Rainbow Electronics MAX833 User Manual

19-0167; Rev 2; 6/95

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

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, step­down 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 cur­rent limiting to protect against overcurrent faults and short­circuit 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

___________________________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
♦ 8mAQuiescent Current
♦ 16-Pin SOPackage
♦ Evaluation Kit Available

______________Ordering Information

PART TEMP. RANGE PIN-PACKAGE

MAX830CWE 0°C to +70°C 16 Wide SO
MAX831CWE 0°C to +70°C 16 Wide SO
MAX832CWE 0°C to +70°C 16 Wide SO
MAX833CWE 0°C to +70°C 16 Wide SO

MAX830–MAX833

__________Typical Operating Circuit

INPUT

8V TO 30V



100µF

10k

0.047µF

* CoilCraft DO3316-104

V

V

IN

C

MAX831



GND

V

SENSE

SW

100µH*

MBR350

STEP-DOWN CONVERTER

________________________________________________________________

OUTPUT

5V AT 1A

470µF

__________________Pin Configuration

TOP VIEW

V

IN

1

V

2

IN

V

IN

3

V

IN

MAX830

4

GND

I

GND

(FB) SENSE

( ) 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).

MAX831

5

MAX832
MAX833

6

LIM

7
8

Wide SO

Tj (

= +125°C, θ

MAX)

Maxim Integrated Products

Call toll free 1-800-998-8800 for free samples or literature.

jA =

V

SW

16

V

15

SW

V

14

SW

V

13

SW

GND

12

V

11

C

GND

10

SHUT

9

+55°C/W*

1

5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators

ABSOLUTE MAXIMUM RATINGS

Input Voltage..................................................40V

Switch Voltage with Respect to Input Voltage................50V

Switch Voltage with Respect to GND

negative) (Note 1).....................................20V

(V

SW

FB/SENSE Voltage ...................................-0.3V, +10V

SHUT Voltage (not to exceed V

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.

)............................30V

IN

ELECTRICAL CHARACTERISTICS

(VIN= 25V, TA= T

MAX830–MAX833

MAX830–MAX833

Input Supply Voltage Range 830V
Switch-On Voltage (Note 2)

Switch-Off Leakage

Supply Current (Note 3)

Minimum Supply Voltage (Note 5)

Switch-Current Limit (Note 6)

Maximum Duty Cycle

Switching Frequency

Switching-Frequency Line Regulation 8V ≤ VIN≤ 30V 0.03 0.10 %/V
Error-Amplifier Voltage Gain 1V ≤ VC≤ 4V 2000 V/V
Error-Amplifier Transconductance

Error-Amplifier Source Current

Error-Amplifier Sink Current

to T

MIN

PARAMETER CONDITIONS

, unless otherwise noted. Typical values are at TA = +25°C.)

MAX

ISW= 0.2A 1.1
ISW= 1A 1.4
VIN= 25V, VSW= 0V 150
VIN= 30V, VSW= 0V 250

VIN≤ 30V, V
MAX833) or V

V

= 0.1V (Note 4) 140 500 µA

SHUT

Normal mode
Startup mode 3.5 4.8
I

open

LIM

R

= 10kΩ (Note 7)

LIM

R

= 7kΩ (Note 7)

LIM

VFBor V

SENSE

VFB= 2.0V (MAX830) or

= 2.0V

V

SENSE

(MAX831/832/833)
VFB= 2.5V (MAX830) or

= 5.5V

V

SENSE

(MAX831/832/833)

= 5.5V (MAX831/MAX832/

SENSE

= 2.5V (MAX830)

FB

= 0V (Note 6)

Voltage (forced)..........................................5.5V

I

LIM

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

MIN TYP MAX UNITS

V

TA= +25°C

TA= +25°C

TA= +25°C

TA= +25°C

TA= +25°C
TA= +25°C

811

7.3 8.0

1.2 1.7 2.2

1.2

0.8
85 90 %
90 100 110
85 120

20

3000 5000 9000 µmho

100 140 225

0.6 1.0 1.7 mATA= +25°C

µA

mA

V

A

kHz

µATA= +25°C

2 _______________________________________________________________________________________

5V/3.3V/3V/Adjustable-Output, 1A,

Step-Down, PWM, Switch-Mode DC-DC Regulators

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 25V, TA= T

PARAMETER CONDITIONS

SENSE Voltage

FB Bias Current 0.5 2.0

Reference Voltage Tolerance
(Notes 8, 9)

VCVoltage Temperature Coefficient

SHUT Current

SHUT Threshold V

MIN

to T

, unless otherwise noted. Typical values are at TA = +25°C.)

