Rainbow Electronics MAX15020 - Manual (Page 10)

MAX15020
2A, 40V Step-Down DC-DC Converter with
Dynamic Output-Voltage Programming
10 ______________________________________________________________________________________
MAX15020
ON/OFF
IN
D2
D1
C4
1
µF
L1
22 µH V OUT
DVREG LX
REG
REFIN
SS
R5
10
Ω
R1
97.5k Ω
R2
4.02k Ω
C1
560 µF
R7
10k
Ω
R8
340
Ω
C7
0.1 µF
C11
0.027 µF
C6
560 µF
R3
10k Ω
C9
0.1
µF
C2
1
µF
C10
1
µF
C3
0.1
µF
V IN
7.5V TO 40V
PWM
INPUT
0 Ω
BST
R6
10k Ω
C13
330pF
C12
0.1 µF
R9
15.8k Ω
FB
COMP
C8
0.22 µF
REFOUT
C5
0.1 µF
SYNC GND FSEL PGND EP
Figure 2. Typical Application Circuit
Detailed Description
The MAX15020 voltage-mode step-down converter
contains an internal 0.2Ω power MOSFET switch. The
MAX15020 input voltage range is 7.5V to 40V. The
internal low R
DS(ON) switch allows for up to 2A of out-
put current. The external compensation, voltage feed-
forward, and automatically adjustable maximum ramp
amplitude simplify the loop compensation design allow-
ing for a variety of L and C filter components. In shut-
down, the supply current is typically 6µA. The output
voltage is dynamically adjustable from 0.5V to 36V.
Additional features include an externally programmable
UVLO through the ON/OFF pin, a programmable soft-
start, cycle-by-cycle current limit, hiccup-mode output
short-circuit protection, and thermal shutdown.
Internal Linear Regulator (REG)
REG is the output terminal of the 8V LDO powered from
IN and provides power to the IC. Connect REG exter-
nally to DVREG to provide power for the internal digital
circuitry. Place a 1µF ceramic bypass capacitor, C2,
next to the IC from REG to GND. During normal opera-
tion, REG is intended for powering up only the internal
circuitry and should not be used to supply power to the
external loads.
UVLO/ON/
OFF Threshold
The MAX15020 provides a fixed 7V UVLO function
which monitors the input voltage (V
IN ). The device is
held off until V
IN
rises above the UVLO threshold.
ON/OFF provides additional turn-on/turn-off control.
Program the ON/OFF threshold by connecting a resis-
tive divider from IN to ON/OFF to GND. The device
turns on when V
ON/OFF
rises above the ON/OFF thresh-
old (1.225V), given that V IN has risen above the UVLO
threshold.
Driving ON/OFF to ground places the IC in shutdown.
When in shutdown the internal power MOSFET turns
off, all internal circuitry shuts down, and the quiescent
supply current reduces to 6µA (typ.). Connect an RC
network from ON/OFF to GND to set a turn-on delay
that can be used to sequence the output voltages of
multiple devices.