ame5258a AME, Inc., ame5258a Datasheet - Page 10

• Manufacturer Part Number: ame5258a
• Description: Synchronous Buck Converter
• Manufacturer: AME, Inc.

Output Voltage Programming
according to the following equation :
much heat due to its high efficiency. But, in applications
where the AME5258A is running at high ambient tem-
perature with low supply voltage and high duty cycles,
such as in dropout, the heat dissipated may exceed the
maximum junction temperature of the part. If the junction
temperature reaches approximately 160
switches will be turned off and the SW node will become
high impedance. To avoid the AME5258A from exceed-
ing the maximum junction temperature, the user will need
to do some thermal analysis. The goal of the thermal
analysis is to determine whether the power dissipated
exceeds the maximum junction temperature of the part.
The temperature rise is given by:
10
Thermal Considerations
to the ambient temperature.
AME5258A
V
vider allows the FB pin to sense a fraction of the output
voltage as shown in Figure 3.
JA
The output voltage is set by an external resistive divider
In most applications the AME5258A does not dissipate
OUT
Where PD is the power dissipated by the regulator and
Where VREF equals to 0.6V typical. The resistive di-
is the thermal resistance from the junction of the die
T
Figure 3: Setting the AME5258A Output Voltage
R
(
V
AME5258A
PD
REF
AME
)(
GND
JA
FB
1 (
)
0.6V
R
R
1
2
)
V
OUT
R2
R1
O
5.5V
C, both power
2.7V to 5.5V
3.3V to 5.5V
2.5V to 5.5V
C
4.7 F
CER
4.7 F
CER
4.7 F
CER
C
Synchronous Buck Converter
C
OUT
V
OUT
V
OUT
V
IN
IN
IN
Figure 5: 1.5V Step-Down Regulator
Figure 4: 1.2V Step-Down Regulator
Figure 6: 2.5V Step-Down Regulator
IN
EN
IN
EN
EN
IN
AME5258A
AME5258A
AME5258A
GND
GND
GND
SW
SW
SW
FB
FB
FB
1.5MHz, 800mA
316K
316K
604K
2.2 H
2.2 H
2.2 H
475K
604K
22pF
22pF
22pF
1M
Rev.A.01
V
V
2.5V
V
1.2V
1.5V
OUT
CER
OUT
CER
C
10 F
OUT
CER
C
10 F
C
10 F
OUT
OUT
OUT