MAX1584ETJ+ Maxim Integrated Products, MAX1584ETJ+ Datasheet - Page 25

• Manufacturer Part Number: MAX1584ETJ+
• Description: IC DGTL CAM PWR-SUP 5CH 32TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX1584ETJ+

• Applications: Controller, Digital Camera
• Voltage - Input: 0.7 ~ 5.5 V
• Number Of Outputs: 5
• Voltage - Output: 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

Figure 6. AUX_ Channel Powering a White LED Step-Up
Current Source
On the MAX1585, AUX2 is set up to drive an external P-
channel MOSFET in an inverting configuration. DL2 dri-
ves low to turn on the MOSFET, and FB2 has inverted
polarity and a 0V threshold. This is useful for generating
negative CCD bias without a transformer, particularly
with high pixel-count cameras that have a greater neg-
ative CCD load current. Figures 1 and 8 show such a
configuration for the MAX1585.
Another method of producing bipolar output voltages
without a transformer is with an AUX controller and a
charge-pump circuit as shown in Figure 9. When MOS-
FET Q1 turns off, the voltage at its drain rises to supply
current to V
voltage V
C1 discharges through D3, thereby charging C3 to V
minus the drop across D3 to create roughly the same
voltage as V
If different magnitudes are required for the positive and
negative voltages, a linear regulator can be used at one
of the outputs to achieve the desired voltages. One such
Transformerless Inverter for Negative CCD
Boost with Charge Pump for Positive and
V
BATT
OUT+
TO
OUT+
OUT+
62Ω
(FOR 20mA)
WHITE
LEDS
through D1. When the MOSFET turns on,
1μF
1μF
. At the same time, C1 charges to the
at V
NOTE: THIS CIRCUIT CAN
OPERATE WITH AUX1 OR
AUX2 ON THE MAX1584, AND WITH
AUX1 ON THE MAX1585.
______________________________________________________________________________________
OUT-
, but with inverted polarity.
Bias (AUX2, MAX1585)
5-Channel Slim DSC Power Supplies
DL_
FB_
Negative Outputs
(PARTIAL)
MAX1585
PVSU
AUX_
PWM
OUT-
connection is shown in Figure 10. This circuit is some-
what unique in that a positive-output linear regulator is
able to regulate a negative voltage output. It does this by
controlling the charge current flowing to the flying
capacitor rather than directly regulating at the output.
The MAX1584/MAX1585s’ internal switch step-up and
step-down can be cascaded to make a high-efficiency
boost-buck converter, but it is sometimes desirable to
build a second boost-buck converter with an AUX_
controller.
One type of step-up/step-down converter is the SEPIC,
shown in Figure 11. Inductors L1 and L2 can be sepa-
rate inductors or can be wound on a single core and
coupled like a transformer. Typically, a coupled inductor
improves efficiency since some power is transferred
through the coupling so less power passes through the
coupling capacitor (C2). Likewise, C2 should have low
ESR to improve efficiency. The ripple-current rating must
be greater than the larger of the input and output cur-
rents. The MOSFET (Q1) drain-source voltage rating and
the rectifier (D1) reverse-voltage rating must exceed the
sum of the input and output voltages. Other types of
step-up/step-down circuits are a flyback converter and a
step-up converter followed by a linear regulator.
Figure 7. +15V and -7.5V CCD Bias with Transformer
NOTE: THIS CIRCUIT CAN OPERATE WITH AUX1
OR AUX2 ON THE MAX1584, AND WITH AUX1 ON THE MAX1585.
(PARTIAL)
MAX1584
MAX1585
PWM
AUX
PVSU
DL_
FB_
V
BATT
TO
Q1
SEPIC Boost-Buck
D2
+15V
50mA
CCD+
-7.5V
30mA
CCD-
25