AMC2576-ADJDDT - ADD Microtech Inc.

AMC DOC. #:AMC2576_B

November 2002

Copyright  2002, ADD Microtech Corp. 1 www.addmtek.com

DESCRIPTION FEATURES

The AMC2576 series is a step-down switching regulator with

all the required active functions. It is capable of driving 3A load

with excellent line and load regulations. These devices are

available in fixed output voltages of 3.3V, 5V, and an adjustable

output versi on.

The AMC2576 series offers a high-efficiency replacement for

popular three-terminal linear regulators. It requires only a

minimum number of external components. Substantially, it

reduces not only the area of board size but also the size of the

heat sink. In some cases, no heat sink is required.

The ± 4% tolerance on output voltage within specified input

voltages and output load conditions is guaranteed. T he

oscillator frequency accuracy is within ±10%. External

shutdown is included, featuring 70µA(typical) standby current.

The output switch includes cycle-by-cycle current limitation, as

well as thermal shutdown for full protection under fault

conditions.

! Guaranteed 3A output current

! 3.3V, 5V and adjustable output versions

! Wide input voltage range, up to 40V

! Internal oscillator of 5 2 KHz fixed frequency

! Wide adjustable version output voltage range,

from 1.23V to 37V ±4% max over line and

load conditions

# Low standby current, typ. 70µA, at shutdown

mode

# Requires only 4 external components

# Thermal shut down and current limit protection

# P+ Product enhancement tested

APPLICATIONS PACKAGE PIN OUT

! LCD Monitors

! ADD-ON Cards Switching Regulators

! High Efficiency Step-Down Regulators

! Efficient Pre-regulator for Linear

Regulators

$ Voltage Options:

AMC2576-3.3

AMC2576-5.0 – 3.3V Fixed

– 5.0V Fixed

AMC2576-ADJ – Adjustable Output

ORDER INFORMATION

Plastic TO-220 Plastic TO-220B Plastic TO-263

Temperature

Range P 5-pin PB 5-pin DD 5-pin

AMC2576-ADJP AMC2576-ADJPB AMC2576-ADJDD

-40°C≤ TJ ≤ 125°C AMC2576-X.XP AMC2576-X.XPB AMC2576-X.XDD

Note: All surface-mount packages are available in Tape & Reel. Append the letter “T” to part number (i.e.

AMC2576-X.XDDT).

AMC2576

3A STEP DOWN VOLTAGE REGULATOR



A

AA

ADD MICROTECH CORP.

5-Pin Plastic TO-263

Surface Mount

(To p View)

5-Pin Plastic

TO-220B

5-Pin Plastic TO-220

(Top View)

5. Enable

2. VOUT

1. VIN

4. FB

3. GND

5. Enable

3. GND

2. VOUT

1. VIN

4. FB

(

Side View

)

5. Enable

2. VOUT

1. VIN

4. FB

3. GND

AM C DOC. #: AMC2576_B AMC2576

November 2002

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TYPICAL APPLICATION

Figure 1. Fixed Output Voltage Versions

COUT

1000µF

OUTPUT

L1

100

µ

H

AMC2576-X.X

1

35

2

4

VIN

VOUT

FB

GND ENABLE

CIN

100µF

7V – 40V

DC INPUT

Figure 2. Adjustable Output Vo ltage Versions

R2

VOUT = VREF ( 1 + R1 )

VOUT

R2 = R1 ( VREF − 1 )

Where VREF = 1.23V, R1 between 1K and 5K

OUTPUT

COUT

1000µF

L1

100

µ

H

5

CIN

100µF

7V – 40V

DC INPUT

R2

R1

3

AMC2576-ADJ

2

4

VIN VOUT

FB

GND ENABLE

1

AM C DOC. #: AMC2576_B AMC2576

November 2002

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ABSOLUTE MAXIMUM RATINGS (Note 1)

Input Voltage, VIN 45V

ENABLE Pin Input Voltage -0.3V ≤ V ≤ VIN

Ope rating Junction Te mperature, TJ 150°C

Storage Temperature Range -65°C to 150°C

Lead Temperature (soldiering, 10 seconds) 260°C

Note 1: Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground.

Currents are positive into, negative out of the specified terminal.

RECOMMENDED OPERATING RATINGS

Temperature Range -40°C ≤ TJ ≤ 125°C

Input Voltage, VIN 40V(Max.)

THERMAL DATA

P,PB, DD PACKAGE:

Thermal Resistance-Junction to Tab, θJT 3.0°C /W

Thermal Resistance-Junction to Ambient, θJA 45°C /W

Junct ion Temperat ure Calculation: TJ = T A + (PD × θ JA).