MAX

VC= 2V

V

(nominal) = 5V (MAX831),

OUT

3.3V (MAX832), or 3V (MAX833)
VFB= V

VC= 2V (MAX830) (Note 9)

V

REF

8V ≤ VIN≤ 30V
0% duty cycle
0% duty cycle -4
V

SHUT

V

SHUT

(shutdown) 0.10 0.20 0.50

(MAX830)

REF

(nominal = 2.21V) (MAX830)

= 5V
= 0.1V (shutdown) 50

MAX831
MAX832
MAX833
MAX831
MAX832
MAX833
TA= +25°C

TA= +25°C 1.5VCVoltage

MIN TYP MAX UNIT

4.85 5.00 5.15

3.20 3.30 3.40

2.90 3.00 3.10

3.0 5.0 8.0

2.5 4.2 7.0SENSE Divider Resistance TA= +25°C

2.2 3.8 6.5
±0.5 ±2.0
±0.5 ±3.0

2.155 2.21 2.265
±0.5 ±1.5TA= +25°C

±1.0 ±2.5

0.005 0.020 %/VOutput Voltage Line Regulation

mV/°C

10 20

V

kΩ

%SENSE Voltage Tolerance (Note 8)

µA

VReference Voltage

%

V

µA

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

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

but not regulating.

Note 6: To avoid extremely short switch-on times, the switch frequency is internally scaled down when V

1.3V. Switch current limit is tested with V



I

LIM

R

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.

=×



LIM

1A





7.6k 1k




_______________________________________________________________________________________ 3

Typical value only. Minimum to maximum deviation in current limit will be ±30%,

+ΩΩ .

comparable to that with I

to GND must be ≥ 8V after start-up. During start-up mode, device is switching

IN

or VFBadjusted to give a 1µs minimum switch-on time.

SENSE

pin is forced to its low clamp level and the switch duty cycle

C

or V

FB

pin open.

LIM

SENSE

is less than

5V/3.3V/3V/Adjustable-Output, 1A,
Step-Down, PWM, Switch-Mode DC-DC Regulators

______________________________________________________________Pin Description

PIN FUNCTION

11

5, 7,

10, 12
13, 14,

MAX830–MAX833

MAX830–MAX833

15, 16

1, 2,

3, 4

__________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 resis­tance 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 clip­style 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 I
GND. With no external resistor, the preset switch cur-

NAME

SENSE

(MAX831/

8

6
9 Shutdown is achieved by pulling SHUT low. Leave SHUT floating for normal operation.

2/3)

FB

(MAX830)

V

GND

V

V

I

LIM

SHUT

For the MAX831/MAX832/MAX833, SENSE input is the internal error amplifier’s input, and should be
directly connected to V
is low.

For the MAX830, the FB input is the internal error amplifier's input, and should be connected to the mid­point of a potential divider between V
be that value that forces 2.21V (V

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

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)

SW

VINsupplies power to the internal circuitry and also connects to the collector of the internal power switch.

IN

must be bypassed with a low-ESR capacitor, typically 100µF.

V

IN

Switch-current limit can be reduced by connecting an external resistor (R
(See Note 7 in

Electrical Characteristics

. SENSE also aids current limiting by reducing oscillator frequency when V

OUT

and GND (Figure 1). The output voltage, during regulation, will

OUT

) at the FB pin.

REF

) from I

). Leave I

floating for maximum current limit.

LIM

LIM

LIM

rent limit (typically 1.7A) will limit the load current to
about 1.3A. Table 1 shows safe operating load cur­rents for the MAX830 for various values of input and
output voltage and at three different ambient tempera­tures 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 ther­mal 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
For highest efficiency, the inductor series resistance
should be 0.4Ω or less. I

PEAK

and I

the following formula:

[V

x (V

I

PEAK

= I

LOAD

OUT

+ ——————————

VINx L x 200,000

Example: MAX830 with VIN= 30V, V

I

= 0.5A continuous, L = 100µH and

LOAD

TA= +70°C:
I

= 0.86A (which is below 1.2A (min)

PEAK

preset switch current limit);
and from Table 1:

LIM

pin to

maximum I
(i.e., operation is safe).

allowed = 0.8A continuous

LOAD

can also synchro-

C

to GND

are related by

LOAD

- V

IN

OUT

)]

OUT

= 15V,

OUT

PEAK

.

4 _______________________________________________________________________________________

5V/3.3V/3V/Adjustable-Output, 1A,

q

q

Step-Down, PWM, Switch-Mode DC-DC Regulators

Table 1. MAX830 Maximum Load Current (continuous with

Output Voltage and Ambient Temperature

OUTPUT VOLTAGE

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

TA= +25°C TA= +45°C TA= +70°C

CONTINUOUS LOAD CURRENT

Table 2. MAX831/MAX832/MAX833 Maximum Load Current (continuous with

= +55°C/W) vs. Ambient Temperature

jA

OUTPUT VOLTAGE

Fixed:

5V, 3.3V or 3V

TA= +25°C TA= +45°C TA= +70°C

1A 1A 1A

CONTINUOUS LOAD CURRENT

= +55°C/W) vs.

jA

MAX830–MAX833

INPUT

UP TO 30V



100µF

10k

Figure 1. MAX830 Typical Operating Circuit

_________________________________________________________________________________________________

_______________________________________________________________________________________ 5

V

MAX830



GND

SW

FB



V

IN

V

C

0.047µF

STEP-DOWN CONVERTER

100µH

MBR350

R1

=

1 +

V

OUT

[

R2

]

R1

R2

x 2.21V

V

OUT

470µF



5