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AE2596
Specification
SIMPLE SWITCHER POWER CONVERTER AE2596
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u u u u u u u u u u u
Features
3.3V, 5V, 12V, and adjustable output versions Adjustable version output voltage range,1.2V to 37V TO-220 and TO-263 packages Output load current 3A Input voltage range up to 40V Requires only 4 external components 150 kHz fixed frequency internal oscillator TTL shutdown capability Low power standby mode, IQ typically 80 A High efficiency Thermal shutdown and current limit protection
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General Description
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Application Simple high-efficiency step-down (buck) regulator On-card switching regulators Positive to negative converter
The AE2596 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down(buck) switching regulator, capable of driving a 3A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5V, 12V, and an adjustable output version. Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation, and a fixed frequency oscillator. The AE2596 series operates at a switching frequency of 150 kHz thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. Available in a standard 5-lead TO-220 package with several different lead bend options, and a 5-lead TO-263 surface mount package. Other features include a guaranteed4% tolerance on output voltage under specified input voltage and output load conditions, and15% on the oscillator frequency. External shutdown is included, featuring typically 80 A standby current. Selfprotection features include a two stage frequency reducing current limit for the output switch and an over temperature shutdown for complete protection under fault conditions.
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Pin Configuration
Pin No. Symbol Parameter
1 VIN DC Input
2 Output DC Output
3 GND Ground
4 Feedback Feedback signal
5 Standby control
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AE2596
Specification
AE1501
AE1501
AE1501
12345
12345
5-LeadTO-220(B) n Block Diagram
12345
5-Lead TO-220(T) 5-Lead TO-263(S)
ON/OFF 5 1
Vin GND OUTPUT
CURRENT SOURCE BIAS
1.235V REFERENCE
2.5V REGULATOR
START UP
CURRENT LIMIT
FEEDBACK
2.5V
4
R2
GM AMP COMP
LATCH DRIVER
R1=2.5K
3.3V, R2=4.2K 5V, R2=7.6K 12V, R2=21.8K ADJ, R2=0, R1=OPEN
RESET
150KHz OSC THERMAL LIMIT
2 3
2
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AE2596
Rating 45 -0.3 -0.3 -65 -40 4.75 25 25 150 125 40
Specification
Unit V V V -ae ae ae V
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Absolute Aaximum Ratings(note1) Parameter Maximum Supply Voltage
ON/OFF Pin Input Voltage
Feedback Pin Voltage Power Dissipation Storage Temperature Range Maximum Junction Temperature Conditions n Temperature Range Supply Voltage Electrical Characteristics VO=3.3V Symbol Parameter Output Voltage Efficiency Output Voltage Efficiency Conditions 5VU VINU 40V 0.2AU ILOADU 3A VIN=12V ILOAD=3A 7VU VINU 40V 0.2AU ILOADU 3A VIN=12V ILOAD=3A 15VU VINU 40V 0.2AU ILOADU 3A VIN=25V ILOAD=3A Min (Note 4)
Internally limited 150
Typ (Note 3)
Max (Note4 )
Units
VOUT |C VO=5V VOUT |C VO=12V VOUT
3.18 --
3.30 72
3.40 --
V %
4.80 --
5.0 79
5.15 --
V %
Output Voltage |C Efficiency Vout is adjustable
11.65 --
12.0 88
12.35 ---
V %
VFB
Feedback Voltage
4.5VU VINU 40V 0.2AU ILOADU 3A VOUT programmed for 3V.