The θJA numbers are guidelines for the thermal performance of the device/pc-board system.

All of the above assume no ambient airflow.

BLOCK DIAGRAM

VI

N

1

2

4

3

5

FB

GND

VOUT

Regulator

With

Enable

Comparator

52KHz

Oscillator

Driver

Thermal Shutdow n

&

Current Limit

ENABLE

Reset

1.23V

Reference

R1*

R2*

Error

Amplifier

VOUT = 3.3V : R2/R1 = 1.7

VOUT = 5.0V : R2/R1 = 3.1

VOUT = Adjustable

: R2 = 0

R1 = Open

AM C DOC. #: AMC2576_B AMC2576

November 2002

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DC ELECTRICAL CHARACTERISTICS

Unless otherwise specified, these specifications apply VIN = 12V, ILOAD = 0.5A and the operating ambient

temperatures TJ = 25°C. AMC2576

Parameter Symbol Test Co nd itions Min Typ Max Units

AMC2576-3.3 3.234 3.300 3.366

Output Voltage

(Note 1) AMC2576-5.0 VOUT Te st circuit of Figure 1 4.900 5.000 5.100 V

AMC2576-3.3 6V ≤VIN ≤ 40V 3.168 3.300 3.432

Output Voltage

(Note 1) AMC2576-5.0 VOUT 0.5A ≤ ILOAD ≤ 3A

Test circuit of Figure 1 8V ≤VIN ≤ 40V 4.800 5.000 5.200 V

AMC2576-3.3 6V ≤VIN ≤ 40V 3.135 3.300 3.482

Output Voltage

(Note 1) AMC2576-5.0 VOUT 0.5A ≤ ILOAD ≤ 3A,

-40°C ≤ TJ ≤ 125°C

Test circuit of Figure 1 8V ≤VIN ≤ 40V 4.750 5.000 5.250 V

Feedback Voltage

(Note 1) AMC2576-ADJ VOUTFB Test circuit of Figure 2 VOUT = 5V 1.217 1.230 1.243 V

Feedback Voltage

(Note 1) AMC2576-ADJ VOUTFB 8V ≤VIN ≤ 40V, VOUT = 5V,

Test c ircuit of Figure 2 0.5A ≤ ILOAD ≤ 3A 1.193 1.230 1.267 V

Feedback Voltage

(Note 1) AMC2576-ADJ VOUTFB 8V ≤VIN ≤ 40V, VOUT = 5V,

Test c ircuit of Figure 2 0.5A ≤ ILOAD ≤ 3A,

-40°C ≤ TJ ≤ 125°C 1.180 1.230 1.286 V

AMC2576-3.3

75

AMC2576-5.0 ILOAD = 3A 77

Efficiency

AMC2576-ADJ



ILOAD = 3A, VOUT = 5V 77

%

TJ = 25°C 47 52 58

Oscillator Frequency fOSC (Note 2) -40OC ≤ TJ ≤ 125°C 42 52 63

kHz

Quiescent Current IQ (Note 3) 5 10 mA

Standby Current ISTBY ENABLE = 5V 70 200

µA

TJ = 25°C 1.4 1.8

Saturation Voltage VSAT ILOAD = 3A (Note 4) -40°C ≤ TJ ≤ 125°C 2.0 V

TJ = 25°C 50 100

Feedback Bias Current IFB VOUT = 5V

(ADJ version only) -40°C ≤ TJ ≤ 125°C 500

nA

Duty Cycle (ON) DC (Note 5) 93 98 %

TJ = 25°C 4.2 7 8.8

Current Limit ILIMIT (Note 2, 4) -40°C ≤ TJ ≤ 125°C 3.5 7.2 9 A

VOUT = 0V 0.3 2

Output Leakage Current ILEAK (Note 3) VOUT = -1V 9 20 mA

TJ = 25°C 2.2 1.4

VIH V

OUT = 0V -40°C ≤TJ ≤125°C 2.4

TJ = 25°C 1.2 1.0

ENABLE Threshold Voltage

VIL VOUT = Normal

Output Voltage -40°C ≤ TJ ≤ 125°C 0.8

V

IIH ENABLE = 5V 12 30

ENABLE Input Current IIL ENABLE = 0V 0 10

µA

AM C DOC. #: AMC2576_B AMC2576

November 2002

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Note 1: External components such as the catch diode, inductor, input and output capacitors can affect switching

regulator system performance. Refer to Application Information for details.

