MAX8614A [MAXIM]
Dual-Output (+ and -) DC-DC; 双输出（ +和 - ）的DC-DC
| 型号： | MAX8614A |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Dual-Output (+ and -) DC-DC |
| 文件： | 总15页 (文件大小：399K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4014; Rev 0; 3/06
Dual-Output (+ and -) DC-DC
Converters for CCD
General Description
Features
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.
♦ Dual Output Voltages (+ and -)
♦ Adjustable Up to +24V and Down to -10V at 5.5V
♦ Output Short/Overload Protection
♦ True Shutdown on Both Outputs
♦ Controlled Inrush Current During Soft-Start
♦ Selectable Power-On Sequencing
♦ Up to 90% Efficiency
IN
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.
♦ 1µA Shutdown Current
♦ 1MHz Fixed-Frequency PWM Operation
♦ Fault-Condition Flag
♦ Thermal Shutdown
♦ Small, 3mm x 3mm, 14-Pin TDFN Package
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.
Ordering Information
TEMP PIN-
RANGE PACKAGE
TOP
ILIM
PART
MARK BST/INV
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.
14 TDFN
-40°C to
MAX8614AETD+
3mm x 3mm ABG
0.44/0.33
0.8/0.75
+85°C
(T1433-2)
14 TDFN
-40°C to
Applications
CCD Bias Supplies and OLED Displays
3mm x 3mm
+85°C
MAX8614BETD+
ABH
(T1433-2)
+Denotes lead-free package.
Digital Cameras
Camcorders and Portable Multimedia
PDAs and Smartphones
Typical Operating Circuit
INPUT
(2.7V TO 5.5V)
True Shutdown is a trademark of Maxim Integrated Products, Inc.
V
CC
Pin Configuration
V
-7.5V
INV
ONINV
LXN
ONBST
AV
CC
TOP VIEW
MAX8614A
MAX8614B
14 13 12 11 10
9
8
FBN
PVP
REF
REF
AV
CC
MAX8614A
MAX8614B
SEQ
FLT
V
+15V
BST
LXP
FBP
+
2
3
1
4
5
6
7
GND
PGND
TDFN
________________________________________________________________ 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.
Dual-Output (+ and -) DC-DC
Converters for CCD
ABSOLUTE MAXIMUM RATINGS
CC
V
, AV
to GND...................................................-0.3V to +6V
CC
Continuous Power Dissipation (T = +70°C Multilayer Board)
A
LXN to V
-18V to +0.3V
14-Pin 3mm x 3mm TDFN (derate 18.2mW/°C above
CC .............................................................
LXP to PGND..........................................................-0.3V to +33V
REF, ONINV, ONBST, SEQ, FBN, FBP
FLT to GND ..........................................-0.3V to (AV
T = +70°C) ............................................................1454.4mW
A
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
+ 0.3)V
+ 0.3)V
CC
CC
PVP to GND................................................-0.3V to (V
AV to V ..........................................................-0.3V to +0.3V
CC
CC
PGND to GND .......................................................-0.3V to +0.3V
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
= V
= V
V
= 3.6V, PGND = SEQ = GND, C6 = 0.22µF, C1 = 2.2µF, C2 = 4.7µF, Figure 1, T = 0°C to +85°C,
CC
AVCC
ONINV = ONBST A
unless otherwise noted. Typical values are at T = +25°C.)
