AMS2596

The AMS2596 Series are step-down switching regulators with all required active functions. It is capable of driving 2.5A load with excellent line and load regulations. These devices are available in fixed output voltages of 3.3V, 5V, 12V and an adjustable output version.

The AMS2596 series offers a high-efficiency replacement for popular three-terminal linear regulators. Also it requires a minimum number of external components. It substantially not only reduces the area of board size but also the size of heat sink, and in some cases no heat sink is required. The ±4% tolerance on output voltage within specified input voltages and output load conditions is guaranteed. Also, the oscillator frequency accuracy is within ±15%. External shutdown is included. Featuring 80µA (typical) standby current. The output switch includes cycle-by-cycle current limiting, as well as thermal shutdown for full protection under fault conditions.

This series are offered in 5-pin TO-263, TO-220 package.

FEATURES

󰂋 3.3V, 5V, 12Vand adjustable versions 󰂋 Wide input voltage range, up to 40V󰂋 Internal oscillator of 150KHz fixed frequency 󰂋 Guaranteed 2.5A output current

󰂋 Wide adjust version output voltage range

from 1.23V to 37V ±4% max. at over line and load conditions

󰂋 Low standby current, typ. 80µA, at shutdown

mode

󰂋 Requires only 4 external components 󰂋

Thermal shutdown and current limit protection

APPLICATIONS

󰂄 LCD Monitors.

󰂄 ADD-ON Cards Switching Regulators 󰂄 High Efficiency Step-Down Regulators 󰂄 Efficient Pre-regulator for Linear Regulators 󰂄 Positive to Negative converter (Buck-Boost)

Block Diagram

DC Input+Vin1InternalRegulatorEnable5Enable4FeedBackR2+R11KFixed GainError amp.Comparator2.5Amp.DriverSwitchL1+CoutD1LOAD-+-2ThermalShutdown3CurrentLimitedOutput1.23VBand-GapReference150KHzOscillatorReset1Advanced Monolithic Systems http://www.ams-semitech.comOrdering Information

Part No.

AMS2596T-XX AMS2596T-ADJ AMS2596S-ADJ AMS2596S-XX

Operating Temp.

(Ambient) -20 ~ +85℃

AMS2596Package TO-220-5L TO-263-5L

Note: Where XX denotes voltage option, Available are 12V, 5V and 3.3V. Leave blank for adjustable version. Contact factory for additional voltage options.

Pin assignment

1. Input 2. Output 3. Ground 4. Feedback

TO-220 TO-263

5. Enable

Absolute Maximum Ratings

Input voltage Power Dissipation

Operating Junction Temperature RangeStorage Temperature Range Lead Soldering Temperature (260℃)

TO-220-5L / TO-263-5L

Package

10 S Vin

+45

V

ENABLE Pin Input Voltage Vin (operate)-0.3V ≤ V ≤ Vin V

PD Internal Limited W TJ TSTG

-40 ~ +150 -65 ~ +150

℃ ℃

2Advanced Monolithic Systems http://www.ams-semitech.com AMS2596Electrical Characteristics

Vin = 12V, IL= 500mA, Ta = 25oC unless otherwise specified.

Parameter Conditions Min Typ Max Unit AMS2596-3.3V

Output Voltage (Note 1) Vin=12V, IL=0.5A (Figure 1) Output Voltage (Note 1) 0.5A ≤IL ≤2.5A, 6V ≤Vin ≤45V (Figure 1)

0.98|Vo| 0.96|Vo|

3.3

1.02|Vo| 1.04|Vo|

V

Efficiency Vin=12V, IL=2.5A -- 75 -- % AMS2596-5V

Output Voltage (Note 1) Vin=12V, IL=0.5A(Figure 1) Output Voltage (Note 1) 0.5A ≤IL ≤2.5A, 8V ≤Vin ≤45V (Figure 1)

0.98|Vo| 0.96|Vo|

5.0

1.02|Vo| 1.04|Vo|

V

Efficiency Vin=12V, IL=2.5A -- 77 -- % AMS2596-12V

Output Voltage (Note 1) Vin=25V, IL=0.5A (Figure 1) Output Voltage(Note 1)

0.5A ≤IL ≤2.5A, 15V ≤Vin ≤45V (Figure 1)

