MAX1565ETJ+T Maxim Integrated Products, MAX1565ETJ+T Datasheet - Page 24

• Manufacturer Part Number: MAX1565ETJ+T
• Description: IC DGTL CAM PWR-SUP 5CH 32TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX1565ETJ+T

• Applications: Converter Controller, Digital Cameras
• Voltage - Input: 0.7 ~ 5.5 V
• Number Of Outputs: 5
• Voltage - Output: 3.3V, 1.25 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

SDOK goes low when the step-down reaches regula-
tion. Some microcontrollers with low-voltage cores
require that the high-voltage (3.3V) I/O rail not be
powered up until the core has a valid supply. The
circuit in Figure 12 accomplishes this by driving the
gate of a PFET connected between the 3.3V output and
the microcontroller I/O supply. Alternately, power
sequencing may be implemented by connecting RC
networks to the appropriate converter ON_ inputs.
The step-down feedback voltage is 1.25V when
FBSELSD is high. With a standard two-resistor feed-
back network, the output voltage may be set to values
between 1.25V and the input voltage. If a step-down
output voltage less than 1.25V is desired, it can be set by
adding a third feedback resistor from FB to a voltage
higher than 1.25V (the step-up output is a convenient
voltage for this) as shown in Figure 13.
The equation governing output voltage shown in Figure
13 is:
where V
V
able voltage that is higher than 1.25V can be used as
the connection point for R3 in Figure 13 and for the V
term in the equation. Since there are multiple solutions
for R1, R2, and R3, the above equation cannot be writ-
ten in terms of one resistor. The best method for deter-
mining resistor values is to enter the above equation
into a spreadsheet and test estimated resistors’ values.
A good starting point is with 100kΩ at R2 and R3.
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
Figure 11. Connecting the MAX1801 Slave PWM Controller to the MAX1565
24
SU
is the step-up output voltage. Note that any avail-
______________________________________________________________________________________
0 = [(V
SD
Using SDOK for Power Sequencing
is the output voltage, V
+ [(V
SD
- V
SU
Setting OUTSD Below 1.25V
FBSD
- V
FBSD
)/R1] + [(0 - V
V
OUT
)/R3]
FBSD
FBSD
is 1.25V, and
)/R2]
DL
FB
COMP
GND
SD
TO BATT
MAX1801
DCON
Figure 12. Using SDOK to Gate 3.3V Power to CPU After the
Core Voltage is OK
OSC
REF
IN
STEP-DOWN
STEP-UP
(PARTIAL)
MAX1565
PGNDA
OUTSU
OSC
REF
OUTSUB
OUTSUA
(PARTIAL)
MAX1565
PGNDB
SDOK
LXSU
FBSU
LXSD
FBSD
INSD
4.7µH
10µH
1
10µF
0µF
VBATT
TO
TO V
OR OUTSU
BATT
1MΩ
10µF
V
1.5V
CORE
1MΩ
3.35V
3.3V
TO
CPU