Note 2: The oscillator frequency reduces to appro ximately 11kHz in the event of fault conditions, such as output

short or overload. And the regulated output voltage will drop approximately 40% from the nominal output

voltage. This self-protection feature lowers the average power dissipation by lowering the minimum duty

cycle from 5% down to approximately 2%.

Note 3: For these parameters, FB is removed from VOUT and connected to +12V to force the output transistor OFF.

Note 4: VOUT pin sourcing current. No diode, inductor or capacitor connect to VOUT.

Note 5: FB is removed from VOUT and connected to 0V.

AM C DOC. #: AMC2576_B AMC2576

November 2002

Copyright  2002, ADD Microtech Corp. 6 www.addmtek.com

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CHARACTERIZATION CURVES

Test circuits of Figure 1 and 2, TJ =25°C, unless otherwise specified.

7.00

7.20

7.40

7.60

7.80

8.00

8.20

8.40

8.60

-40-200 20406080100 120

TJ (°C)

Current Limit (A)

Current limit vs. temperature

VIN = 25V

0.00

0.30

0.60

0.90

1.20

1.50

1.80

2.10

-40 -20 0 20 40 60 80 100 120

Dropout voltage vs. temperature

TJ (°C)

Dropout Voltage (V)

ILOAD=0. 5A

ILOAD=3A

0

20

40

60

80

100

120

140

160

180

-40 -20 0 20 40 60 80 100 120

TJ (°C)

Standby current vs. temperature

Standby current (µA)

VIN =12V

VIN =40V

4.80

4.82

4.84

4.86

4.88

4.90

4.92

4.94

4.96

4.98

5.00

5.02

5.04

5.06

5.08

5.10

0 5 10 15 20 25 30 35 40

Line r egulation

VIN(V)

VOUT(V)

ILOAD=0.5A

ILOAD=3A

VOUT=5V

Output voltage vs. tempe rature

4.90

4.92

4.94

4.96

4.98

5.00

-40-20 0 20406080100 120

VOUT(V)

TJ (°C)

VIN = 12V, VOUT = 5V

ILOAD = 0.5A

0.0

5.0

10.0

15.0

20.0

25.0

30.0

0 10203040

Quiescent current vs. input voltage

Input Voltage(V)

Quiescent Current (mA)

ILOAD=200mA

ILOAD=3A

VOUT = 5V

AM C DOC. #: AMC2576_B AMC2576

November 2002

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CHARACTERIZATION CURVES (continued)

Test circuits of Figure 1 and 2, TJ =25°C, unless otherwise specified.

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

00.511.522.53

Saturation voltage vs. load current

ILOAD (A)

Saturation voltage (V)

TJ = 25°C

TJ =125°C

Load transient response

VOUT

0.5A

3A

5V

Time:100µs/ Div

1A/ Div 100mV/ Div

ILOAD

AM C DOC. #: AMC2576_B AMC2576

November 2002

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Application Information

Input Capacitors (CIN)

It is required that VIN must be bypassed with at least a 100µF electrolytic capacitor for stability. Also, it is strongly

recommended the capacitor’s leads must be dept short, and located near the regulator as possible.

For low operating temperature range, for example, below -25°C, the input capacitor value may need to be larger. T his

is due to the reason that the capacitance value of electrolytic capacitors decreases and the ESR increases with lower

temperatures and age. Paralleling a ceramic or solid tantalum capacitor will increase the regulator stability at cold

temperatures.

Output Capa cit ors (COUT)

An output capacitor is also required to filter the output voltage and is needed for loop stability. The capacitor should

be located near the AMC2576 using short PC board traces. Low ESR types capacitors are recommended for low

output ripple voltage and good stability. Generally, low value or low voltage (less than 12V) electrolytic capacitors

usually have higher ESR numbers. For example, the lower capacitor values (220µF–1000µF) will yield typically 50

mV to 150 mV of output ripple voltage, while larger-value capacitors will reduce the ripple to approximately 20 mV

to 50 mV.

The amount of output ripple voltage is primarily a function of the ESR (Equivalent Series Resistance) of the output

capacitor and the amplitude of the inductor ripple current (∆IIND).

Output Ripple Voltage = (∆IIND) × (ESR of COUT)

Some capacitors called “high-frequency,” “low-inductance,” or “low-ESR.” are recommended to use to further

reduce the output ripple voltage to 10 mV or 20 mV. However, very low ESR capacitors, such as Tantalum capacitors,

should be carefully evaluated.

