19-0167; Rev 2; 6/95
5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators
_______________General Description
The MAX830/MAX831/MAX832/MAX833 are monolithic,
bipolar, pulse-width-modulation (PWM), switch-mode, step-
down DC-DC regulators. Each is rated at 1A. Very few
external components are needed for standard operation
because the power switch, oscillator, feedback, and control
circuitry are all on-chip. Employing a classic buck topology,
these regulators perform high-current step-down functions.
These regulators have excellent dynamic and transient
response characteristics, while featuring cycle-by-cycle cur-
rent limiting to protect against overcurrent faults and short-
circuit output faults. They have a wide 8V to 30V input
range. Outputs for the MAX831/MAX832/MAX833 are fixed
at 5V/3.3V/3V, respectively. The MAX830 output is
adjustable.
Available in 16-pin SO packages, the MAX830–MAX833
have a preset 100kHz oscillator frequency. In addition,
the preset current limit and micropower shutdown can be
externally controlled. See the MAX724/MAX726 data
sheet for more applications information.
UAL
IT MAN
TION K
A
EET
EVALU
ATA SH
OWS D
FOLL
___________________________Features
o
Input Range: Up to 30V
o
1A On-Chip Power Switch
o
Adjustable Output (MAX830)
Fixed Outputs: 5V (MAX831)
3.3V (MAX832)
3V (MAX833)
o
100kHz Switching Frequency
o
Excellent Dynamic Characteristics
o
Few External Components
o
8mA Quiescent Current
o
16-Pin SO Package
o
Evaluation Kit Available
MAX830–MAX833
______________Ordering Information
PART
MAX830CWE
MAX831CWE
MAX832CWE
MAX833CWE
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
PIN-PACKAGE
16 Wide SO
16 Wide SO
16 Wide SO
16 Wide SO
_______________________Applications
Distributed Power from High-Voltage Buses
High-Current, High-Voltage Step-Down Applications
Multiple-Output Buck Converter
__________Typical Operating Circuit
__________________Pin Configuration
TOP VIEW
INPUT
8V TO 30V
VIN
100µF
VSW
100µH*
OUTPUT
5V AT 1A
V
IN
1
V
IN
2
V
IN
3
16
V
SW
15
V
SW
14
V
SW
MAX831
VC
10k
0.047µF
SENSE
MBR350
V
IN
4
GND
5
470µF
GND
I
LIM
6
GND
7
(FB) SENSE
8
MAX830
MAX831
MAX832
MAX833
13
V
SW
12
GND
11
V
C
10
GND
9
SHUT
Wide SO
T
j
(MAX) = +125°C,
θ
jA =
+55°C/W*
( ) ARE FOR MAX830
* THIS THERMAL RESISTANCE NUMBER IS WITH THE DEVICE WELL MOUNTED
ON 1 oz. COPPER WITH THERMAL PASTE BETWEEN THE IC AND THE
UNDERLYING GROUND PLANE. LOWER THERMAL RESISTANCE IS POSSIBLE
(SEE APPLICATIONS SECTION).
STEP-DOWN CONVERTER
* CoilCraft DO3316-104
________________________________________________________________
Maxim Integrated Products
1
Call toll free 1-800-998-8800 for free samples or literature.
5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators
MAX830–MAX833
ABSOLUTE MAXIMUM RATINGS
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40V
Switch Voltage with Respect to Input Voltage. . . . . . . . . . . . . . . . 50V
Switch Voltage with Respect to GND
(V
SW
negative) (Note 1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20V
FB/SENSE Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V, +10V
SHUT Voltage (not to exceed V
IN
) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30V
Note 1:
Do not exceed switch-to-input voltage limitation.
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.
