ame5258 AME, Inc., ame5258 Datasheet - Page 10

• Manufacturer Part Number: ame5258
• 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 AME5258 is running at high ambient tempera-
ture with low supply voltage and high duty cycles, such
as in dropout, the heat dissipated may exceed the maxi-
mum junction temperature of the part. If the junction tem-
perature reaches approximately 160
switches will be turned off and the SW node will become
high impedance. To avoid the AME5258 from exceeding
the maximum junction temperature, the user will need to
do some thermal analysis. The goal of the thermal analy-
sis is to determine whether the power dissipated exceeds
the maximum junction temperature of the part. The tem-
perature rise is given by:
10
Thermal Considerations
to the ambient temperature.
AME5258
V
vider allows the FB pin to sense a fraction of the output
voltage as shown in Figure 4.
JA
The output voltage is set by an external resistive divider
In most applications the AME5258 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 4: Setting the AME5258 Output Voltage
R
(
V
PD
AME5258
REF
AME
)(
GND
JA
FB
1 (
)
0.6V
R
R
1
2
)
V
OUT
R2
R1
O
C, both power
5.5V
2.7V to 5.5V
2.5V to 5.5V
3.3V to 5.5V
C
4.7 F
CER
4.7 F
CER
4.7 F
CER
Synchronous Buck Converter
C
C
OUT
OUT
V
OUT
V
V
IN
IN
IN
Figure 6: 1.5V Step-Down Regulator
Figure 5: 1.2V Step-Down Regulator
Figure 7: 2.5V Step-Down Regulator
IN
EN
EN
IN
IN
EN
AME5258
AME5258
AME5258
GND
GND
GND
SW
SW
SW
FB
FB
FB
1.5MHz, 600mA
316K
604K
316K
2.2 H
2.2 H
2.2 H
604K
475K
22pF
22pF
22pF
1M
Rev.A.05
V
1.2V
V
V
2.5V
1.5V
OUT
CER
OUT
CER
OUT
CER
C
10 F
C
10 F
C
10 F
OUT
OUT
OUT