A
PARAMETER
CONDITIONS
MIN
2.7
TYP
MAX
5.5
UNITS
AV
and V
Voltage Range
CC
(Note 1)
V
V
CC
UVLO Threshold
UVLO Hysteresis
V
rising
2.42
2.55
25
2.66
CC
mV
Step-Up Output Voltage Adjust Range
Inverter Output Voltage Adjust Range
V
24
0
V
V
AVCC
-16
V
- V
(Note 2)
INV
CC
MAX8614B
MAX8614A
MAX8614B
MAX8614A
MAX8614B
MAX8614A
0.7
0.8
0.44
1.05
0.61
0.75
0.33
0.6
0.9
0.52
1.20
0.70
0.85
0.38
1.1
LXP Current Limit
A
A
A
0.34
0.90
0.52
0.65
0.28
LXP Short-Circuit Current Limit
LXN Current Limit
LXN On-Resistance
LXP On-Resistance
PVP On-Resistance
Maximum Duty Cycle
V
V
V
= 3.6V
= 3.6V
= 3.6V
Ω
Ω
Ω
%
CC
CC
CC
0.625
0.15
90
0.3
Step-up and inverter
82
I
I
I
I
0.75
2
1.4
3
AVCC
VCC
Quiescent Current (Switching, No Load)
Quiescent Current (No Switching, No Load)
mA
µA
400
8
800
15
5
AVCC
VCC
T
T
= +25°C
= +85°C
0.1
0.1
A
Shutdown Supply Current
FBP Line Regulation
µA
A
V
= 2.7V to 5.5V
-20
mV/D
CC
mV/
(D - 0.5)
FBN Line Regulation
V
= 2.7V to 5.5V
20
CC
2
_______________________________________________________________________________________
Dual-Output (+ and -) DC-DC
Converters for CCD
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= V
V
= 3.6V, PGND = SEQ = GND, C6 = 0.22µF, C1 = 2.2µF, C2 = 4.7µF, Figure 1, T = 0°C to +85°C,
CC
AVCC
ONINV = ONBST A
unless otherwise noted. Typical values are at T = +25°C.)
A
PARAMETER
CONDITIONS
, MAX8614B
, MAX8614A
, MAX8614B
, MAX8614A
MIN
TYP
-15
-35
17.5
65
MAX
UNITS
I
I
I
I
= I
= I
LXP
LXP
LXN
LXN
ILIMMIN
FBP Load Regulation
FBN Load Regulation
mV/A
ILIMMIN
= I
= I
ILIMMIN
mV/A
ILIMMIN
Oscillator Frequency
Soft-Start Interval
0.93
1.24
1
1.07
1.26
MHz
ms
Step-up and inverter
10
Overload-Protection Fault Delay
FBP, FBN, REFERENCE
REF Output Voltage
100
ms
No load
1.25
10
V
REF Load Regulation
REF Line Regulation
0µA < I
< 50µA
mV
mV
V
REF
3.3V < V
No load
No load
< 5.5V
2
5
AVCC
FBP Threshold Voltage
FBN Threshold Voltage
0.995
-10
1.010
0
1.025
+10
+50
mV
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
= +25°C
= +85°C
= +25°C
= +85°C
= +25°C
= +85°C
= +25°C
= +85°C
= +25°C
= +85°C
= +25°C
= +85°C
-50
+5
FBP Input Leakage Current
FBN Input Leakage Current
LXN Input Leakage Current
LXP Input Leakage Current
PVP Input Leakage Current
FLT Input Leakage Current
V
1.025V
FBP =
nA
nA
µA
µA
µA
+5
-50
-5
+5
+50
+5
+5
+5
+1
20
0.5
1
FBN = -10mV
+5
+0.1
+0.1
+0.1
+0.1
+0.1
+0.1
+0.1
+0.1
10
V
V
V
V
= -12V
= 23V
= 0V
LXN
LXP
PVP
FLT
-5
-5
-1
= 3.6V
µA
FLT Input Resistance
ONINV, ONBST, SEQ LOGIC INPUTS
Logic-Low Input
Fault mode, T = +25°C
Ω
A
2.7V < V
2.7V < V
< 5.5V
< 5.5V
V
V
AVCC
AVCC
Logic-High Input
1.6
Bias Current
T
= +25°C
0.1
µA
A
_______________________________________________________________________________________
3
Dual-Output (+ and -) DC-DC
Converters for CCD
ELECTRICAL CHARACTERISTICS
(V
= V
= V
V
= V = 3.6V, PGND = SEQ = GND, C6 = 0.22µF, C1 = 2.2µF, C2 = 6.7µF, Figure 1, T = -40°C
CC
AVCC
ONINV = ONBST EN A
to +85°C, unless otherwise noted.) (Note 3)
PARAMETER
CONDITIONS
MIN
3
TYP
MAX
5.5
UNITS
A
VCC
= V
Voltage Range
CC
(Note 1)
V
V
V
V
UVLO Threshold
V
rising
2.42
2.82
24
CC
