A5974ADTR STMicroelectronics, A5974ADTR Datasheet - Page 25

• Manufacturer Part Number: A5974ADTR
• Description: IC REG SW STEP-DOWN 2A 8SOIC
• Manufacturer: STMicroelectronics
• Series: -r
• Type: Step-Down (Buck), PWMr

Specifications of A5974ADTR

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.235 V ~ 35 V
• Current - Output: 2A
• Frequency - Switching: 500kHz
• Voltage - Input: 4 V ~ 36 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width) Exposed Pad
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-11423-2

A5974AD
●
Very good, small tantalum capacitors with very low ESR are becoming more available.
However, they can occasionally burn if subjected to very high current during charge
Therefore, it is better to avoid this type of capacitor for the input filter of the device. They can,
however, be subjected to high surge current when connected to the power supply
Table 6.
●
The output capacitor is very important to meet the output voltage ripple requirement.
Using a small inductor value is useful to reduce the size of the choke but it increases the
current ripple. So, to reduce the output voltage ripple, a low ESR capacitor is required.
Nevertheless, the ESR of the output capacitor introduces a zero in the open loop gain,
which helps to increase the phase margin of the system. If the zero goes to a very high
frequency, its effect is negligible. For this reason, ceramic capacitors and very low ESR
capacitors in general should be avoided.
Tantalum and electrolytic capacitors are usually a good choice for this purpose. A list of
some tantalum capacitor manufacturers is provided in
Table 7.
1. POSCAP capacitors have some characteristics which are very similar to tantalum.
●
The inductor value is very important as it fixes the ripple current flowing through the output
capacitor. The ripple current is usually fixed at 20 - 40% of I
I
Equation 20
Omax
Sanyo POSCAP
AVX
KEMET
Sprague
Manufacturer
TAIYO YUDEN
Tantalum capacitors:
Manufacturer
Output capacitor
Inductor
= 3 A. The approximate inductor value is obtained using the following formula:
MURATA
List of ceramic capacitors for the A5974AD
Output capacitor selection
(1)
T494/5
Series
595D
GRM42-2 X7R 475K 50
TPS
TAE
TV
UMK325BJ106MM-T
Doc ID 018762 Rev 1
Series
L
=
(
---------------------------------- T
V
Cap value (µF)
IN
100 to 470
100 to 470
220 to 390
47 to 680
68 to 330
–
ΔI
V
OUT
)
⋅
Capacitor value (µ)
ON
Table
Rated voltage (V)
4.7
10
Omax
2.5 to 10
7.
4 to 6.3
4 to 35
4 to 20
4 to 20
, which is 0.6 - 1.2 A with
Application information
Rated voltage (V)
160 to 650
ESR (mΩ)
50 to 200
30 to 200
25 to 35
25 to 40
50
50
25/49