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MAX5083ATE+T

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18
MAX5082/MAX5083
1.5A, 40V, MAXPower Step-Down
DC-DC Converters
______________________________________________________________________________________ 13
Pick a value for the feedback resistor R5 in Figure 3
(values between 1kΩ and 10kΩ are adequate).
C7 is then calculated as:
f
C
occurs between f
Z2
and f
P2
. The error-amplifier gain
(G
EA
) at f
C
is due primarily to C6 and R5. Therefore,
G
EA(fC)
= 2π x f
C
x C6 x R5 and the modulator gain at
f
C
is:
Since G
EA(fC)
x G
MOD(fC)
= 1, C6 is calculated by:
f
P2
is set at one-half the switching frequency (f
SW
). R6
is then calculated by:
Since R3 >> R6, R3 + R6 can be approximated as R3.
R3 is then calculated as:
f
P3
is set at 5xf
C
. Therefore, C8 is calculated as:
Compensation When f
C
> f
ZESR
For larger ESR capacitors such as tantalum and alu-
minum electrolytic ones, f
ZESR
can occur before f
C
. If
f
ZESR
< f
C
, then f
C
occurs between f
P2
and f
P3
. f
Z1
and
f
Z2
remain the same as before however, f
P2
is now set
equal to f
ZESR
. The output capacitor’s ESR zero fre-
quency is higher than f
LC
but lower than the closed-
loop crossover frequency. The equations that define
the error amplifier’s poles and zeroes (f
Z1
, f
Z2
, f
P1
, f
P2
,
and f
P3
) are the same as before. However, f
P2
is now
lower than the closed-loop crossover frequency. Figure
4 shows the error amplifier feedback as well as its gain
response for circuits that use higher-ESR output capac-
itors (tantalum or aluminum electrolytic).
Pick a value for the feedback resistor R5 in Figure 4 (val-
ues between 1kΩ and 10kΩ are adequate).
C7 is then calculated as:
The error amplifier gain between f
P2
and f
P3
is approxi-
mately equal to R5/R6 (given that R6 << R3). R6 can
then be calculated as:
C6 is then calculated as:
C
C ESR
R
6
6
=
×
OUT
R
Rf
f
LC
C
6
510
2
2
≈
××
C
1
f
LC
7
208 5
=
×××π .R
()
C
C
CRf
8
7
275 1
=
×××
−π
P3
R
fC
3
1
26
≈
××π
LC
.
R
Cf
6
1
2605
=
×××π
SW
C
fLC
RG
C
6
2
5
=
×× ×
×
OUT
MOD(DC)
π
()
G
G
LC f
C
MOD(fC)
MOD(DC)
OUT
=
×× ×2
22
π
C
1
f
LC
7
208 5
=
×××π .R
GAIN
(dB)
V
OUT
REF
R3
COMP
R6
R5
C6
R4
FREQUENCY
CLOSED-LOOP
GAIN
EA
GAIN
f
Z1
f
Z2
f
C
f
P2
f
P3
C8
EA
C7
Figure 3. Error Amplifier Compensation Circuit (Closed-Loop
and Error-Amplifier Gain Plot) for Ceramic Capacitors
MAX5082/MAX5083
1.5A, 40V, MAXPower Step-Down
DC-DC Converters
14 ______________________________________________________________________________________
Since R3 >> R6, R3 + R6 can be approximated as R3.
R3 is then calculated as:
f
P3
is set at 5xf
C
. Therefore, C8 is calculated as:
Power Dissipation
The MAX5082/MAX5083 is available in a thermally
enhanced package and can dissipate up to 2.7W at T
A
=
+70°C. When the die temperature reaches +160°C, the
part shuts down and is allowed to cool. After the part
cools by 20°C, the device restarts with a soft-start.
The power dissipated in the device is the sum of the
power dissipated from supply current (P
Q
), transition
losses due to switching the internal power MOSFET
(P
SW
), and the power dissipated due to the RMS cur-
rent through the internal power MOSFET (P
MOSFET
).
The total power dissipated in the package must be lim-
ited such that the junction temperature does not
exceed its absolute maximum rating of +150°C at maxi-
mum ambient temperature. Calculate the power lost in
the MAX5082/MAX5083 using the following equations:
The power loss through the switch:
P
MOSFET
= I
RMS_MOSFET
2
x R
ON
R
ON
is the on-resistance of the internal power MOSFET
(see the Electrical Characteristics).
The power loss due to switching the internal MOSFET:
where t
R
and t
F
are the rise and fall times of the internal
power MOSFET measured at LX.
The power loss due to the switching supply current
(I
SW
):
P
Q
= V
IN
x I
SW
The total power dissipated in the device will be:
P
TOTAL
= P
MOSFET
+ P
SW
+ P
Q
Chip Information
TRANSISTOR COUNT: 4300
PROCESS: BiCMOS/DMOS
()
P
f
SW
SW
=
××××VI tt
IN OUT R F
4
()
_
PI R
IIIII
D
II
I
II
I
MOSFET RMS MOSFET ON
RMS MOSFET
PK
PK DC
DC
PK OUT
PP
DC OUT
PP
=×
=+×+
[]
×
=+
=−
−
−
2
22
3
2
2
_
∆
∆
()
C
C
CRf
8
7
275 1
=
×××
−π
P3
R
fC
3
1
26
≈
××π
LC
GAIN
(dB)
V
OUT
REF
R3
COMP
R6
R5
C6
R4
FREQUENCY
CLOSED-LOOP
GAIN
EA
GAIN
f
Z1
f
Z2
f
C
f
P2
f
P3
C8
EA
C7
Figure 4. Error Amplifier Compensation Circuit (Closed-Loop
and Error Amplifier Gain Plot) for Higher ESR Output Capacitors
MAX5082/MAX5083
1.5A, 40V, MAXPower Step-Down
DC-DC Converters
______________________________________________________________________________________ 15
Figure 6. MAX5083 Typical Application Circuit
Typical Application Circuits
MAX5082
V
IN
4.5V TO 40V
ON/OFF
C1
10µF
R1
1.4MΩ
R2
549kΩ
C2
0.1µF
C10
0.1µF
PGND
REG
LX
FB
IN
SYNC SGND PGND SS COMP
DVREG
C-
C3
0.1µF
V
OUT
PGND
C4
0.1µF
C9
0.047µF
D1
D2
L1
47µH
C8
820pF
C5
47µF
R6
187Ω
R5
3.01kΩ
C+
BST
C7
22nF
C6
6.8nF
R3
6.81kΩ
R4
4.02kΩ
Figure 5. MAX5082 Typical Application Circuit
MAX5083
V
IN
7.5V TO 40V
ON/OFF
C1
10µF
R1
1.4MΩ
R2
301kΩ
C2
0.1µF
C10
0.1µF
PGND
REG
LX
FB
IN
SYNC SGND PGND SS COMP
DVREG
V
OUT
PGND
C4
0.1µF
C9
0.047µF
D1
D2
L1
47µH
C8
820pF
C5
47µF
R6
187Ω
R5
3.01kΩ
BST
C7
22nF
C6
6.8nF
R3
6.81kΩ
R4
4.02kΩ
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18

MAX5083ATE+T

Mfr. #:
Buy MAX5083ATE+T
Manufacturer:
Maxim Integrated
Description:
Switching Voltage Regulators 1A 40V MAXPower Step-Down
Lifecycle:
New from this manufacturer.
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