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PDF MAX8614A Data sheet ( Hoja de datos )
| Número de pieza | MAX8614A | |
| Descripción | (MAX8614A / MAX8614B) Dual-Output (+ and -) DC-DC | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-4014; Rev 0; 3/06
Dual-Output (+ and -) DC-DC
Converters for CCD
General Description
The MAX8614A/MAX8614B dual-output step-up DC-DC
converters generate both a positive and negative sup-
ply voltage that are each independently regulated. The
positive output delivers up to 50mA while the inverter
supplies up to 100mA with input voltages between 2.7V
and 5.5V. The MAX8614A/MAX8614B are ideal for pow-
ering CCD imaging devices and displays in digital
cameras and other portable equipment.
The MAX8614A/MAX8614B generate an adjustable
positive output voltage up to +24V and a negative out-
put down to 16V below the input voltage. The
MAX8614B has a higher current limit than the
MAX8614A. Both devices operate at a fixed 1MHz fre-
quency to ease noise filtering in sensitive applications
and to reduce external component size.
Additional features include pin-selectable power-on
sequencing for use with a wide variety of CCDs, True
Shutdown™, overload protection, fault flag, and internal
soft-start with controlled inrush current.
The MAX8614A/MAX8614B are available in a space-
saving 3mm x 3mm 14-pin TDFN package and
are specified over the -40°C to +85°C extended
temperature range.
Applications
CCD Bias Supplies and OLED Displays
Digital Cameras
Camcorders and Portable Multimedia
PDAs and Smartphones
True Shutdown is a trademark of Maxim Integrated Products, Inc.
Pin Configuration
TOP VIEW
14 13 12 11 10 9 8
MAX8614A
MAX8614B
+
1234567
TDFN
Features
♦ Dual Output Voltages (+ and -)
♦ Adjustable Up to +24V and Down to -10V at 5.5VIN
♦ Output Short/Overload Protection
♦ True Shutdown on Both Outputs
♦ Controlled Inrush Current During Soft-Start
♦ Selectable Power-On Sequencing
♦ Up to 90% Efficiency
♦ 1µA Shutdown Current
♦ 1MHz Fixed-Frequency PWM Operation
♦ Fault-Condition Flag
♦ Thermal Shutdown
♦ Small, 3mm x 3mm, 14-Pin TDFN Package
Ordering Information
PART
TEMP PIN-
TOP
ILIM
RANGE PACKAGE MARK BST/INV
MAX8614AETD+
-40°C to
+85°C
14 TDFN
3mm x 3mm
(T1433-2)
ABG
0.44/0.33
MAX8614BETD+
-40°C to
+85°C
14 TDFN
3mm x 3mm
(T1433-2)
+Denotes lead-free package.
ABH
0.8/0.75
Typical Operating Circuit
INPUT
(2.7V TO 5.5V)
VCC
ONINV
ONBST
AVCC
MAX8614A
MAX8614B
REF
LXN
FBN
PVP
AVCC
SEQ
LXP
FLT
GND
PGND
FBP
VINV
-7.5V
REF
VBST
+15V
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
Dual-Output (+ and -) DC-DC
Converters for CCD
Typical Operating Characteristics
(TA = +25°C, VCC = VAVCC = 3.6V, SEQ = GND, Figure 1, unless otherwise noted.)
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
350
300
VOUT = 10V
250
200 VOUT = 15V
150
100
50
VOUT = 20V
0
2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
100
90
80
70
60
50
40
30
20
10
0
0.1
POSITIVE OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
VCC = 5V
VCC = 3.6V
VCC = 4.2V
VCC = 3V
L = 10µH, C = 10µF
1 10
OUTPUT CURRENT (mA)
100
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
300
VINV = -5V
250
200
150 VINV = -7.5V
100
VINV = -10V
50
0
2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
NEGATIVE OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
100
VCC = 3.6V
90
VCC = 3V
80
70
60
50 VCC = 4.2V
40 VCC = 5V
30
20
10
0
0.1
L = 4.7µH, C = 4.7µF
1 10
OUTPUT CURRENT (mA)
100
100
90
80
70
60
50
40
30
20
10
0
0.1
POSITIVE OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
VCC = 5V
VCC = 3V
VCC = 4.2V
VCC = 3.6V
L = 2.2µH, C = 2.2µF
1 10
OUTPUT CURRENT (mA)
100
NEGATIVE OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
100
VCC = 3.6V
90
VCC = 3V
80
70
60
50 VCC = 4.2V
40
VCC = 5V
30
20
10
0
0.1
L = 10µH, C = 10µF
1 10
OUTPUT CURRENT (mA)
100
OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
100
90 VCC = 5V
80
70
60
50
VCC = 3V VCC = 4.2V
40 VCC = 3.6V
30
20
10 BOTH OUTPUTS LOADED EQUALLY
L1 = 2.2µH, C1 = 2.2µF, L2 = 4.7µH, C2 = 4.7µF
0
0.1 1 10 100
OUTPUT CURRENT (mA)
OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
100 VCC = 5V
90
80
70 VCC = 4.2V
60 VCC = 3V
50
40 VCC = 3.6V
30
20
10 BOTH OUTPUTS LOADED EQUALLY
L1 = 10µH, C1 = 10µF, L2 = 10µH, C2 = 10µF
0
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
_______________________________________________________________________________________ 5
5 Page 
Dual-Output (+ and -) DC-DC
Converters for CCD
the inverter output, load disconnect is implemented by
turning off the inverter’s internal power switch.