Step-Up Output Voltage Adjust Range
Inverter Output Voltage Adjust Range
V
AVCC
-16
V
- V
(Note 2)
0
INV
CC
MAX8614B
MAX8614A
MAX8614B
MAX8614A
MAX8614B
MAX8614A
0.7
0.34
0.9
0.9
LXP Current Limit
A
A
A
0.52
1.2
LXP Short-Circuit Current Limit
LXN Current Limit
0.52
0.65
0.28
0.70
0.85
0.38
1.1
LXN On-Resistance
PVP On-Resistance
Maximum Duty Cycle
V
V
= 3.6V
= 3.6V
Ω
Ω
%
CC
CC
0.3
Step-up and inverter
82
I
I
I
I
1.4
3
AVCC
VCC
Quiescent Current (Switching, No Load)
Quiescent Current (No Switching, No Load)
mA
800
15
AVCC
VCC
µA
Oscillator Frequency
0.93
1.07
MHz
FBP, FBN, REFERENCE
REF Output Voltage
No load
No load
No load
1.235
0.995
-10
1.260
1.025
+10
V
V
FBP Threshold Voltage
FBN Threshold Voltage
ONINV, ONBST SEQ LOGIC INPUTS
Logic-Low Input
mV
2.7V < V
2.7V < V
< 5.5V
< 5.5V
0.5
V
V
AVCC
AVCC
Logic-High Input
1.6
Note 1: Output current and on-resistance are specified at 3.6V input voltage. The IC operates to 2.7V with reduced performance.
Note 2: The specified maximum negative output voltage is referred to V , and not to GND. With V
= 3.3V, the maximum negative
CC
CC
output is then -12.7V.
Note 3: Specifications to -40°C are guaranteed by design, not production tested.
4
_______________________________________________________________________________________
Dual-Output (+ and -) DC-DC
Converters for CCD
Typical Operating Characteristics
(T = +25°C, V
= V
= 3.6V, SEQ = GND, Figure 1, unless otherwise noted.)
AVCC
A
CC
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
POSITIVE OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
300
250
200
150
100
50
100
90
80
70
60
50
40
30
20
10
0
350
300
250
200
150
100
50
V
= 5V
CC
V
= -5V
INV
V
= 10V
OUT
V
= 3V
CC
V
= 15V
OUT
V
= 4.2V
CC
V
= -7.5V
INV
V
= 3.6V
CC
V
= -10V
INV
V
= 20V
4.0
OUT
L = 2.2µH, C = 2.2µF
0
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
0.1
1
10
100
2.5
3.0
3.5
4.5
5.0
5.5
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
INPUT VOLTAGE (V)
POSITIVE OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
NEGATIVE OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
NEGATIVE OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
V
= 5V
CC
V
= 3.6V
V
= 3.6V
CC
CC
V
= 3V
V
= 3V
CC
CC
V
= 3.6V
= 4.2V
CC
V
CC
V
= 4.2V
V
= 4.2V
CC
CC
V
= 3V
CC
V
= 5V
CC
V
= 5V
CC
L = 10µH, C = 10µF
L = 4.7µH, C = 4.7µF
L = 10µH, C = 10µF
0.1
1
10
100
0.1
1
10
100
0.1
1
10
100
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
OUTPUT EFFICIENCY
vs. OUTPUT CURRENT
100
90
80
70
60
50
40
30
20
10
0
100
V
= 5V
CC
V
= 5V
CC
90
80
70
60
50
40
30
20
10
0
V
= 4.2V
CC
V
= 3V
CC
V
= 3V
CC
V
= 4.2V
CC
V
= 3.6V
V
= 3.6V
CC
CC
BOTH OUTPUTS LOADED EQUALLY
L1 = 2.2µH, C1 = 2.2µF, L2 = 4.7µH, C2 = 4.7µF
BOTH OUTPUTS LOADED EQUALLY
L1 = 10µH, C1 = 10µF, L2 = 10µH, C2 = 10µF
0.1 10 100
1
0.1 10 100
1
1000
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
_______________________________________________________________________________________
5
Dual-Output (+ and -) DC-DC
Converters for CCD
Typical Operating Characteristics (continued)
(T = +25°C, V
= V
= 3.6V, SEQ = GND, Figure 1, unless otherwise noted.)
