MAX8515EXK+T [MAXIM]
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| 型号： | MAX8515EXK+T |
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MAXIM INTEGRATED PRODUCTS |
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19-2528; Rev 1; 2/03
Wide-Input 0.6V Shunt Regulators for
Isolated DC-to-DC Converters
General Description
Features
The MAX8515A/MAX8515 shunt regulators simplify the
design of voltage regulation and overvoltage protection
(OVP) functions in high-accuracy isolated DC-to-DC con-
verters with output voltages as low as 0.6V. The devices
have supply voltage and feedback inputs separated from
the output shunt stage, and can operate directly from the
DC-to-DC converter output stage when the output voltage
is 1.8V to 18V. Alternately, the MAX8515A/MAX8515 input
stage can be biased from an unregulated 1.7V to 28V
supply, independent of DC-to-DC converter output volt-
age. The MAX8515A/MAX8515 shunts 20mA when the
output voltage is as low as 0.2V.
ꢀ MAX8515A
0.6V 0.5% Initial Accuracy at +25°C
0.6V 1% Accuracy from -40°C to +85°C
ꢀ MAX8515
0.6V 1% Initial Accuracy at +25°C
0.6V 1.8% Accuracy from -40°C to +85°C
ꢀ Sinks 20mA at 0.2V to 18V
ꢀ Input Voltage Range from 1.7V to 28V
ꢀ Directly Drives Optocouplers
ꢀ 0.2Ω Dynamic Output Impedance
ꢀ Space-Saving 5-Pin SC70 or SOT23 Packages
The MAX8515A features an initial output accuracy of
0.5% at +25°C and 1% from -40°C to +85°C and provides
the output voltage regulation function for isolated DC-to-
DC converters. The MAX8515 features initial output
accuracy of 1% at +25°C and 1.8% from -40°C to +85°C
and can provide an output OVP function for isolated DC-
to-DC converters. High open-loop bandwidth allows
design of high-bandwidth DC-to-DC converters.
Ordering Information
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
MAX8515AEXK-T
MAX8515AEZK-T
MAX8515EXK-T
MAX8515EZK-T
5 SC70-5
Low-cost, low-dropout linear regulators can be designed
with the MAX8515A/MAX8515 and an external NPN tran-
sistor for cost-conscious applications that do not require
overcurrent, short-circuit, or overtemperature protection.
5 Thin SOT23-5
5 SC70-5
5 Thin SOT23-5
The MAX8515/MAX8515A are available in space-saving
5-pin SC70 and SOT23 packages and are specified over
the -40°C to +85°C extended temperature range. An eval-
uation kit is available to speed designs.
Functional Diagram appears at end of data sheet.
Selector Guide appears at end of data sheet.
Applications
Isolated DC-to-DC Converters
Network, Telecom, and Cellular Base Station
Power Supplies
Typical Operating Circuit
Low-Dropout Linear Regulators
Shunt Regulator
INPUT SUPPLY
INPUT
1.7V TO 28V 1.7V TO 18V
Adjustable Voltage Reference
PRIMARY SIDE
PWM CONVERTER
CONTROL
Pin Configuration
VOLTAGE
TOP VIEW
IN
OUT
FB
PGND
GND
OUT
1
2
3
5
4
FB
IN
MAX8515A
MAX8515
MAX8515A
MAX8515
ISOLATED DC-DC
CONVERTER
OUTPUT
(DOWN TO 0.6V)