Catch Diode

This diode is req uired to p r ovide a return path for the inductor current when the switch is off. It should be located

close to the AMC2576 using short leads and short printed circuit traces as possible.

To satisfy the need of fast switching speed and low forward voltage drop, Schottky diodes are widely used to provide

the best efficiency, especially in low output voltage switching regulators (less than 5V). B esides, fast-Recovery,

high-efficiency, or ultra-fast recovery diodes are also suitable. But some types with an abrupt turn-off characteristic

may cause instability and EMI problems. A fast-recovery diode with soft recovery characteristics is a better choice.

AM C DOC. #: AMC2576_B AMC2576

November 2002

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Application Information (contd.)

Output Volt age Ripple and Transients

The output ripple voltage is due mainly to the inductor sawtooth ripple current multiplied by the ESR of the output

capacitor.

The output voltage of a switching power supply will contain a sawtooth ripple voltage at the switcher frequency,

typically about 1% of the output voltage, and may also contain short voltage spikes at the peaks of the sawtooth

waveform.

Due to the fast switching action, and the parasitic inductance of the output filter capacitor, there is voltage spikes

presenting at the peaks of the sawtooth waveform. Cautions must be taken for stray capacitance, wiring inductance,

and even the scope probes used for transients evaluation. To minimize these voltage spikes, shortening the lead length

and PCB traces is always the first thought. Further more, an ad ditional small LC filter (20µH & 100µF) (as shown in

Figure 3) will possibly provide a 10 X reduction in output ripple voltage and transients.

Inductor Selection

The AMC2576 can be used for either continuous or discontinuous modes of operation. Each mode has distinctively

different operating characteristics, which can affect the regulator performance and requirements.

With relatively heavy load currents, the circuit operates in the continuous mode (inductor current always flowing), but

under light load conditions, the circuit will be forced to the discontinuous mode (inductor current falls to zero for a

period of time). For light loads (less than approximately 300 mA) it may be desirable to operate the regulator in the

discontinuous mode, primarily because of the lower inductor values required for the discontinuous mode.

Inductors are available in different styles such as pot core, toroid, E-frame, bobbin core, et., as well as different core

materials, such as ferrites and powdered iron. The least expensive, the bobbin core type, consists of wire wrapped on

a ferrite rod core. This type of construction makes for an inexpensive inductor, but since the magnetic flux is not

completely contained within the core, it generates more electromagnetic interference (EMI). This EMI can cause

problems in sensitive circuits, or can give incorrect scope readings because of induced voltages in the scope probe.

An inductor should not be operated beyond its maximum rated current because it may saturate. When an inductor

begins to saturate, the inductance decreases rapidly and the inductor begins to look mainly resistive (the DC

resistance of the winding). This will cause the switch current to rise very rapidly. Different inductor types have

different saturation characteristics, and this should be well considered when selecting as inductor.

COUT

1000µF

AMC2576-ADJ

OUTPUT

L1

100

µ

H

5

2

4

VIN VOUT

FB

GND

CIN

100µF

7V – 40V

DC INPUT

R2

50K

R1

1.21K

3ENABLE

Figure 3. LC Filter for Low Output Ripple

1L2

20

µ

H

C1

100µF

AM C DOC. #: AMC2576_B AMC2576

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Application Information (contd.)

Feedback Connection

For fi xed output volt age versi on, the FB (feedbac k) pin must be connected to VOUT. For the adjustable version, it is

important to place the output voltage ratio resistors near AMC2576 as possible in order to minimize the noise

introduction.

ENABLE

It is required that the ENABLE must not b e left open. For normal operation, connect this pin to a “LOW” voltage

(typically, below 1.6V). On the other hand, for standby mode, connect this pin with a “HIGH” voltage. This pin can

be safely pulled up to +VIN without a resistor in series with it.

Grounding

To maintain output voltage stability, the power ground connections must be low-impedance. For the 5-lead TO-220

and TO-263 style package, both the tab and pin 3 are ground and either connection may be used.

Heat Sink and Thermal Consideration

Although the AM C2576 requires only a small heat sink for most cases, the following thermal consideration is

important for all operation. With the package thermal resistances θJA and θJC, total power dissipation can be estimated

as follows:

PD = (VIN × IQ)+(VOUT / VIN)(ILOAD × VSAT);

When no heat sink is used, the junction temperature rise can be determined by the following:

∆TJ = PD × θJA;

With the ambient temperature, the actual junction temperature will be:

TJ = ∆TJ +TA ;

If the actual operating junction temperature is out of the safe operating junction temperature (typically 125°C), then a

heat sink is required. When using a heat sink, the junction temperature rise will be reduced by the following:

∆TJ = PD × (θJC + θinterface + θHeat sink);

As one can see from the above, it is important to choose an heat sink with adequate size and thermal resistance, such

that to maintain the regulator’s junction temperature below the maximum operating temperature.