AVCC
A
CC
CHANGE IN OUTPUT VOLTAGE
vs. OUTPUT CURRENT (NEGATIVE OUTPUT)
CHANGE IN OUTPUT VOLTAGE
vs. LOAD CURRENT (POSITIVE OUTPUT)
0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
-3.5
0
V
- = -7.5V
OUT
V
= 5V
CC
-0.5
V
= 5V
IN
V
= 4.2V
-1.0
-1.5
-2.0
-2.5
-3.0
-3.5
CC
V
= 4.2V
IN
V
= 3V
CC
V
= 3V
IN
V
= 3.6V
V
= 3.6V
CC
IN
0
25
50
75
100
125
0
25
50
75
100
125
150
OUTPUT CURRENT (mA)
LOAD CURRENT (mA)
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
SOFT-START WAVEFORMS
MAX8614A/B toc12
1000
900
800
700
600
500
400
300
200
100
0
SEQ = GND
V
ONINV
V
ONBST
5V/div
0V
AV
CC
10V/div
V
BST
0V
5V/div
V
INV
V
CC
I
IN
100mA/div
0V
4ms/div
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
LINE TRANSIENT
SOFT-START WAVEFORMS
MAX8614A/B toc14
MAX8614A/B toc13
SEQ = AV
CC
V
V
ONINV
ONBST
50mV/div
AC-COUPLED
5V/div
0V
V
BST
10V/div
V
BST
V
IN
3.5V TO 4.5V
TO 3.5V
0V
3.5V
5V/div
V
INV
50mV/div
AC-COUPLED
V
INV
I
IN
100mA/div
0V
40µs/div
4ms/div
6
_______________________________________________________________________________________
Dual-Output (+ and -) DC-DC
Converters for CCD
Typical Operating Characteristics (continued)
(T = +25°C, V
A
= V
= 3.6V, SEQ = GND, Figure 1, unless otherwise noted.)
AVCC
CC
LOAD TRANSIENT (POSITIVE OUTPUT)
LOAD TRANSIENT (NEGATIVE OUTPUT)
MAX8614A/B toc15
MAX8614A/B toc16
20mV/div
AC-COUPLED
V
BST
V
50mV/div
INV
AC-COUPLED
100mV/div
AC-COUPLED
100mV/div
AC-COUPLED
V
V
BST
INV
INV
I
BST
20mA/div
0V
50mA/div
0V
I
20mA TO 50mA
TO 20mA
20mA TO 100mA
TO 20mA
4µs/div
4µs/div
SWITCHING WAVEFORMS (POSITIVE OUTPUT)
SWITCHING WAVEFORMS (POSITIVE OUTPUT)
MAX8614A/B toc18
MAX8614A/B toc17
V
V
BST
BST
50mV/div
50mV/div
AC-COUPLED
AC-COUPLED
10V/div
0V
10V/div
0V
V
I
LX
LX
V
LX
500mA/div
0A
I
LX
500mA/div
0A
I
= 50mA
BST
I
= 20mA
BST
400ns/div
400ns/div
SWITCHING WAVEFORMS (NEGATIVE OUTPUT)
SWITCHING WAVEFORMS (NEGATIVE OUTPUT)
MAX8614A/B toc19
MAX8614A/B toc20
V
INV
50mV/div
AC-COUPLED
V
50mV/div
AC-COUPLED
INV
10V/div
0V
10V/div
0V
V
LX
V
LX
500mA/div
0A
500mA/div
0A
I
LX
I
LX
I
= 20mA
INV
I
= 100mA
INV
400ns/div
400ns/div
_______________________________________________________________________________________
7
Dual-Output (+ and -) DC-DC
Converters for CCD
Typical Operating Characteristics (continued)
(T = +25°C, V
= V
= 3.6V, SEQ = GND, Figure 1, unless otherwise noted.)