PGND
GND
x
SC7O/THIN SOT23
________________________________________________________________ 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.
Wide-Input 0.6V Shunt Regulators for
Isolated DC-to-DC Converters
ABSOLUTE MAXIMUM RATINGS
IN to GND...............................................................-0.3V to +30V
OUT to GND ...........................................................-0.3V to +20V
FB to GND .................-0.3V to the lower of 5.5V and (V +0.3V)
PGND to GND .......................................................-0.3V to +0.3V
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature Range............................-40°C to +150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
IN
Continuous Power Dissipation (T =+70°C)
A
5-Pin SC70 (derate 3.1mW/°C above +70°C)...........246.9mW
5-Pin Thin SOT23 (derate 9.1mW/°C above +70°C)....727mW
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 = 3.3V, OUT = FB, I
= 5mA, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
IN
OUT
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
IN
IN Voltage Range
IN Supply Current
FB
V
1.7
28
1
V
IN
I
I
= 0.3mA
= 10mA
0.5
2.5
OUT
I
IN
V
= 2V to 28V
mA
IN
4
OUT
MAX8515AE_K
MAX8515E_K
MAX8515AE_K
MAX8515E_K
MAX8515AE_K
MAX8515E_K
0.597
0.594
0.595
0.592
0.594
0.589
0.6
0.6
0.6
0.6
0.6
0.6
3.8
0.2
0.603
0.606
0.605
0.608
0.606
0.608
6
T
T
T
= +25°C
A
A
FB Threshold Accuracy
= 0°C to +85°C
= -40°C to +85°C
V
A
FB Load Regulation
FB Line Regulation
I
= 1mA to 20mA
= 2V to 28V
mV
mV
OUT
V
V
V
V
1
IN
= 1.7V to 28V
1.5
IN
FB Output Voltage Regulation
FB Input Bias Current
OUT
= 0.2V to 18V, I
= 1mA
0.2
1
mV
µA
OUT
OUT
I
= 28V
-0.1
0.02
+0.1
FB(BIAS)
IN
OUT Voltage Range
Maximum Output Current
V
0.2
20
18
0.1
V
OUT
I
V
= 0.2V, V = 2V, V = 0.63V
mA
OUT(MAX)
OUT
IN
FB
T
T
= +25°C
= +85°C
0.001
0.03
0.2
A
A
V
V
= 28V, V
= 0V
= 18V,
OUT
IN
Output Leakage Current
I
µA
OUT(LEAK)
FB
Dynamic Output Impedance
Z
I
= 1mA to 20mA, f <1kHz
0.32
Ω
OUT
OUT
Note 1: Devices are production tested at T = +25°C, limits over temperature are guaranteed by design.
A
2
_______________________________________________________________________________________
Wide-Input 0.6V Shunt Regulators for
Isolated DC-to-DC Converters
Typical Operating Characteristics
(V = 3.3V, I
IN
= 5mA, FB = OUT, circuit in Figure 1, C1 = 0.1µF, C2 = 1µF, T = +25°C, unless otherwise specified.)
A
OUT
GAIN AND PHASE vs. FREQUENCY
= 0.6V
FB BIAS CURRENT
vs. TEMPERATURE
OUT-LEAKAGE CURRENT
vs. TEMPERATURE
V
OUT
MAX8515 toc03
70
70
45
0
-5
40
35
30
25
20
15
10
5
V
V
= 28V
= 18V
FB = GND
IN
OUT
60
50
40
30
20
10
0
V
= 3.3V
IN
-10
-15
-20
-25
-30
0
V
= 10V
IN
-45
-90
V
= 28V
60
IN
-10
-135
-180
FIGURE 2
1
-20
-30
0
-5
0.1
10
FREQUENCY (kHz)
100
1000
-40
-15
10
35
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
GAIN AND PHASE vs. FREQUENCY
= 6V
V
OUTPUT VOLTAGE SLEW RATE
OUT
MAX8515 toc04
MAX8515 toc05
40
30
90
45
V
: 2V/div
OUT
20
0
10
0
-45
-90
0.66V
0.55V
-10
-20
V
: 200mV/div
FB
-135
-180
FIGURE 2
C2 = OPEN
-30
0.1
1
10
FREQUENCY (kHz)
100
1000
2µs/div
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
SUPPLY CURRENT vs. LOAD CURRENT
10
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
T
= +25°C
A
0
-10
-20
-30
-40
-50
-60
-70
-80
V
= 3.3V
IN
T
= +85°C
A
V
= 10V
IN
V
= 28V
IN
T
= +25°C
A
T
= -40°C
A
0.1
1
10
100
1k
10k
0
5
10
LOAD CURRENT (mA)
15
20
FREQUENCY (Hz)
_______________________________________________________________________________________
3
Wide-Input 0.6V Shunt Regulators for
Isolated DC-to-DC Converters
Typical Operating Characteristics (continued)
(V = 3.3V, I
IN
= 5mA, FB = OUT, circuit in Figure 1, C1 = 0.1µF, C2 = 1µF, T = +25°C, unless otherwise specified.)
A
OUT
OUTPUT VOLTAGE CHANGE
vs. LOAD CURRENT
OUTPUT VOLTAGE CHANGE
vs. INPUT VOLTAGE
0.6
0.5
0.4
0.3
0.2
0.1
0
0.05
0.04
0.03
0.02
0.01
0
-0.1
-0.2
-0.3
-0.01
0
5
10
15
20
3
8
13
18
23
28
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
Pin Description
PIN
1
NAME
PGND
GND
OUT
IN
FUNCTION
Power Ground. Connect PGND and GND together.
