MAX5039 MAXIM [Maxim Integrated Products], MAX5039 Datasheet - Page 12

• Manufacturer Part Number: MAX5039
• Description: Voltage-Tracking Controllers for PowerPC, DSPs, and ASICs
• Manufacturer: MAXIM [Maxim Integrated Products]

UVLO is a user-programmable undervoltage lockout
input. When the UVLO voltage is above V
MAX5039/MAX5040 hold SDO high, given that V
within its operating range and there is no fault condition
present. When the UVLO voltage falls below V
SDO is pulled low. Use a resistor-divider from the input
of the CORE and I/O power supplies to UVLO to GND
to set the undervoltage lockout (see the Typical
Application Circuit). The MAX5039/MAX5040 keep the
CORE and I/O power supplies off (through the SDO)
until their input voltage is within its operating range.
UVLO can be used to turn off the CORE and I/O power
supplies through SDO. Pull the UVLO pin low with an
open-collector driver to assert SDO, which turns off the
power supplies.
The MAX5039/MAX5040 contain an internal 20Ω N-
channel MOSFET bleeder that connects CORE to
ground. The bleeder turns on whenever the MAX5039/
MAX5040 hold SDO low and V
turn-on voltage threshold (2.43V). This bleeder assists
in discharging the output capacitor(s) during power-
down/brownout conditions. The MAX5039/MAX5040
maintain tight voltage tracking of the CORE and I/O
Voltage-Tracking Controllers for
PowerPC, DSPs, and ASICs
Figure 10. Typical Application Circuit for the MAX5040
12
______________________________________________________________________________________
1µF
C
IN
V
IN
(5V)
R7
25.5kΩ
1%
R8
10kΩ
1%
IN
IN
UVLO
V
CC
SUPPLY
SUPPLY
POWER
POWER
CORE
I/O
CC
SHDN
SHDN
SDO
is above the V
MAX5040
OUT
OUT
GND
Active Bleeder
CORE
I/O_SENSE
UVCC
CORE_FB
I/O
NDRV
13.3kΩ
POK
UVLO
10kΩ
UVCC
CC
CC
1%
1%
, the
R5
R6
IC
is
,
100nF
C1
voltages, as long as V
range. It is important to discharge the output capacitors
to ground before V
illustrates a method to prolong V
down/brownout condition.
The hold-up capacitor, C
up and provides the power to the MAX5039/MAX5040
to keep them in operation even after V
down.
The MAX5039/MAX5040 prevent premature turning on
of the CORE and I/O power supplies during power-up
by actively holding SDO low as soon as V
above 0.9V, provided the condition for SDO to stay low
is valid. The MAX5039/MAX5040 completely turn on
and NDRV is operational when V
V
the MAX5039/MAX5040 maintain tight tracking of the
CORE and I/O output voltages. The MAX5039/
MAX5040 continue to hold SDO low until the UVLO volt-
age rises above V
Once the UVLO voltage rises above V
high, enabling the CORE and I/O power supplies at the
same time. Without voltage tracking, depending on the
CC
1.5nF
C2
IC turn-on voltage threshold (2.43V). In this state,
Q1
Si9428
SO-8
C
100µF
CORE
10kΩ
R3
10kΩ
0.1%
R1
V
V
I/O
CORE
= 3.3V AT 2.0A
UVCC
R2A
9.09kΩ
0.1%
R2B
158Ω
1%
= 1.8V AT 2.0A
CC
C
100µF
R9
1kΩ
5%
C3
22nF
CC
I/O
drops out of its range. Figure 11
(1.230V).
HD
is within its operating voltage
50Ω
R4
, holds the voltage at V
CC
I/O
CORE
CC
UVCC
DSP/ASIC
PowerPC/
rises above the
after a power-
GPIO
IN
Power-Up
, SDO goes
has gone
CC
rises
CC