MAX1584 Datasheet, PDF (27/29 Pages) Maxim Integrated Products – 5-Channel Slim DSC Power Supplies

5-Channel Slim DSC Power Supplies
TO BATT
TO
V_BATT
V_OUT
PVSU
DL
IN
MAX1801 ^OSC
FB
COMP
GND
REF
DCON
MAX1584
MAX1585
OSC _(PARTIAL)
REF
MAX1584
MAX1585
(PARTIAL)
PVSU
AUX1
PWM
DL1
D6
FB1
AUX1OK
15V
100mA
Figure 12. Adding a PWM Channel with an External MAX1801
Slave Controller
MAX1584/MAX1585
(PARTIAL)
AUX3 V-MODE
STEP-DOWN
DL3
PWM
FB3
TO PVSU
3.3V
LOGIC
CURRENT-
MODE
STEP-UP
PWM
PV
PVSU
LXSU
TO
V_BATT
L2
PGSU
FBSU
GATED +5V
TO CCD
V_SU
+5V
Figure 14. AUX1OK drives an external PFET that switches 5V to
the CCD only after the +15V CCD bias supply is in regulation.
ON3
SDOK
TO V_BATT
OR PVSU
CURRENT-
MODE
STEP-DOWN
PWM
PVSD
LXSD
TO V_BATT
OR PVSU
+1.5V
PGSD
Figure 13. Using SDOK to Gate 3.3V Power to CPU After the
Core Voltage Is in Regulation
The MAX1801 controller operation and design are simi-
lar to that of the MAX1584/MAX1585 AUX controllers.
All comments in the AUX Controller Component
Selection section also apply to add-on MAX1801 slave
controllers. For more details, refer to the MAX1801 data
sheet.
Using SDOK and AUX1OK for Power Sequencing
The SDOK goes low when the step-down reaches regu-
lation. Some microcontrollers with low-voltage cores
require the high-voltage (3.3V) I/O rail not be powered
up until the core has a valid supply. The circuit in
Figure 13 accomplishes this by driving the gate of a
PFET connected between the 3.3V output and the
processor I/O supply.
Figure 14 shows a similar application where AUX1OK
gates 5V power to the CCD only after the +15V output
is in regulation. Alternately, power sequencing can also
be implemented by connecting RC networks to delay
the appropriate converter ON_ inputs.
Using SCF for Full-Load Startup
The SCF output goes low only after the step-up reaches
regulation. It can be used to drive a P-channel MOSFET
switch that turns off the load of a selected supply in the
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