1.195
1.230
1.255
V
|C
Efficiency
VIN=12V VOUT=3V ILOAD=3A
--
71
--
%
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AE2596
Specification
n All Output Voltage Versions Electrical Characteristics(otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version and VIN = 24V for the 12V version.ILOAD = 500 mA) Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may AE2596Symbol Parameter Feedback Bias Current Oscillator Frequency VSAT Saturation Voltage Max Duty Cycle Min Duty Cycle Current Limit Output Short Current Output Leakage Current Quiescent Current Standby Quiescent Current Conditions Adjustable Version Only, VFB = 1.3V (Note 6) IOUT=3A(Notes 7, 8) ON (Note 8) OFF(Note 9) Peak Current (Notes 7, 8) RLOAD=0 Output = 0V (Notes 7, 9) Output =-1V (Notes 10) (Note 9)
ON /OFF pin = 5V
XX Max (Note) 60 173 1.60 --5.50 6.40 60 30 12 180 -----ae ae ae ae Units
Min (Note 4) -135 ---4.0 5.20 ----------
Typ (Note 3) 10 150 1.36 100 0 4.80 5.50 -4 7.60 80 2 50 50 30 20
Ib fO VSAT DC ICL ISC
nA KHz V % % A A |I A mA mA |I A ae /W /W /W /W /W
IL
IQ ISTBY |E |E |E |E |E
JC JA JA JA JA
(OFF) (Note 10) TO-220 or TO-263 TO-220
Thermal Resistance
TO-263 TO-263 TO-263
CONTROL
ON /OFF Pin
Logic Input VIH VIL IH IL Threshold Voltage Low (Regulator on) High(Regulator off) VLOGIC=2.5V (Regulator OFF) VLOGIC=0.5V (Regulator ON)
-2.0 ----
1.3 --4 0.02
--0.8 15 2
V V V |I A |I A
ON /OFF Pin Input
Current
occur. Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into
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AE2596
and represent the most likely norm.
Specification
each pin. Note 3: Typical numbers are at 25ae
Note4: All limits guaranteed at room temperature (standard type face) and at t emperature extremes (bold type face). All room temperature limits are 100% production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Note5: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator system performance. Note6: The switching frequency is reduced when the second stage current limit is activated. Note7: No diode, inductor or capacitor connected to output pin. Note8: Feedback pin removed from output and connected to 0V to force the output transistor switch ON. Note9: Feedback pin removed from output and connected to 12V for the 3.3V, 5V, and the ADJ. version, and 15V for the 12V version, to force the output transistor switch OFF. Note10: VIN = 40V. Note11: Junction to ambient thermal resistance (no external heat sink) for the TO-220 package mounted vertically, with the leads soldered to a printed circuit board with (1 oz.)copper area of approximately 1 in2.
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AE2596
Specification
n
Typical Performance Characteristics
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AE2596
Specification
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Testing Circuit Fixed Output Voltage Versions
4
+Vin
Feedback Output
AE2596
FIXED OUTPUT
L1
OUTPUT
DC INPUT
1 Cin
2
3
GND
5
ON/OFF
D1
Cout
L O A D
CIN --470 F, 50V, Aluminum Electrolytic Nichicon "PL Series" COUT --220 F, 25V Aluminum Electrolytic, Nichicon "PL Series" D1 --5A, 40V Schottky Rectifier, 1N5825 L1 --68 H, L38 Note: Keep Feedback wiring away from inductor flux and heavy line must be kept short and use ground plane construction or best results. Adjustable Output Voltage Versions
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AE2596
Cff
Specification
R1 1K
+Vin
R2
4 Feedback
AE2596
ADJ Output
L1
OUTPUT
1
2 5 ON/OFF
Cout L
DC INPUT
Cin 3 GND
D1
O A D
where VREF = 1.23V, VOUT=VREF(1 +
R2 ) R1
R2=R1(
VOUT VREF
1)
Select R1 to be approximately 1 k , use a 1% resistor for best stability. CIN --470 F, 50V, Aluminum Electrolytic Nichicon "PL Series" COUT --220 F, 35V Aluminum Electrolytic, Nichicon "PL Series" D1 --5A, 40V Schottky Rectifier, 1N5825 L1 --68 H, L38 R1 --1 k , 1% CFF --See Application Information Section Note: Keep Feedback wiring away from inductor flux and heavy line must be kept short and use ground plane construction or best results. n Typical Application circuit
DC12V
+Vin 1 Cin 680uF
AE1501 AE2596 AE2596 5.0
Feedback 4 Output 2
L1 33uH D1 IN5824
5.0V
3A Load
5 3 ON/OFF GND
Cout 220uF
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Pin Functions +VIN This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching currents
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AE2596
Specification
needed by the regulator.
