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MAX5080 View Datasheet(PDF) - Maxim Integrated

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MAX5080 Datasheet PDF : 19 Pages
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1A, 40V, MAXPower Step-Down
DC-DC Converters
ON/OFF
C-
C+
DVREG
REG
ISS
SS
FB
COMP
IN
LDO
EN
1.23V
1.23V
>1.23V ON
<1.11V OFF
REF
VREF
THERMAL
SHDN
1.23V
E/A
REGOK
SSA
DVREG
PCLK
LEVEL
SHIFT
OVERL OVERLOAD
MANAGEMENT
EN
MAX5080
ILIM
CLK
ILIM
REF_ILIM
VREF
PFM
HIGH-SIDE
CURRENT
REF_PFM
SENSE
SYNC
EN
OSC
IN
RAMP
CPWM
0.3V
CLK
LOGIC
CHARGE-PUMP
MANAGEMENT
PCLK
SCLK
DVREG
SGND
IN
BST
LX
PGND
Figure 1. MAX5080 Simplified Block Diagram
Internal Linear Regulator (REG)
REG is the output terminal of a 5V (MAX5080), or 8V
(MAX5081) LDO which is powered from IN and pro-
vides power to the IC. Connect REG externally to
DVREG to provide power for the high-side MOSFET
gate driver. Bypass REG to SGND with a ceramic
capacitor of at least 1µF. Place the capacitor physically
close to the MAX5080/MAX5081 to provide good
bypassing. During normal operation, REG is intended
for powering up only the internal circuitry and should
not be used to supply power to external loads.
Internal UVLO/External UVLO
The MAX5080/MAX5081 provides two undervoltage
lockouts (UVLOs). An internal UVLO looks at the input
voltage (VIN) and is fixed at 4.1V (MAX5080) or 7.1V
(MAX5081). An external UVLO is sensed and pro-
grammed at the ON/OFF pin. The external UVLO over-
rides the internal UVLO when the external UVLO is
higher than the internal UVLO. During startup, before
any operation begins, the input voltage and the voltage
at ON/OFF must exceed their respective UVLOs. The
external UVLO has a rising threshold of 1.23V with
0.12V of hysteresis. Program the external UVLO by
connecting a resistive divider from IN to ON/OFF to
SGND. Connect ON/OFF to IN directly to disable the
external UVLO.
Driving ON/OFF to ground places the MAX5080/
MAX5081 in shutdown. When in shutdown the internal
power MOSFET turns off, all internal circuitry shuts
down and the quiescent supply current reduces to
200µA. Connect an RC network from ON/OFF to SGND
to set a turn-on delay that can be used to sequence the
output voltages of multiple devices.
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