Datasheet

use typical values of V
IN
and f
SW
so that efficien-
cy is optimum for typical conditions. The switching
frequency (f
SW
) is fixed at 135kHz (MAX5096) and
330kHz (MAX5097). f
SW
can also be varied from 120kHz
to 500kHz (MAX5096) and from 300kHz to 500kHz
(MAX5097) when synchronized to an external clock (see
the Oscillator/Synchronization Input (SYNC) section). The
peak-to-peak inductor current, which reflects the peak-to-
peak output ripple, is worst at the maximum input voltage.
See the Output Capacitor Selection section to verify that
the worst-case output ripple is acceptable. The induc-
tor saturating current (I
SAT
) is also important to avoid
runaway current during continuous output short circuit.
Select an inductor with an I
SAT
specification higher than
the maximum peak current limit of 1.9A.
The buck mode operation determines the inductor and
output capacitor values. However, the values of the
inductor, its DCR, and the output capacitance/ESR affect
the closed-loop-transfer function both in buck and LDO
modes. The internal compensation of the MAX5096/
MAX5097 in LDO mode limits the values of these exter-
nal components. Make sure that the combination of
output inductor, capacitor, and ESR falls within the range
specified in Table 1.
Output Capacitor Selection
The allowable output-voltage ripple and the maximum
deviation of the output voltage during load steps deter-
mine the output capacitance and its ESR. The output
Figure 4. Adjustable Output Voltage Configuration
Table 1. Inductor/Output Capacitor
Selection
INDUCTOR OUTPUT CAPACITOR (C
OUT
)
22μH
22μF, ESR = 5mΩ to 20mΩ (ceramic)
47μF, ESR = 40mΩ to 150mΩ
100μF, ESR = 30mΩ to 100mΩ
470μF/ESR = 60Ω to 400mΩ
47μH
22μF, ESR = 5mΩ to 20mΩ (ceramic)
47μF/ESR = 40mΩ to 150mΩ
100μF/ESR = 30mΩ to 100mΩ
470μF/ESR = 60mΩ to 400mΩ
100μH
22μF, ESR = 5mΩ to 20mΩ (ceramic)
47μF/ESR = 40mΩ to 150mΩ
100μF/ESR = 30mΩ to 100mΩ
470μF/ESR = 60mΩ to 400mΩ
PGND
OUT
LX
V
IN
GND
BP
5V TO 40V
V
IN
V
OUT
ADJ
22µH
C
OUT
22µF
COMP
SYNC
D1*
B260/
MURS105
C
IN
100µF
LDO/BUCK
RESET
EN
R
C
C
C
CT
SS
C
P
R
PU
+
1.0µF
MAX5096
MAX5097
R1
R2
C
CT
C
SS
RESET
*USE MURS105 IN APPLICATIONS
WHERE LDO MODE QUIESCENT
CURRENT IS CRITICAL.
MAX5096/MAX5097 40V, 600mA Buck Converters with Low-
Quiescent-Current Linear Regulator Mode
www.maximintegrated.com
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