0.98|Vo| 0.96|Vo|

12

1.02|Vo| 1.04|Vo|

V

Efficiency Vin=15V, IL=2.5A -- 88 -- % AMS2596

Feedback Voltage (Note 1) Feedback Voltage (Note 1)

Vin=12V, Vout=5V,IL=0.5A (Figure 2)

0.5A ≤IL ≤2.5A, 8V ≤Vin ≤45V, Vout=5V (Figure 2)

0.96|Vo|

1.04|Vo|

0.98|Vo|

1.23

1.02|Vo|

V

Efficiency Vin=12V, Vout=5V, IL=2.5A -- 77 -- %

3Advanced Monolithic Systems http://www.ams-semitech.com All Output Voltage Version

(Vin=12V for 5V, 3.3V and Adjustable version, Vin=25V for 12V version, IL= 500mA)

AMS2596Oscillator Frequency (Note 2) 127 150 173 kHz Quiescent Current (Note 3) Standby Current

ENABLE =5V

-- 5 10 mA --

80

250

uA Saturation Voltage (Note 4) ILOAD=2.5A -- 1.2 1.5 V Feedback Bias Current

VOUT=5V (Adj. Version only)

--

10

100

nA

Duty Cycle (Note 5) Operating (ON) 100 -- % Current Limit (Note 2)(Note 4) 3.1 4.0 5.0 A Output Leakage Current (Note 3)

VOUT=0V -- 0.3 2 VOUT=-1V -- 7.5 30 VIH(VOUT=0V)

VIL(VOUT=Normal Output Voltage) IIH (ENABLE =5V) IIH (ENABLE =0V)

2.2 1.4 -- --

1.2

1.0

mA

ENABLE Threshold Voltage V

ENABLE Input Current

-- 12 30 uA

-- 0 10

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

4Advanced Monolithic Systems http://www.ams-semitech.com AMS2596be located close to the AMS2596 using short leads

Application Information

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℃, the input capacitor value may need to be larger. This is due to the reason that the

and short printed circuit traces as possible.

To satisfy the need to 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). Beside, 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 better choice.

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

near the AMS2596 using short PC board traces.

operates in the continuous mode (inductor current

Low ESR types capacitors are recommended for

always flowing). But under light Load conditions,

low output ripple voltage and good stability.

the circuit will be force to the discontinuous mode

Generally, low value or low voltage (less than12V)

(inductor current falls to zero for a period of time).

electrolytic capacitors usually have higher ESR

For light loads (less than approximately 300mA) it

numbers, For example, the lower capacitor

may be desirable to operate the regulator in the

values (220µF - 1000µF) will yield typically 50mV

discontinuous mode, primarily because of the

to 150mV of output ripple voltage, while

lower inductor values required for the

larger-value capacitors will reduce the ripple to

discontinuous mode.

approximately 20mV to 50mV.

Indictors are available in different styles such as pot core, toroid, E-frame, bobbin core, et., as well The amount of output ripple voltage is primarily a

function of the ESR (Equivalent Series as different core materials such as ferrites and Resistance) of the output capacitor and the powdered iron. The least expensive, the bobbin amplitude of the inductor ripple current (△IIND) core type, consists of wire wrapped on a ferrite Output Ripple Voltage = (△IIND) x (ESR of rod core. This type of construction makes for an

inexpensive inductor, but since the magnetic flux COUT) Some capacitors called “high-frequency”,

is not completely contained within the core, it “low-inductance”, or “low-ESR” are recommended

generates more electromagnetic interference to use to further reduce the output ripple voltage

to 10mV or 20mV. However, very low ESR (EMI). This EMI can cause problems in sensitive

circuits, or can give incorrect scope readings capacitors, such as tantalum capacitors, should

because of induced voltage in the scope probe. be carefully evaluated.

An inductor should not be operated beyond its Catch Diode

This diode is required to return path for the maximum rated current because it may saturate.

When an inductor begins to saturate, the inductor current when the switch is off. It should

capacitance value of electrolytic capacitors

decreases and the ESR increases with lower temperatures and ago. Paralleling a ceramic or solid tantalum capacitor will increase the regulator stability at cold temperatures. Output Capacitor

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

Inductor Selection

The AMS2596 can be used for either continuous or

5Advanced Monolithic Systems http://www.ams-semitech.com AMS2596inductance 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.

lead length and PCB traces is always the first thought. Further more, an additional small LC filter (30µH & 100µF) (as shown in Figure 3) will possibly provide a 10X reduction in output ripple voltage and transients.