Analog Ground. Connect GND and PGND together.
2
3
Output. Connect a ceramic capacitor from OUT to GND. See the Applications Information section.
Supply Input. Connect a 0.1µF capacitor to GND.
4
5
FB
Feedback Input. Regulates to 600mV.
when the output voltage is 0.6V. A resistor-divider con-
Detailed Description
nected from OUT to GND produces higher output volt-
ages and allows for a smaller output capacitor. The
value of the output capacitor is inversely proportional to
the output voltage:
The MAX8515A/MAX8515 adjustable shunt regulators
feature isolated supply inputs and outputs, ideal for isolat-
ed power-supply applications using an optocoupler in the
feedback path. The MAX8515A/MAX8515 sink 20mA with
V
at 0.2V. The wide input supply range allows the
OUT
R1
R2
VOUT = 0.6 × 1 +
device to operate from 1.7V to 28V. The MAX8515A/
MAX8515 compare the FB input to a precision 600mV
reference. If the FB input is low, OUT sinks no current. If
FB rises above 600mV, OUT sinks up to 20mA.
0.6
COUT =1µF ×
V
OUT
Applications Information
Set the current limit with a resistor connected from IN to
OUT. This type of shunt regulator is limited to low-current
applications. The MAX8515A/MAX8515 can typically sink
up to 20mA in this application.
Shunt Regulator/Adjustable
Voltage Reference
Figure 1 shows the MAX8515A/MAX8515 configured as a
shunt regulator. Connect FB to OUT for an output voltage
of 0.6V. Connect a 1.0µF capacitor from OUT to GND
Figure 2 shows the test circuits for gain and phase plots.
4
_______________________________________________________________________________________
Wide-Input 0.6V Shunt Regulators for
Isolated DC-to-DC Converters
5.6V
V
IN
1.8V
R3
3.3V
V
1kΩ
OUT
0.6V/20mA
TEST
2.2nF
V
= 0.6V
1MΩ
OUT
TEST CIRCUIT
R1 = SHORT
R2 = OPEN
IN
OUT
C1
0.1µF
C2
1.0µF
IN
OUT
MAX8515A
MAX8515
R1
R2
0.82µF
50kΩ
0.1µF
V
(V) R3 (Ω)
IN
MAX8515A
MAX8515
PGND
GND
3.3
10
28
135
470
FB
PGND
GND
1.33k
NETWORK
FB
ANALYZER
SOURCE
2.2nF
REFERENCE
1MΩ
Figure 1. MAX8515A/MAX8515 Typical Application Circuit,
Shunt Regulator/Adjustable Voltage Reference
GAIN = TEST/REFERENCE
11V
Optical Feedback
Setting V
OUT
115kΩ
TEST
Figure 3 displays an application circuit using the
MAX8515A/MAX8515 in an opto-isolated feedback cir-
cuit. The maximum bias current for the photodiode is
set with R1. The isolated DC-to-DC converter compen-
sation circuit is formed with R2, C3, and C4. Resistors
R3 and R4 set the isolated DC-to-DC converter output
voltage. C1 decouples the input supply and C2 is
needed to stabilize the MAX8515A/MAX8515. Calculate
1%
2.2nF
1MΩ
3.3V
V
= 6V
OUT
TEST CIRCUIT
160kΩ
IN
OUT
0.1µF
0.1µF
MAX8515A
MAX8515
50kΩ
V
REG
with the following equation:
90.1kΩ
1%
NETWORK
ANALYZER
SOURCE
PGND
GND
R3
R4
FB
VREG = 0.6 × 1 +
2.2nF
REFERENCE
Set R4 to 10kΩ and calculate R3 by:
10kΩ
1%
1MΩ
V
V
OUT
GAIN = TEST/REFERENCE
R3 =
-1 × R4
FB
Figure 2. Test Circuits for Gain and Phase Plots
For example, given a regulator output voltage of 1.8V
and R4 = 10kΩ, R3 is found to be 20kΩ.
The midband gain is given by:
Compensation Circuit
A typical compensation scheme is depicted in Figure 3.
C3 provides an integrator function that minimizes out-
put regulation error.