Ground Circuit ground. Output Internal switch. The voltage at this pin switches between (+VIN - VSAT) and approximately-0.5V,with a duty cycle of approximately VOUT / VIN. To minimize coupling to sensitive circuitry, the PC board copper area connected to this pin should be kept a minimum. Feedback Senses the regulated output voltage to complete the feedback loop. Allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply current to approximately 150uA. Pulling this pin below a threshold voltage of approximately 1.3V turns the regulator on, and pulling this pin above 1.3V (up to a maximum of 25V) shuts the regulator down. If this shutdown feature is not needed, the ON /OFF pin can be wired to the ground pin or it can be left open, in either case the regulator will be in the ON condition. n External Components INPUT CAPACITOR CIN --A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground pin . It must be located near the regulator using short leads. This capacitor prevents large voltage transients from appearing at the input, and provides the instantaneous current needed each time the switch turns on.Selecting an input capacitor requires consulting the manufa- cturers data sheet for maximum allowable RMS ripple current. For a maximum ambient temperature of 40C, a general guideline would be to select a capacitor with a ripple current rating of approximately 50% of the DC load current. For ambient temperatures up to 70C, a current rating of 75% of the DC load current would be a good choice for a conservative design. The capacitor voltage rating must be at least 1.25 times greater than the maximum input voltage,and often a much higher voltage capacitor is needed to satisfy the RMS current requirements. FEEDFORWARD CAPACITOR (Adjustable Output Voltage Version) CFF ----A feed forward Capacitor CFF, shown across R2 in Figure1 is used when the ouput voltage is greater than 10V or when COUT has a very low ESR. This capacitor adds lead compensation to the feedback loop and increases the phase margin for better loop stability. OUTPUT CAPACITOR COUT ---An output capacitor is required to filter the output and provide regulator loop stability. Low impedance or low ESR Electrolytic or solid tantalum capacitors designed for switching regulator applications must be used. When selecting an output capacitor, the important capacitor parameters are; the 100 kHz Equivalent Series esistance (ESR), the RMS ripple current rating, voltage rating, and capacitance value. For the output capacitor, the ESR value is the most important parameter.The output capacitor requires an ESR value that has an upper and lower limit. For low output ripple voltage, a low ESR value is needed. This value is determined by the maximum allowable output ripple voltage, typically 1% to 2% of the output voltage. But if the selected capacitor's ESR is extremely low, there is a possibility of an unstable feedback loop, resulting in an oscillation at the output. CATCH DIODE D----Buck regulators require a diode to provide a return path for the inductor current when the switch turns off. This must be a fast diode and must be located close to the
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AE2596
Specification
AE2596 using short leads and short printed circuit traces. Because of their very fast switching speed and low forwardvoltage drop, Schottky diodes provide the best performance, especially in low output voltage applications (5V and lower).Ultrafast recovery, or High-Efficiency rectifiers are also a good cho- ice, but some types with an abrupt turnoff characteristic may cause instability or EMI problems. INDUCTOR SELECTION L----All switching regulators have two basic modes of operation; continuous and discontinuous. The difference between the two types relates to the inductor current, whether it is flowing continuously, or if it drops to zero for a period of time in the normal switching cycle. Each mode has distinctively different operating characteristics, which can affect the regulators performance and requirements. Most switcher designs will operate in the discontinuous mode when the load current is low.The AE2596 (or any of the Simple Switcher family) can beused for both continuous or discontinuous modes of operation.There is a formula for general applications: L=(5 10) V O
300 I O
(1- V O )mH
V IN
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AE2596
Specification
n
Package Information
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AE2596
Specification
12
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D
A
AE2596
Specification
TO-220(T)
c1
F
|
A2
E1
R
AE1501
L1
A1
E
L2
c
e
e1
Dimensions In Millimeters Symbol A A1 A2 b c c1 D E E1 e e1 F L1 L2 R 6.700 2.590 28.700 13.36 0.950 3.790 Min 4.470 2.520 1.170 0.710 0.310 1.170 10.010 8.900 12.460 1.700TYP 6.900 2.890 29.100 13.76 1.050 3.890 Max 4.670 2.820 1.370 0.910 0.530 1.370 10.310 9.300 12.860
Dimensions In Inches Min 0.176 0.099 0.046 0.028 0.012 0.046 0.394 0.350 0.491 0.220TYP 0.264 0.102 1.130 0.526 0.037 0.149 0.272 0.114 1.146 0.542 0.041 0.153 Max 0.184 0.111 0.054 0.036 0.021 0.054 0.406 0.366 0.506
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