AVCC
A
CC
SWITCHING FREQUENCY
vs. TEMPERATURE
REFERENCE VOLTAGE
vs. TEMPERATURE
1.006
1.005
1.004
1.003
1.002
1.001
1.000
0.999
0.998
0.997
0.996
1.2490
1.2485
1.2480
1.2475
1.2470
1.2465
1.2460
1.2455
1.2450
V
= -7.5V
INV
I
= 100mA
OUT
V
= +15V
= 50mA
BST
I
OUT
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
Pin Description
PIN
NAME
FUNCTION
Enable Logic Input. Connect ONBST to AV
as an independent control of the step-up converter.
for automatic startup of the step-up converter, or use ONBST
CC
1
ONBST
Negative Output Feedback Input. Connect a resistor-divider between the negative output and REF with the
center to FBN to set the negative output voltage.
2
FBN
3
4
5
AV
Bias Supply. AV
powers the IC. AV must be connected to V
.
CC
CC
CC
CC
REF
1.25V Reference Voltage Output. Bypass with a 0.22µF ceramic capacitor to GND.
Ground. Connect GND to PGND with a short trace.
GND
Fault Open-Drain Output. Connect a 100kΩ resistor from FLT to AV . FLT is active low during a fault event
and is high impedance in shutdown.
CC
6
7
8
9
FLT
Positive Output-Voltage Feedback Input. Connect a resistor-divider between the positive output and GND
with the center to FBP to set the positive output voltage. FBP is high impedance in shutdown.
FBP
SEQ
Sequence Logic Input. When SEQ = low, power-on sequence can be independently controlled by ONBST
and ONINV. When SEQ = high, the positive output powers up before the negative output.
Enable Logic Input. Connect ONINV to AV
independent control of the inverter.
for automatic startup of the inverter, or use ONINV as an
CC
ONINV
10
11
LXP
Positive Output Switching Inductor Node. LXP is high impedance in shutdown.
Power Ground. Connect PGND to GND with a short trace.
PGND
True-Shutdown Load Disconnect Switch. Connect one side of the inductor to PVP and the other side to LXP.
PVP is high impedance in shutdown.
12
13
PVP
Power Input Supply. V
CC
supplies power for the step-up and inverting DC-DC converters. V
must be
CC
V
CC
connected to AV
.
CC
14
—
LXN
EP
Negative Output Switching Inductor Node. LXN is high impedance in shutdown.
Exposed Pad. Connect exposed paddle to ground.
8
_______________________________________________________________________________________
Dual-Output (+ and -) DC-DC
Converters for CCD
Functional Diagram
ERROR
AMPLIFIER
MAX8614A
MAX8614B
PWM
V
CC
COMPARATOR
INVERTER
CONTROL
LOGIC
LXN
INVERTER
CURRENT SENSE
FBN
REF
REFERENCE
1.25V
ONBST
ONINV
1.01V
BIAS
AND
CONTROL
BLOCK
FLT
SOFT-START
SEQ
AV
CC
1MHz
OSCILLATOR
PVP
LXP
ERROR
AMPLIFIER
PWM
COMPARATOR
STEP-UP
CONTROL
LOGIC
PGND
FBP
STEP-UP
CURRENT SENSE
GND
Step-Up Converter
Detailed Description
The step-up converter generates a positive output volt-
age up to 24V. An internal power switch, internal True-
Shutdown load switch (PVP), and external catch diode
allow conversion efficiencies as high as 90%. The inter-
nal load switch disconnects the battery from the load
by opening the battery connection to the inductor, pro-
viding True Shutdown. The internal load switch stays on
at all times during normal operation. The load switch is
used in the control scheme for the converter and can-
not be bypassed.
The MAX8614A/MAX8614B generate both a positive and
negative output voltage by combining a step-up and an
inverting DC-DC converter on one IC. Both the step-up
converter and the inverter share a common clock. Each
output is independently regulated.
Each output is separately controlled by a pulse-width-
modulated (PWM) current-mode regulator. This allows
the converters to operate at a fixed frequency (1MHz)
for use in noise-sensitive applications. The 1MHz
switching rate allows for small external components.
Both converters are internally compensated and are
optimized for fast transient response (see the Load-
Transient Response/Voltage Positioning section).
