AAT2786 Datasheet, PDF (25/27 Pages) Advanced Analogic Technologies – 1.5A Step-Down Converter and 150mA LDO

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PRODUCT DATASHEET
AAT2786
1.5A Step-Down Converter and 150mA LDO
AAT2786 Losses
Total losses can be estimated by calculating the dropout (V_IN = V_OBUCK) losses where the power MOSFET R_DS(ON) will be
at the maximum value. All values assume an 85°C ambient temperature and a 120°C junction temperature with the
TDFN 50°C/W package.
P_TOTAL
=
I²
OBUCK
·
R_DS(ON)H
+
(V_INLDO
-
V_OUTLDO)
·
I_OLDO
= 1.5A² · 0.16Ω + (4.2 - 2.5) · 150mA
= 615mW
T_J(MAX) = T_AMB + Θ_JA · P_LOSS = 85°C + (50°C/W) · 615mW = 116°C
The total losses are also investigated at the nominal lithium-ion battery voltage (3.6V). The simplified version of the
R_DS(ON) losses assumes that the N-channel and P-channel R_DS(ON) are equal.
P_TOTAL
=
I²
OBUCK
·
R_DS(ON)H
+
(t_sw
·
F_S
·
I_BUCK
+
I_QBUCK)
·
V_INBUCK
+
(V_INLDO
-
V_OUTLDO)
-
I_OLDO
= 1.5A² · 152mΩ + (5ns · 1.2MHz · 1.5A + 50µA) · 3.6V + (4.2V - 2.5V) · 150mA
= 630mW
T_J(MAX) = T_AMB + Θ_JA · P_LOSS = 85°C + (50°C/W) · 6300mW = 117°C
V_OUT (V)
3.3
2.5
1.8
1.5
1.2
1.0
0.8
0.6
Inductance
(µH)
3.3
2.2
1.8
1.8
1.2
1.0
1.0
1.0
Part
Number
CDRH4D28
CDRH4D28
CDRH4D28
CDRH4D28
CDRH4D28
SD3114-1.0
SD3114-1.0
SD3114-1.0
Manufacturer
Sumida
Sumida
Sumida
Sumida
Sumida
Cooper
Cooper
Cooper
Size (mm)
5x5x3
5x5x3
5x5x3
5x5x3
5x5x3
3.1x3.1x1.45
3.1x3.1x1.45
3.1x3.1x1.45
Rated
Current
(A)
1.57
2.04
2.2
2.2
2.56
Table 2: Surface Mount Inductors.
I_RMS
(A)
I_SAT
(A)
1.67
1.67
1.67
2.07
2.07
2.07
DCR (Ω)
36.4
23.2
20.4
20.4
17.5
0.042
0.042
0.042
Manufacturer
Murata
Murata
Part Number
GRM21BR60J106KE19
GRM21BR60J226ME39
Value
10µF
22µF
Voltage
6.3V
6.3V
Table 3: Surface Mount Capacitors.
Temp. Co.
X5R
X5R
Case
0805
0805
2786.2008.04.1.0
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