Heatsink and Thermal Consideration

Although the AMS2596 requires only a small

Feedback Connection

For fixed output voltage version, the FB (feedback) pin must be connected to VOUT. For the adjustable version, it is important to place the output voltage ratio resistors near AMS2596as possible in order to minimize the noise introduction.

heatsink for most cases, the following thermal consideration is important for all operation. With the package thermal resistances Өja and Өjc , total power dissipation can be estimated as follows:

PD= (Vin x Iq) + (Vout / Vin) (Iout x Vsat);

When no heatsink is used, the junction temperature rise can be determined by the following: ∆TJ = PD x Өja

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℃), then a heatsink is required. When using a heatsink, the junction temperature rise will be reduced by the following: ∆Tj= PD x (Өjc + Ө interface + Ө heatsink ); Also one can see from the above, it is important to choose an heatsink with adequate size and thermal resistance, such that to maintain the regulator’s junction temperature below the maximum operating temperature.

Enable Input

It is required that the ENABLE must not be 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 rather connection may be used.

Thermal Characteristics

The output ripple voltage is due mainly to the inductor sawtooth ripple current multiplied by the ESR of the output capacitor. The output ripple voltage of a switching power supply will contain a sawtooth ripple voltage at the switcher frequency, typically about 1% of the output voltages, and may also contain short voltage spokes 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

6Advanced Monolithic Systems http://www.ams-semitech.com Application Circuit

FeedBackL1 AMS2596

VinAMS2591FixedOutputVoltage2Vout3547µHUnregulated+CinGndEnbaleDC Input470µF+Cout1N5824220µFLOAD

Figure 1 Fixed Voltage version

VinAMS259FeedBack1AdjustableL1Voltage2OutputVoutVout3547µHUnregulated+CinGndEnbaleR2DC Input470µF+Cout1N5824220µFLOADR1Vout=1.23×(1+R2/R1)

Figure 2: Adjustable Voltage Version

VinAMS259FeedBack1AdjustableVoltage2OutputL1VoutVoutL23547µH3µHUnregulated+CinGndEnbaleDC Input470µF+CoutR21N5824220µFC1R1180µF

Figure 3: LC filter for Low Output Ripple

7Advanced Monolithic Systems http://www.ams-semitech.comOutput

Package Description

TO-220-5L Mechanical Drawing

DIM

AMS2596TO-220 DIMENSION

INCHES MIN

MAX

0.394 0.4130.128 0.1750.096 0.116 0.010 0.0400.062 0.0720.524 0.5560.176 0.2060.046 0.0541.087 1.1590.086 0.115 0.012 0.0190.326 0.3460.237 0.2560.563 0.603

MAX 10.504.4402.9401.0201.83014.135.2251.37029.442.9250.4778.8006.51015.31

MILLIMETERS MIN

A 10.00B 3.240C 2.440D 0.260E 1.570F 13.31G 4.475H 1.170I 27.60J 2.175K 0.297L 8.280M 6.010N 14.29

TO-263-5L Mechanical Drawing

TO-263 DIMENSION

DIM

MILLIMETERS INCHES

MIN MAX MIN MAX

A 10.22010.260 0.402 0.404 B 14.60015.870 0.575 0.625 C 0.750 0.770 0.030 0.030 D 1.573 1.827 0.062 0.072 E 4.560 4.570 0.179 0.180 F 1.240 1.270 0.049 0.050 G 2.280 2.790 0.090 0.110 H 0.280 0.320 0.011 0.013 I 8.240 8.280 0.324 0.326 J 1.540 1.800 0.060 0.071

8Advanced Monolithic Systems http://www.ams-semitech.com AMS2596Disclaimer:

• AMS reserves the right to make changes to the information herein for the improvement of the design and performance

without further notice! Customers should obtain the latest relevant information before placing orders and should verify that such information is complete and current.

• All semiconductor products malfunction or fail with some probability under special conditions. When using AMS products

in system design or complete machine manufacturing, it is the responsibility of the buyer to comply with the safety standards strictly and take essential measures to avoid situations in which a malfunction or failure of such AMS products could cause loss of body injury or damage to property. • AMS will supply the best possible product for customers!

9Advanced Monolithic Systems http://www.ams-semitech.com