_______________________________________________________________________________________
9
Dual-Output (+ and -) DC-DC
Converters for CCD
from 0 to 1V (where 1V is the desired feedback voltage
Inverter
for the step-up converter) while the inverter reference is
ramped down from 1.25V to 0 (where 0 is the desired
feedback voltage for the inverter).
The inverter generates output voltages down to -16V
below V . An internal power switch and external catch
CC
diode allow conversion efficiencies as high as 85%.
During startup, the step-up converter True-Shutdown
load switch turns on before the step-up-converter refer-
ence voltage is ramped up. This effectively limits inrush
current peaks to below 500mA during startup.
Control Scheme
Both converters use a fixed-frequency, PWM current-
mode control-scheme. The heart of the current-mode
PWM controllers is a comparator that compares the
error-amp voltage-feedback signal against the sum of
the amplified current-sense signal and a slope-com-
pensation ramp. At the beginning of each clock cycle,
the internal power switch turns on until the PWM com-
parator trips. During this time the current in the inductor
ramps up, storing energy in the inductor’s magnetic
field. When the power switch turns off, the inductor
releases the stored energy while the current ramps
down, providing current to the output.
Undervoltage Lockout (UVLO)
The MAX8614A/MAX8614B feature undervoltage-lock-
out (UVLO) circuitry, which prevents circuit operation
and MOSFET switching when AV
is less than the
CC
UVLO threshold (2.55V, typ). The UVLO comparator
has 25mV of hysteresis to eliminate chatter due to the
source supply output impedance.
Power-On Sequencing (SEQ)
The MAX8614A/MAX8614B have pin-selectable inter-
nally programmed power-on sequencing. This
sequencing covers all typical sequencing options
required by CCD imagers.
Fault Protection
The MAX8614A/MAX8614B have robust fault and over-
load protection. After power-up the device is set to
detect an out-of-regulation state that could be caused by
an overload or short condition at either output. If either
output remains in overload for more than 100ms, both
converters turn off and the FLT flag asserts low. During a
short-circuit condition longer than 100ms on the positive
output, foldback current limit protects the output. During
a short-circuit condition longer than 100ms on the nega-
tive output, both converters turn off and the FLT flag
asserts low. The converters then remain off until the
device is reinitialized by resetting the controller.
When SEQ = 0, power-on sequence can be indepen-
dently controlled by ONINV and ONBST. When SEQ =
0 and ONINV and ONBST are pulled high, both outputs
reach regulation simultaneously. The inverter is held off
while the step-up True-Shutdown switch slowly turns on
to pull PVP to V . The positive output rises to a diode
CC
drop below V . Once the step-up output reaches this
CC
voltage, the step-up and the inverter then ramp their
respective references over a period of 7ms. This brings
the two outputs into regulation at approximately the
same time.
The MAX8614A/MAX8614B also have thermal shutdown.
When the device temperature reaches +170°C (typ) the
device shuts down. When it cools down by 20°C (typ),
the converters turn on.
When SEQ = 1 and ONBST and ONINV are pulled high,
the step-up output powers on first. The inverter is held
off until the step-up completes its entire soft-start cycle
and the positive output is in regulation. Then the invert-
er starts its soft-start cycle and achieves regulation in
about 7ms.
Enable (ONBST/ONINV)
Applying a high logic-level signal to ONBST/ONINV
turns on the converters using the soft-start and power-
on sequencing described below. Pulling ONBST/
ONINV low puts the IC in shutdown mode, turning off
the internal circuitry. When ONBST/ONINV goes high
(or if power is applied with ONBST/ONINV high), the
power-on sequence is set by SEQ. In shutdown, the
device consumes only 0.1µA and both output loads are
disconnected from the input supply.