I
LIM
Voltage (forced). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5V
Operating Temperature Range. . . . . . . . . . . . . . . . . . . . . 0°C to +70°C
Junction Temperature Range . . . . . . . . . . . . . . . . . . . . . 0°C to +125°C
Storage Temperature Range . . . . . . . . . . . . . . . . . . . -65°C to +160°C
Lead Temperature (soldering, 10sec). . . . . . . . . . . . . . . . . . . . +300°C
ELECTRICAL CHARACTERISTICS
(V
IN
= 25V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Input Supply Voltage Range
Switch-On Voltage (Note 2)
Switch-Off Leakage
I
SW
= 0.2A
I
SW
= 1A
V
IN
= 25V, V
SW
= 0V
V
IN
= 30V, V
SW
= 0V
T
A
= +25°C
8
140
7.3
3.5
1.2
T
A
= +25°C
85
T
A
= +25°C
Switching Frequency
V
FB
or V
SENSE
= 0V (Note 6)
Switching-Frequency Line Regulation
Error-Amplifier Voltage Gain
Error-Amplifier Transconductance
Error-Amplifier Source Current
V
FB
= 2.0V (MAX830) or
V
SENSE
= 2.0V
(MAX831/832/833)
V
FB
= 2.5V (MAX830) or
V
SENSE
= 5.5V
(MAX831/832/833)
8V
≤
V
IN
≤
30V
1V
≤
V
C
≤
4V
T
A
= +25°C
T
A
= +25°C
T
A
= +25°C
3000
100
T
A
= +25°C
90
85
20
0.03
2000
5000
140
9000
225
0.10
%/V
V/V
µmho
µA
1.7
1.2
0.8
90
100
110
120
kHz
%
CONDITIONS
MIN
8
TYP
MAX
30
1.1
1.4
150
250
11
500
8.0
4.8
2.2
A
UNITS
V
V
µA
mA
µA
V
Supply Current (Note 3)
V
IN
≤
30V, V
SENSE
= 5.5V (MAX831/MAX832/
MAX833) or V
FB
= 2.5V (MAX830)
V
SHUT
= 0.1V (Note 4)
Minimum Supply Voltage (Note 5)
Normal mode
Startup mode
I
LIM
open
R
LIM
= 10kΩ (Note 7)
R
LIM
= 7kΩ (Note 7)
Switch-Current Limit (Note 6)
Maximum Duty Cycle
Error-Amplifier Sink Current
T
A
= +25°C
0.6
1.0
1.7
mA
2
_______________________________________________________________________________________
5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 25V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SENSE Voltage
V
C
= 2V
CONDITIONS
MAX831
MAX832
MAX833
MAX831
SENSE Divider Resistance
T
A
= +25°C
MAX832
MAX833
SENSE Voltage Tolerance (Note 8)
FB Bias Current
Reference Voltage
Reference Voltage Tolerance
(Notes 8, 9)
Output Voltage Line Regulation
V
C
Voltage
V
C
Voltage Temperature Coefficient
SHUT Current
SHUT Threshold
V
OUT
(nominal) = 5V (MAX831),
3.3V (MAX832), or 3V (MAX833)
V
FB
= V
REF
(MAX830)
V
C
= 2V (MAX830) (Note 9)
T
A
= +25°C
V
REF
(nominal = 2.21V) (MAX830)
±1.0
8V
≤
V
IN
≤
30V
0% duty cycle
0% duty cycle
V
SHUT
= 5V
V
SHUT
= 0.1V (shutdown)
(shutdown)
0.10
0.20
T
A
= +25°C
0.005
1.5
-4
10
20
50
0.50
±2.5
0.020
%/V
V
mV/°C
µA
V
2.155
T
A
= +25°C
MIN
4.85
3.20
2.90
3.0
2.5
2.2
TYP
5.00
3.30
3.00
5.0
4.2
3.8
±0.5
±0.5
0.5
2.21
±0.5
MAX
5.15
3.40
3.10
8.0
7.0
6.5
±2.0
±3.0
2.0
2.265
±1.5
%
%
µA
V
kΩ
V
UNIT
MAX830–MAX833
MAX830–MAX833
Note 2:
For switch currents between 0.2A and 1A, maximum switch-on voltage can be calculated via linear interpolation.
Note 3:
By setting the SENSE pin to 5.5V (or the FB pin to 2.5V), the V
C
pin is forced to its low clamp level and the switch duty cycle
is forced to zero, approximating the zero load condition.
Note 4:
Device shut down. Switch leakage current not included.
Note 5:
For proper regulation, total voltage from V
IN
to GND must be
≥
8V after start-up. During start-up mode, device is switching
but not regulating.
Note 6:
To avoid extremely short switch-on times, the switch frequency is internally scaled down when V
FB
or V
SENSE
is less than
1.3V. Switch current limit is tested with V
SENSE
or V
FB
adjusted to give a 1µs minimum switch-on time.
Note 7:
R
LIM
=
LIM
×
7.6k
Ω +
1k
Ω
.
1A
I
Typical value only. Minimum to maximum deviation in current limit will be ±30%,
comparable to that with I
LIM
pin open.
Note 8:
All conditions of input voltage, output voltage, temperature, and load current.
Note 9:
FB is at the reference voltage when the MAX830 output voltage is in regulation.
_______________________________________________________________________________________
3
5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators
MAX830–MAX833
______________________________________________________________Pin Description
PIN
NAME
SENSE
(MAX831/
2/3)
FB
(MAX830)
11
5, 7,
10, 12
13, 14,
15, 16
1, 2,
3, 4
6
9
V
C
GND
V
SW
V
IN
I
LIM
SHUT
FUNCTION
For the MAX831/MAX832/MAX833, SENSE input is the internal error amplifier’s input, and should be
directly connected to V
OUT
. SENSE also aids current limiting by reducing oscillator frequency when V
OUT
is low.
For the MAX830, the FB input is the internal error amplifier's input, and should be connected to the mid-
point of a potential divider between V
OUT
and GND (Figure 1). The output voltage, during regulation, will
be that value that forces 2.21V (V
REF
) at the FB pin.
