Not Recommended for New Designs
This product was manufactured for Maxim by an outside wafer foundry
using a process that is no longer available. It is not recommended for
new designs. The data sheet remains available for existing users.
A Maxim replacement or an industry second-source m a y be available.
Please see the QuickView data sheet for this part or contact technical
support for assistance.
For further information, contact Maxim’s Applications Tech Support.
_______________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.
_______________________Applications
Distributed Power from High-Voltage Buses
High-Current, High-Voltage Step-Down Applications
Multiple-Output Buck Converter
MAX830–MAX833
5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators
________________________________________________________________
Maxim Integrated Products
1
TOP VIEW
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
VSW
VSW
VSW
VSW
VIN
VIN
VIN
VIN
MAX830
MAX831
MAX832
MAX833
GND
VC
GND
SHUT
(FB) SENSE
GND
ILIM
GND
Wide SO
Tj (MAX) = +125°C, θjA = +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).
__________________Pin Configuration
VIN
VC
VSW
100µF
GND
10k
0.047µF
OUTPUT
5V AT 1A
SENSE
100µH*
MBR350
470µF
INPUT
8V TO 30V
MAX831
STEP-DOWN CONVERTER
* CoilCraft DO3316-104
__________Typical Operating Circuit
Call toll free 1-800-998-8800 for free samples or literature.
19-0167; Rev 2; 6/95
___________________________Features
♦Input Range: Up to 30V
♦1A On-Chip Power Switch
♦ Adjustable Output (MAX830)
Fixed Outputs: 5V (MAX831)
3.3V (MAX832)
3V (MAX833)
♦100kHz Switching Frequency
♦Excellent Dynamic Characteristics
♦Few External Components
♦8mA Quiescent Current
♦16-Pin SO Package
♦Evaluation Kit Available
______________Ordering Information
PART TEMP. RANGE PIN-PACKAGE
MAX830CWE 0°C to +70°C 16 Wide SO
MAX832CWE 0°C to +70°C 16 Wide SO
MAX831CWE 0°C to +70°C 16 Wide SO
MAX833CWE 0°C to +70°C 16 Wide SO
EVALUATION KIT MANUAL
FOLLOWS DATA SHEET
MAX830–MAX833
5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators
2 _______________________________________________________________________________________
MAX830–MAX833
Input Voltage..................................................40V
Switch Voltage with Respect to Input Voltage................50V
Switch Voltage with Respect to GND
(VSW negative) (Note 1).....................................20V
FB/SENSE Voltage ...................................-0.3V, +10V
SHUT Voltage (not to exceed VIN)............................30V
ILIM 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
(VIN = 25V, TA= TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
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.
ABSOLUTE MAXIMUM RATINGS
PARAMETER CONDITIONS
Error-Amplifier Source Current VFB = 2.0V (MAX830) or
VSENSE = 2.0V
(MAX831/832/833)
MIN TYP MAX UNITS
100 140 225
Supply Current (Note 3)
ILIM open
mA
TA= +25°C
µATA= +25°C
Error-Amplifier Sink Current VFB = 2.5V (MAX830) or
VSENSE = 5.5V
(MAX831/832/833)
1.2 1.7 2.2
Input Supply Voltage Range 830V
0.6 1.0 1.7 mATA= +25°C
VIN = 25V, VSW = 0V 150
Switch-Off Leakage VIN = 30V, VSW = 0V 250 µA
811
V
IN ≤30V, VSENSE = 5.5V (MAX831/MAX832/
MAX833) or VFB = 2.5V (MAX830)
Minimum Supply Voltage (Note 5) Normal mode V
Startup mode 3.5 4.8
7.3 8.0
VSHUT = 0.1V (Note 4) 140 500 µA
1.2
Maximum Duty Cycle
Switch-Current Limit (Note 6)
85 90 %
0.8 A
Switching-Frequency Line Regulation 8V ≤VIN ≤30V 0.03 0.10 %/V
Error-Amplifier Transconductance
Error-Amplifier Voltage Gain 1V ≤VC≤4V 2000 V/V
3000 5000 9000 µmho
RLIM = 10kΩ(Note 7) TA= +25°C
RLIM = 7kΩ(Note 7)
TA= +25°C
TA= +25°C
Switch-On Voltage (Note 2) ISW = 0.2A 1.1 V
ISW = 1A 1.4
90 100 110
Switching Frequency VFB or VSENSE = 0V (Note 6) 85 120
20 kHz
TA= +25°C
TA= +25°C
MAX830–MAX833
5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators
_______________________________________________________________________________________ 3
MAX830–MAX833
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 25V, TA= TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
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 VCpin 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 VIN 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 VFB or VSENSE is less than
1.3V. Switch current limit is tested with VSENSE or VFB adjusted to give a 1µs minimum switch-on time.
Note 7:
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.