True Shutdown
The MAX8614A/MAX8614B completely disconnect the
loads from the input when in shutdown mode. In most
step-up converters the external rectifying diode and
inductor form a DC current path from the battery to the
output. This can drain the battery even in shutdown if a
load is connected at the step-up converter output. The
MAX8614A/MAX8614B have an internal switch between
Soft-Start and Inrush Current
The step-up converter and inverter in the MAX8614A/
MAX8614B feature soft-start to limit inrush current and
minimize battery loading at startup. This is accom-
plished by ramping the reference voltage at the input of
each error amplifier. The step-up reference is ramped
the input V
and the inductor node, PVP. When this
CC
switch turns off in shutdown there is no DC path from
the input to the output of the step-up converter. This
load disconnect is referred to as “True Shutdown.” At
10 ______________________________________________________________________________________
Dual-Output (+ and -) DC-DC
Converters for CCD
the inverter output, load disconnect is implemented by
turning off the inverter’s internal power switch.
⎛
⎞
V
− V
IMV
− V
FBN
FBN
R3 = R4 ×
⎜
⎟
V
⎝
⎠
REF
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.
where V
= 1.25V and V
= 0V.
REF
FBN
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.
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.
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.
Applications Information
Capacitor Selection
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:
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.
⎛
⎞
V
BST
R1 = R2
−1
⎟
⎜
V
⎝
⎠
FBP
For stability, the positive output filter capacitor, C1,
should satisfy the following:
where V
= 1.01V.
FBP
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:
2
C1 > (6L I
) / ( R D+ V
)
BSTMAX
CS
BST
where R = 0.015 (MAX8614B), and 0.035 (MAX8614A).
CS
D+ is 1 minus the step-up switch duty cycle and is:
D+ = V
/ V
BST
CC
______________________________________________________________________________________ 11
Dual-Output (+ and -) DC-DC
Converters for CCD
Table 1. Inductor Selection Guide
OUTPUT VOLTAGES
AND LOAD CURRENT
INDUCTOR
L (µH)
DCR (mΩ)
I
(A)
SIZE (mm)
SAT
TOKO
DB3018C, 1069AS-2R0
2.0
4.3
4.3
4.7
10
72
126
47
1.4
3 x 3 x 1.8
3 x 3 x 1.8
TOKO
DB3018C, 1069AS-4R3
0.97
1.2
1
TOKO
S1024AS-4R3M
15V, 50mA
-7.5V, 100mA
4 x 4 x 1.7
Sumida
CDRH2D14-4R7
170
100
3.2 x 3.2 x 1.55
4 x 4 x 1.7
TOKO
S1024AS-100M
0.8
Sumida
CDRH2D11-100
10
10
10
400
295
300
0.35
0.46
0.45
3.2 x 3.2 x 1.2
3.2 x 3.2 x 1.55
3.2 x 2.5 x 2
15V, 20mA
-7.5V, 40mA
Sumida
CDRH2D14-100
Murata
LQH32CN100K33
D- = V
/ V
INV
CC
Table 2. Component Suppliers
Table 2 lists representative low-ESR capacitor suppliers.
SUPPLIER
INDUCTORS
Murata
PHONE
WEBSITE
Input Bypass Capacitor
Although the output current of many MAX8614A/
MAX8614B applications may be relatively small, the
input must be designed to withstand current transients
equal to the inductor current limit. The input bypass
capacitor reduces the peak currents drawn from the
voltage source, and reduces noise caused by the
MAX8614A/MAX8614B switching action. The input
source impedance determines the size of the capacitor
required at the input. As with the output filter capacitor,
a low-ESR capacitor is recommended. A 4.7µF, low-
ESR capacitor is adequate for most applications,
although smaller bypass capacitors may also be
acceptable with low-impedance sources or if the source
770-436-1300 www.murata.com
847-545-600 www.sumida.com
847-297-0070 www.tokoam.com
Sumida
TOKO
DIODES
Central
Semiconductor
(CMHSH5-2L)
631-435-1110 www.centralsemi.com
602-303-5454 www.motorola.com
Motorola
(MBR0540L)
CAPACITORS
Taiyo Yuden
TDK
408-573-4150 www.t-yuden.com
888-835-6646 www.TDK.com
supply is already well filtered. Bypass AV
separately
CC
from V
with a 0.1µF ceramic capacitor placed as
CC
close as possible to the AV
and GND pins.
CC
For stability, the inverter output filter capacitor, C2,
should satisfy the following:
PC Board Layout and Routing
Proper PC board layout is essential due to high-current
levels and fast-switching waveforms that radiate noise.