Error-amplifier output. A series RC network connected to this pin compensates the device. Output swing
is limited to about 5.8V in the positive direction and -0.7V in the negative direction. V
C
can also synchro-
nize the device to an external TTL clock in the 115kHz to 170kHz range.
Ground requires a short, low-noise connection to ensure good load regulation. The internal reference is referred
to GND, so errors at this pin are multiplied by the error amplifier. Use thick copper for low thermal resistance.
Internal power switch output (rated for 1A load current)
V
IN
supplies power to the internal circuitry and also connects to the collector of the internal power switch.
V
IN
must be bypassed with a low-ESR capacitor, typically 100µF.
Switch-current limit can be reduced by connecting an external resistor (R
LIM
) from I
LIM
to GND
(See Note 7 in
Electrical Characteristics).
Leave I
LIM
floating for maximum current limit.
Shutdown is achieved by pulling SHUT low. Leave SHUT floating for normal operation.
8
__________Applications Information
Although the MAX830–MAX833 are high-efficiency
step-down voltage converters, certain precautions are
required to avoid excessive chip temperature (the
absolute maximum rating for this parameter, T
j
, is
+125°C). The 16-pin SO package has thermal resis-
tance of +55°C/W when mounted properly; this limits
continuous chip power dissipation to the 1W range.
When installing these chips:
1) Use wide and, if possible, thick copper traces to
connect the leads (especially the GND pins) to
reduce thermal resistance.
2) Bond the package firmly to the board or use a clip-
style heatsink. A very small drop of thermal paste
between the chip package and the copper ground
plane is also helpful.
3) Confirm that the range of device operation is such
that the chip temperature does not exceed the
allowed maximum of T
j
= +125°C. This can be
determined from Tables 1 and 2.
Tables 1 and 2 show numbers for maximum allowed
load current based on not exceeding the T
j
= +125°C
limit. If the input voltage range, ambient temperature,
and/or output voltage setting allow for an unsafe level
of load current, limit the load current to a safe value by
connecting the appropriate resistor from the I
LIM
pin to
GND. With no external resistor, the preset switch cur-
4
rent limit (typically 1.7A) will limit the load current to
about 1.3A. Table 1 shows safe operating load cur-
rents for the MAX830 for various values of input and
output voltage and at three different ambient tempera-
tures of T
A
= +25°C, +45°C, and +70°C, respectively.
Table 2 shows the same information, but for the fixed
output voltage MAX831, MAX832, and MAX833.
When consulting these tables, note that power surges
of less than 30sec need not be considered from a ther-
mal standpoint. It is important for proper regulation,
however, that a power surge not require a peak switch
current exceeding the 1.2A (min) switch current limit.
Also, the inductor’s current rating should exceed I
PEAK
.
For highest efficiency, the inductor series resistance
should be 0.4Ω or less. I
PEAK
and I
LOAD
are related by
the following formula:
[V
OUT
x (V
IN
- V
OUT
)]
I
PEAK
= I
LOAD
+ ——————————
V
IN
x L x 200,000
Example: MAX830 with V
IN
= 30V, V
OUT
= 15V,
I
LOAD
= 0.5A continuous, L = 100µH and
T
A
= +70°C:
I
PEAK
= 0.86A (which is below 1.2A (min)
preset switch current limit);
and from Table 1:
maximum I
LOAD
allowed = 0.8A continuous
(i.e., operation is safe).
_______________________________________________________________________________________
5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators
Table 1. MAX830 Maximum Load Current (continuous with
q
jA
= +55°C/W) vs.
Output Voltage and Ambient Temperature
OUTPUT VOLTAGE
Up to 10V
10V to 15V
15V to 20V
20V to 25V
CONTINUOUS LOAD CURRENT
T
A
= +25°C
1A
1A
1A
0.8A
T
A
= +45°C
1A
1A
0.8A
0.7A
T
A
= +70°C
1A
0.8A
0.7A
0.6A
MAX830–MAX833
Table 2. MAX831/MAX832/MAX833 Maximum Load Current (continuous with
q
jA
= +55°C/W) vs. Ambient Temperature
OUTPUT VOLTAGE
Fixed:
5V, 3.3V or 3V
CONTINUOUS LOAD CURRENT
T
A
= +25°C
1A
T
A
= +45°C
1A
T
A
= +70°C
1A
INPUT
UP TO 30V
VIN
100µF
VSW
100µH
V
OUT
MBR350
MAX830
VC
10k
GND
0.047µF
FB
R1
470µF
R2
V
OUT
= 1 + R1
R2
[
]
x 2.21V
STEP-DOWN CONVERTER
Figure 1. MAX830 Typical Operating Circuit
_________________________________________________________________________________________________
_______________________________________________________________________________________
5
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