RI1A 7.6k 1k
LIM LIM
=×
+ΩΩ .
PARAMETER CONDITIONS
VCVoltage Temperature Coefficient
MAX831
MAX832
MIN TYP MAX UNIT
MAX833
0% duty cycle
MAX831
MAX832
MAX833
TA= +25°C
mV/°C
FB Bias Current 0.5 2.0 VReference Voltage
VREF (nominal = 2.21V) (MAX830)
TA= +25°C 1.5VCVoltage 0% duty cycle -4
4.85 5.00 5.15 V
V
3.20 3.30 3.40
µA
VSHUT = 5V
SENSE Voltage
10 20
VC= 2V 2.90 3.00 3.10
8V ≤VIN ≤30V
SHUT Current
0.005 0.020 %/VOutput Voltage Line Regulation
3.0 5.0 8.0
VSHUT = 0.1V (shutdown) 50
kΩ
µA
2.5 4.2 7.0SENSE Divider Resistance TA= +25°C 2.2 3.8 6.5
(shutdown) 0.10 0.20 0.50
%SENSE Voltage Tolerance (Note 8) VOUT (nominal) = 5V (MAX831),
3.3V (MAX832), or 3V (MAX833) ±0.5 ±2.0
2.155 2.21 2.265
SHUT Threshold V
%
Reference Voltage Tolerance
(Notes 8, 9) ±0.5 ±1.5TA= +25°C
VFB = VREF (MAX830)
VC= 2V (MAX830) (Note 9)
±1.0 ±2.5
Typical value only. Minimum to maximum deviation in current limit will be ±30%,
comparable to that with ILIM pin open.
±0.5 ±3.0
MAX830–MAX833
5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators
4 _______________________________________________________________________________________
MAX830–MAX833
______________________________________________________________Pin Description
PIN FUNCTION
11
5, 7,
10, 12
1, 2,
3, 4
6
9 Shutdown is achieved by pulling SHUT low. Leave SHUT floating for normal operation.
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. VCcan 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.
VIN supplies power to the internal circuitry and also connects to the collector of the internal power switch.
VIN must be bypassed with a low-ESR capacitor, typically 100µF.
Switch-current limit can be reduced by connecting an external resistor (RLIM) from ILIM to GND
(See Note 7 in
Electrical Characteristics
). Leave ILIM floating for maximum current limit.
NAME
VC
GND
VIN
ILIM
SHUT
__________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, Tj, 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 Tj= +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 Tj= +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 ILIM pin to
GND. With no external resistor, the preset switch cur-
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 TA= +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 IPEAK.
For highest efficiency, the inductor series resistance
should be 0.4Ωor less. IPEAK and ILOAD are related by
the following formula: [VOUT x (VIN - VOUT)]
IPEAK = ILOAD + ——————————
VIN x L x 200,000
Example: MAX830 with VIN = 30V, VOUT = 15V,
ILOAD = 0.5A continuous, L = 100µH and
TA= +70°C:
IPEAK = 0.86A (which is below 1.2A (min)
preset switch current limit);
and from Table 1:
maximum ILOAD allowed = 0.8A continuous
(i.e., operation is safe).
SENSE
(MAX831/
2/3)
8
For the MAX831/MAX832/MAX833, SENSE input is the internal error amplifier’s input, and should be
directly connected to VOUT. SENSE also aids current limiting by reducing oscillator frequency when VOUT
is low.
VSW
13, 14,
15, 16 Internal power switch output (rated for 1A load current)
FB
(MAX830)
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 VOUT and GND (Figure 1). The output voltage, during regulation, will
be that value that forces 2.21V (VREF) at the FB pin.
MAX830–MAX833
5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators
_______________________________________________________________________________________ 5
_________________________________________________________________________________________________
5
Table 1. MAX830 Maximum Load Current (continuous with
q
jA = +55°C/W) vs.
Output Voltage and Ambient Temperature
OUTPUT VOLTAGE CONTINUOUS LOAD CURRENT
Up to 10V 1A 1A 1A
10V to 15V 1A 1A 0.8A
15V to 20V 1A 0.8A 0.7A
20V to 25V 0.8A 0.7A 0.6A
Table 2. MAX831/MAX832/MAX833 Maximum Load Current (continuous with
q
jA = +55°C/W) vs. Ambient Temperature
OUTPUT VOLTAGE CONTINUOUS LOAD CURRENT
Fixed:
5V, 3.3V or 3V 1A 1A 1A
TA= +25°C TA= +45°C TA= +70°C
TA= +25°C TA= +45°C TA= +70°C
VIN
VC
VSW
100µF
GND
10k
0.047µF
VOUT
FB
100µH
MBR350
470µF
R1
VOUT = [1 + R1 ] x 2.21V
R2
R2
INPUT
UP TO 30V
MAX830
STEP-DOWN CONVERTER
Figure 1. MAX830 Typical Operating Circuit