Breadboards or protoboards should never be used
when prototyping switching regulators.
C2 > (6L V
I
) /
REF INVMAX
(R D- (V
- V ) V
)
CS
REF
INV INV
where R
= 0.0175 (MAX8614B), and 0.040
CS
(MAX8614A). D- is 1 minus the inverter switch duty cycle
and is:
12 ______________________________________________________________________________________
Dual-Output (+ and -) DC-DC
Converters for CCD
V
BATT
(2.7V ~ 5V)
C4
4.7µF
V
INV
13
D2
CMHSH5-21
V
CC
14
1
9
R3
187kΩ
1%
V
INV
ONBST
ONINV
LXN
-7.5V AT 100mA
C2
4.7µF
2
FBN
L2
4.7µH
R4
30.9kΩ
1%
MAX8614A
MAX8614B
REF
3
AV
CC
12
10
C5
0.1µF
4
PVP
LXP
REF
FLT
FBP
C3
1µF
C6
0.22µF
V
BATT
L1
2.2µH
D1
R5
100kΩ
CMHSH5-21
V
BST
6
7
+15V AT 50mA
C1
2.2µF
FAULT
V
BST
R1
1.4MΩ
1%
8
SEQ
R2
100kΩ
1%
GND
PGND
11
5
Figure 1. Typical Application Circuit
It is important to connect the GND pin, the input
bypass-capacitor ground lead, and the output filter
capacitor ground lead to a single point (star ground
configuration) to minimize ground noise and improve
regulation. Also, minimize lead lengths to reduce stray
capacitance, trace resistance, and radiated noise, with
preference given to the feedback circuit, the ground
circuit, and LX_. Place feedback resistors R1–R4 as
close to their respective feedback pins as possible.
Place the input bypass capacitor as close as possible
to AV
and GND.
CC
Chip Information
PROCESS: BiCMOS
______________________________________________________________________________________ 13
Dual-Output (+ and -) DC-DC
Converters for CCD
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
D2
D
A2
PIN 1 ID
N
0.35x0.35
b
[(N/2)-1] x e
REF.
PIN 1
INDEX
AREA
E
E2
DETAIL A
e
A1
k
C
C
L
L
A
L
L
e
e
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
1
-DRAWING NOT TO SCALE-
21-0137
G
2
14 ______________________________________________________________________________________
Dual-Output (+ and -) DC-DC
Converters for CCD
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
COMMON DIMENSIONS
SYMBOL
MIN.
0.70
2.90
2.90
0.00
0.20
MAX.
0.80
3.10
3.10
0.05
0.40
A
D
E
A1
L
k
0.25 MIN.
0.20 REF.
A2
PACKAGE VARIATIONS
DOWNBONDS
ALLOWED
PKG. CODE
T633-1
N
6
D2
E2
e
JEDEC SPEC
MO229 / WEEA
MO229 / WEEA
MO229 / WEEC
MO229 / WEEC
MO229 / WEEC
b
[(N/2)-1] x e
1.90 REF
1.90 REF
1.95 REF
1.95 REF
1.95 REF
2.00 REF
2.40 REF
2.40 REF
1.50±0.10 2.30±0.10 0.95 BSC
1.50±0.10 2.30±0.10 0.95 BSC
1.50±0.10 2.30±0.10 0.65 BSC
1.50±0.10 2.30±0.10 0.65 BSC
1.50±0.10 2.30±0.10 0.65 BSC
0.40±0.05
0.40±0.05
0.30±0.05
0.30±0.05
0.30±0.05
NO
NO
T633-2
6
T833-1
8
NO
T833-2
8
NO
T833-3
8
YES
NO
T1033-1
T1433-1
T1433-2
10
14
14
1.50±0.10 2.30±0.10 0.50 BSC MO229 / WEED-3 0.25±0.05
1.70±0.10 2.30±0.10 0.40 BSC
1.70±0.10 2.30±0.10 0.40 BSC
- - - -
- - - -
0.20±0.05
0.20±0.05
YES
NO
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
2
-DRAWING NOT TO SCALE-
21-0137
G
2
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15
© 2006 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
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