AM C DOC. #: AMC2576_B AMC2576

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5-Pin Plastic TO-220 (P)

INCHES MILLIMETERS

MIN TYP MAX MIN TYP MAX

A 0.560 - 0.650 14.23 - 16.51

B 0.380 - 0.420 9.66 - 10.66

C 0.140 - 0.190 3.56 - 4.82

D 0.018 - 0.035 0.46 - 0.89

F 0.140 - 0.160 3.56 - 4.06

G 0.134 - - 3.40 - -

J 0.012 - 0.045 0.31 - 1.14

K 0.500 - 0.580 12.70 - 14.73

N 0.268 TYP 6.80 TYP

R 0.080 - 0.115 2.04 - 2.92

S 0.045 - 0.055 1.14 - 1.39

T 0.230 - 0.270 5.85 - 6.85

K

D

G

NRJ

B

T

F

C

S

A

5-Pin Surface Mount TO-263 (DD)

INCHES MILLIMETERS

MIN TYP MAX MIN TYP MAX

A 0.395 - 0.420 10.03 - 10.67

B 0.325 - 0.361 8.25 - 9.17

C 0.171 - 0.181 4.34 - 4.59

D 0.045 - 0.055 1.14 - 1.40

E 0.013 - 0.017 0.330 - 0.432

F 0.029 - 0.035 0.737 - 0.889

G 0.062 - 0.072 1.57 - 1.83

I - - 0.065 - - 1.65

K 0.575 0.635 14.60 16.13

L 0.090 0.110 2.29 2.79

M 7° 7°

N 3° 3°

FE

G

B

I

A

M

K

D

C

N

L

AM C DOC. #: AMC2576_B AMC2576

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5-Pin Plastic TO-220B (PB)

INCHES MILLIMETERS

MIN TYP MAX MIN TYP MAX

A 0.380 0.401 0.420 9.65 10.20 10.65

B 0.248 6.30

c 0.348 0.358 0.368 8.85 9.10 9.35

c1 0.167 4.25

d1 0.138 3.50

d2 0.154 3.90

d3 0.213 5.40

e1 0.134 3.40

e2 0.268 6.80

e3 0.032 0.81

f 0.151 3.84

f1 0.039 1.00

G 0.048 0.05 0.052 1.22 1.27 1.32

H 0.996 25.30

I 0.175 0.180 0.185 4.44 4.57 4.70

J 0.965 24.50

K 0.105 2.67

L 0.164 0.173 0.182 4.17 4.40 4.63

M 0.05 1.27

N 0.013 0.015 0.025 0.33 0.381 0.63

O 0.322 0.331 0.340 8.17 8.40 8.63

z1 7°

7°

z2 7°

7°

z3 7°

7°

z4 5°

5°

Z5 5°

5°

d3

z2

z3

d1

HJ

O

d2

e1

e2

K

L

A

B

c

c1

z1

z4

G

I

M

f

f1

e3

z5

N

AM C DOC. #: AMC2576_B AMC2576

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IMPORTANT NOTICE

ADD Microtech (ADDM) reserves the right to make changes to its products or to discontinue any integrated circuit

product or service without notice, and advises its custo mers to o btain the latest version of relevant infor mation to verify,

before placing orders, that the information being relied on is current.

A few applications using integrated circuit products may involve potential risks of death, personal injury, or severe

property or environmental damage. ADDM integrated circuit products are not designed, intended, authorized, or

warranted to be suitable for use in life-support applications, devices or systems or other critical applications. Use of

ADDM products in such applications is understood to be fully at the risk of the customer. In order to minimize risks

associated with the customer’s applications, the customer should provide adequate design and operating safeguards.

ADDM assumes to no liability to customer product design or application support. ADDM warrants the performance of

its products to the specifications applicable at the time of sale.

U.S. Asia Pacific region

ADD Microtech Inc.

492 Altamont Drive

Milpitas, CA 95035

ADD Microtech Co rp

3F, 132, Sec. 4, Chung Hsiao E. Rd .,

Taipei, Taiwan

TEL: (408) 9410420 TEL: 2-27760166

F AX: (408) 9410864 F AX: 2-27764208