Current-Limit Select
The MAX8614B allows an inductor current limit of 0.8A
on the step-up converter and 0.75A on the inverter. The
MAX8614A allows an inductor current limit of 0.44A on
the step-up converter and 0.33A on the inverter. This
allows flexibility in designing for higher load-current
applications or for smaller, more compact designs
when less power is needed. Note that the currents list-
ed above are peak inductor currents and not output
currents. The MAX8614B output current is 50mA at
+15V and 100mA at -7.5V. The MAX8614A output cur-
rent is 25mA at +15V and 50mA at -7.5V.
Load Transient/Voltage Positioning
The MAX8614A/MAX8614B match the load regulation to
the voltage droop seen during load transients. This is
sometimes called voltage positioning. This results in min-
imal overshoot when a load is removed and minimal volt-
age drop during a transition from light load to full load.
The use of voltage positioning allows superior load-
transient response by minimizing the amplitude of over-
shoot and undershoot in response to load transients.
DC-DC converters with high control-loop gains maintain
tight DC load regulation but still allow large voltage
drops of 5% or greater for several hundred microsec-
onds during transients. Load-transient variations are
seen only with an oscilloscope (see the Typical
Operating Characteristics). Since DC load regulation is
read with a voltmeter, it does not show how the power
supply reacts to load transients.
Applications Information
Adjustable Output Voltage
The positive output voltage is set by connecting FBP to
a resistive voltage-divider between the output and GND
(Figure 1). Select feedback resistor R2 in the 30kΩ to
100kΩ range. R1 is then given by:
R1 =
R2
⎛ VBST
⎝⎜ VFBP
−
⎞
1⎠⎟
where VFBP = 1.01V.
The negative output voltage is set by connecting FBN
to a resistive voltage-divider between the output and
REF (Figure 1). Select feedback resistor R4 in the 30kΩ
to 100kΩ range. R3 is then given by:
R3
=
R4
×
⎛
⎝⎜
VFBN − VIMV
VREF − VFBN
⎞
⎠⎟
where VREF = 1.25V and VFBN = 0V.
Inductor Selection
The MAX8614A/MAX8614B high switching frequency
allows for the use of a small inductor. The 4.7µH and
2.2µH inductors shown in the Typical Operating Circuit is
recommended for most applications. Larger inductances
reduce the peak inductor current, but may result in skip-
ping pulses at light loads. Smaller inductances require
less board space, but may cause greater peak current
due to current-sense comparator propagation delay.
Use inductors with a ferrite core or equivalent. Powder
iron cores are not recommended for use with high switch-
ing frequencies. The inductor’s incremental saturation rat-
ing must exceed the selected current limit. For highest
efficiency, use inductors with a low DC resistance (under
200mΩ); however, for smallest circuit size, higher resis-
tance is acceptable. See Table 1 for a representative list
of inductors and Table 2 for component suppliers.
Diode Selection
The MAX8614A/MAX8614B high switching frequency
demands a high-speed rectifier. Schottky diodes, such
as the CMHSH5-2L or MBR0530L, are recommended.
Make sure that the diode’s peak current rating exceeds
the selected current limit, and that its breakdown volt-
age exceeds the output voltage. Schottky diodes are
preferred due to their low forward voltage. However,
ultrahigh-speed silicon rectifiers are also acceptable.
Table 2 lists component suppliers.
Capacitor Selection
Output Filter Capacitor
The primary criterion for selecting the output filter
capacitor is low effective series resistance (ESR). The
product of the peak inductor current and the output fil-
ter capacitor’s ESR determines the amplitude of the
high-frequency ripple seen on the output voltage.
These requirements can be balanced by appropriate
selection of the current limit.
For stability, the positive output filter capacitor, C1,
should satisfy the following:
C1 > (6L IBSTMAX ) / ( RCS D+ VBST2 )
where RCS = 0.015 (MAX8614B), and 0.035 (MAX8614A).
D+ is 1 minus the step-up switch duty cycle and is:
D+ = VCC / VBST
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet MAX8614A.PDF ] | |
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