LM2594M-ADJ/NOPB National Semiconductor, LM2594M-ADJ/NOPB Datasheet - Page 14

• Manufacturer Part Number: LM2594M-ADJ/NOPB
• Description: IC REG SIMPLE SWITCHER 8-SOIC
• Manufacturer: National Semiconductor
• Series: SIMPLE SWITCHER®r
• Type: Step-Down (Buck)r

Specifications of LM2594M-ADJ/NOPB

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.2 ~ 37 V
• Current - Output: 500mA
• Frequency - Switching: 150kHz
• Voltage - Input: 4.5 ~ 40 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Primary Input Voltage: 60V
• No. Of Outputs: 1
• Output Voltage: 37V
• Output Current: 500mA
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +125°C
• Msl: MSL 1 - Unlimited
• Rohs Compliant: Yes
• Current, Input Bias: 10 nA
• Current, Output: 0.5 A
• Current, Supply: 5 mA
• Frequency, Oscillator: 150 kHz
• Package Type: SOIC
• Regulator Type: Buck (Step-Down)
• Temperature, Operating, Range: -40 to +125 °C
• Voltage, Input: 4.5 to 40 V
• Voltage, Output: 1.2 to 37 V
• Peak Reflow Compatible (260 C): Yes
• Termination Type: SMD
• Filter Terminals: SMD
• Input Voltage: 40V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device
• Other names: *LM2594M-ADJ; LM2594M-ADJ

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LM2594/LM2594HV Series Buck Regulator Design Procedure (Adjustable
Output)
6. Input Capacitor (C
A low ESR aluminum or tantalum bypass capacitor is needed
between the input pin and ground to prevent large voltage
transients from appearing at the input. In addition, the RMS
current rating of the input capacitor should be selected to be
at least
data sheet must be checked to assure that this current rating
is not exceeded. The curve shown in Figure 13 shows typical
RMS current ratings for several different aluminum electro-
lytic capacitor values.
This capacitor should be located close to the IC using short
leads and the voltage rating should be approximately 1.5
times the maximum input voltage.
If solid tantalum input capacitors are used, it is recomended
that they be surge current tested by the manufacturer.
Use caution when using ceramic capacitors for input bypass-
ing, because it may cause severe ringing at the V
For additional information, see section on input capaci-
tors in application information section.
Output
PROCEDURE (Adjustable Output Voltage Version)
Volt-
age
1.2
1 2
1 5
2 4
2 8
(V)
4
6
9
1
⁄
2
the DC load current. The capacitor manufacturers
(Continued)
HFQ Series
Panasonic
220/25
180/25
(µF/V)
82/25
82/25
82/25
82/25
82/50
82/50
IN
)
Through Hole Output Capacitor
FIGURE 3. Output Capacitor and Feedforward Capacitor Selection Table
Nichicon PL
220/25
180/25
120/50
120/50
Series
(µF/V)
82/25
82/25
82/25
82/25
IN
pin.
Feedforward
Capacitor
820 pF
4.7 nF
4.7 nF
3.3 nF
2.2 nF
1.5 nF
1 nF
0
14
6. Input Capacitor (C
The important parameters for the Input capacitor are the in-
put voltage rating and the RMS current rating. With a nominal
input voltage of 28V, an aluminum electrolytic aluminum elec-
trolytic capacitor with a voltage rating greater than 42V (1.5 x
V
voltage rating is 50V, a 50V capacitor should be used. The
capacitor voltage rating of (1.5 x V
line, and can be modified somewhat if desired.
The RMS current rating requirement for the input capacitor of
a buck regulator is approximately
this example, with a 400 mA load, a capacitor with a RMS
current rating of at least 200 mA is needed.
The curves shown in Figure 13 can be used to select an ap-
propriate input capacitor. From the curves, locate the 50V
line and note which capacitor values have RMS current rat-
ings greater than 200 mA. A 47 µF/50V low ESR electrolytic
capacitor capacitor is needed.
For a through hole design, a 47 µF/50V electrolytic capacitor
(Panasonic HFQ series or Nichicon PL series or equivalent)
would be adequate. Other types or other manufacturers ca-
pacitors can be used provided the RMS ripple current ratings
are adequate.
For surface mount designs, solid tantalum capacitors are
recommended. The TPS series available from AVX, and the
593D series from Sprague are both surge current tested.
To further simplify the buck regulator design procedure, Na-
tional Semiconductor is making available computer design
software to be used with the Simple Switcher line ot switch-
ing regulators. Switchers Made Simple (version 4.1 or later)
is available from National’s web site, www.national.com.
IN
) would be needed. Since the the next higher capacitor
EXAMPLE (Adjustable Output Voltage Version)
AVX TPS
Series
220/10
100/10
100/10
100/16
100/16
(µF/V)
68/20
10/35
10/35
Surface Mount Output Capacitor
IN
595D Series
)
Sprague
220/10
120/10
120/10
100/16
100/16
100/20
(µF/V)
15/35
15/35
IN
1
⁄
) is a conservative guide-
2
the DC load current. In
Feedforward
Capacitor
220 pF
220 pF
4.7 nF
4.7 nF
3.3 nF
2.2 nF
1.5 nF
0