MAX5082 查看數據表（PDF） - Maxim Integrated
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MAX5082 Datasheet PDF : 18 Pages
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1.5A, 40V, MAXPower Step-Down
DC-DC Converters
IN
LDO
REG
EN
ON/OFF
1.23V
>1.23V ON
<1.11V OFF
1.23V
MAX5083
SGND
ISS
REF
VREF
THERMAL
SHDN
SS
FB
COMP
SYNC
1.23V
E/A
IN
CPWM
EN
OSC
RAMP
0.3V
CLK
REGOK
SSA
OVERL OVERLOAD
ILIM
MANAGEMENT
CLK
EN
ILIM
REF_ILIM
VREF
PFM
REF_PFM
HIGH-SIDE
CURRENT
SENSE
LOGIC
BOOTSTRAP
ILIM CONTROL
PCLK
SCLK
IN
BST
LX
DVREG
PGND
Figure 2. MAX5083 Simplified Block Diagram
Soft-Start and Reference (SS)
SS is the 1.23V reference bypass connection for the
MAX5082/MAX5083 and also controls the soft-start
period. At startup, after VIN is applied and the internal
and external UVLO thresholds are reached, the device
enters soft-start. During soft-start, 15µA is sourced into
the capacitor (CSS) connected from SS to SGND caus-
ing the reference voltage to ramp up slowly. When VSS
reaches 1.23V the output becomes fully active. Set the
soft-start time (tSS) using the following equation:
tSS
=
1.23V × CSS
15µA
where tSS is in seconds and CSS is in Farads.
Internal Charge Pump (MAX5082)
The MAX5082 features an internal charge pump to
enhance the turn-on of the internal MOSFET, allowing
for operation with input voltages down to 4.5V. Connect
a flying capacitor (CF) between C+ and C-, a boost
diode from C+ to BST, as well as a bootstrap capacitor
(CBST) between BST and LX to provide the gate-drive
voltage for the high-side n-channel DMOS switch.
During the on-time, the flying capacitor is charged to
VDVREG. During the off-time, the positive terminal of the
flying capacitor (C+) is pumped to two times VDVREG
and charge is dumped onto CBST to provide twice the
regulator voltage across the high-side DMOS driver.
Use a ceramic capacitor of at least 0.1µF for CBST and
CF located as close to the device as possible.
For applications that do not require a 4.5V minimum
input, use the MAX5083. In this device, the charge
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