ame5251 AME, Inc., ame5251 Datasheet - Page 9

• Manufacturer Part Number: ame5251
• Description: Dual 1a, 1.5mhz Synchronous Step-down Converter
• Manufacturer: AME, Inc.

Output Voltage Programming
according to the following equation :
much heat due to its high efficiency. But, in applications
where the AME5251 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 AME5251 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:
Rev.A.02
AME5251
Thermal Considerations
to the ambient temperature.
vider allows the FB pin to sense a fraction of the output
voltage as shown in Figure 5.
JA
The output voltage is set by an external resistive divider
In most applications the AME5251 does not dissipate
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 5: Setting the AME5251 Output Voltage
R
V
AME5251
OUT
(
PD
GND
AME
)(
V
FB
REF
JA
)
0.6V
1 (
R
R
V
1
2
OUT
)
R1
R2
O
5.5V
C, both power
Dual 1A, 1.5MHz Synchronous
2.5V to 5.5V
4.7 F
CER
2.7V to 5.5V
C
3.3 to 5.5V
4.7 F
IN
4.7 F
V
CER
CER
C
C
IN
V
IN
Figure 6: 1.2V Step-Down Regulator
V
Figure 7: 1.5V Step-Down Regulator
IN
Figure 8: 2.5V Step-Down Regulator
IN
IN
EN
IN
IN
EN
EN
IN
AME5251
Step-Down Converter
AME5251
AME5251
GND
GND
GND
SW
SW
SW
FB
FB
FB
22pF
22pF
22pF
150K
2.2 H
2.2 H
2.2 H
47.3K
100K
150K
150K
150K
V
V
V
OUT
OUT
OUT
1.2V
1.5V
2.5V
10 F
C
CER
10 F
10 F
C
CER
C
CER
OUT
OUT
OUT
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