT CURRENT
V
IN
= 5.0V,
V
OUT
= 1.5V, L = 1.5µH
MAX1830 toc05
STARTUP AND SHUTDOWN
MAX1830 toc06
0.10
NORMALIZED OUTPUT ERROR (%)
0.05
0
-0.05
-0.10
-0.15
-0.20
-0.25
0.001
V
IN
= 5.0V
V
OUT
= 1.5V
L = 1.5µH
V
IN
= 3.3V
V
OUT
= 1.5V
L = 1.5µH
1200
1000
FREQUENCY (kHz)
800
600
400
200
0
V
IN
= 3.3V,
V
OUT
= 1.5V, L = 1.5µH
I
IN
1A/div
V
SHDN
5V/div
V
OUT
1V/div
0
0.5
1.0
1.5
2.0
2.5
3.0
400µs/div
V
IN
= 3.3V, V
OUT
= 1.5V,
R
OUT
= 0.5Ω, R
TOFF
= 82kΩ, L = 1.5µH
0.01
0.1
1
10
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
LOAD-TRANSIENT RESPONSE
MAX1830 toc07
LINE-TRANSIENT RESPONSE
MAX1830 toc08
V
IN
2V/div
V
OUT
50mV/div
AC-COUPLE
0
I
OUT
2A/div
10µs/div
V
IN
= 3.3V, V
OUT
= 1.5V,
R
TOFF
= 82kΩ, L = 1.5µH, I
OUT
= 0.1A TO 3A
20µs/div
V
OUT
= 1.8V, I
OUT
= 1A,
R
TOFF
= 75kΩ, L = 1.5µH
V
OUT
50mV/div
AC-COUPLED
_______________________________________________________________________________________
5
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