R2
R3
A =
Add C4 for high-frequency noise rejection. Determine
R2 based on the midband gain required by the isolated
R2 provides additional phase compensation at the zero
frequency f :
z
power supply. Choose f based on the power supply
z
1
small-signal transfer function. Calculate C3 once f
is known.
z
fZ
=
2π × R2 × C3
_______________________________________________________________________________________
5
Wide-Input 0.6V Shunt Regulators for
Isolated DC-to-DC Converters
Overvoltage Protection
V
REG
1.8V
INPUT
SUPPLY
Figure 4 shows an isolated OVP circuit. R1 limits the
current supplied to the photodiode. R2 limits the
MAX8515A/MAX8515 input current. R3 and R4 set the
trip threshold for the OVP. C1 is the input supply
decoupling capacitor.
V+
MAX5003
NDRV
Values for R3 and R4 are chosen based on the needed
OVP threshold. For example, a trip threshold of 25%
above the rated output voltage is needed for an OVP
circuit. The values of R3 can be determined from the
following equation once R4 is chosen; 10kΩ is recom-
mended for R4. Then, R3 = 6.2kΩ.
PGND
CON
R1
47kΩ
VOVP
VFB
R3 =
- 1 × R4
IN
OUT
FB
R2
C2
0.1µF
R3
20kΩ
1%
C1
0.1µF
C4
MAX8515A
MAX8515
where V
= 0.8V x 1.25 for the given example.
OVP
C3
PGND
GND
Linear Regulator
Use an external pass transistor in conjunction with the
MAX8515A/MAX8515 to create a linear regulator as
shown in Figure 5. Determine the output voltage of the
regulator by:
R4
10kΩ
1%
R2
R3
VREG = 0.6V × 1 +
Figure 3. MAX8515A/MAX8515 Typical Application Circuit,
Opto-Feedback Circuit
Choose R1 to maintain load regulation up to a 2A load.
Use the following equation:
6V TO 10V
V
- VREG - VBE
IN_MIN
R1
1.2kΩ
R1 =
× β
IO_MAX
FEEDBACK
OPTOCOUPLER
where I
is the rated maximum output current,
O_MAX
R2
which is 2A in this application circuit. V
is the output
2kΩ
DC-DC OUTPUT
0.8V
REG
voltage of the linear regulator. V is the base-to-emitter
BE
forward voltage of Q1, and β is the minimum current gain
IN
OUT
FB
of Q1 at rated load current. V is the minimum input volt-
IN
C1
0.1µF
16V
R3
6.2kΩ
1%
age at IN. For the typical application circuit, V
2.375V, V
=
MAX8515A
MAX8515
IN_MIN
= 1.0V, V = 0.65V, and β = 180. Choose
REG
BE
PGND
GND
R1 = 15Ω for fast transient response. C1 is the input
decoupling capacitor and C2 is the compensation
capacitor. Use a 1µF, 6.3V capacitor for this application.
Figure 6 shows a typical load-regulation curve for the cir-
cuit in Figure 5. This circuit does not provide short-circuit,
overcurrent, or overtemperature protection.
R4
10kΩ
1%
Figure 4. MAX8515A/MAX8515 Typical Application Circuit,
OVP Circuit (Set to 1V OVP Threshold for 0.8V Nominal Output)
6
_______________________________________________________________________________________
Wide-Input 0.6V Shunt Regulators for
Isolated DC-to-DC Converters
Functional Diagram
I
O
Q1
FZT1049A
2A (MAX)
V
CC
1.2V TO
V
REG
1V
2.5V
OUT
IN
0.6V
REFERENCE
MAX8515A
MAX8515
R1
V
IN
IN
OUT
FB
FB
R2
6.65kΩ
C1
0.1µF
C2
1.0µF
MAX8515A
MAX8515
PGND
GND
GND
R3
10kΩ
Selector Guide
V
(V) R1 (Ω)
PART
INITIAL ACCURACY
TOP MARKS
ADX
IN
2.5
3.3
5
22.1
40.2
82.5
MAX8515AEXK-T
MAX8515AEZK-T
MAX8515EXK-T
MAX8515EZK-T
0.6V, 0.5% feedback
0.6V, 0.5% feedback
0.6V, 1% feedback
0.6V, 1% feedback
ADRK
ADY
ADRL
Figure 5. MAX8515A/MAX8515 Typical Application Circuit,
Linear Regulator
Chip Information
TRANSISTOR COUNT: 50
PROCESS: BiCMOS
LINEAR-REGULATOR
LOAD REGULATION
0
-0.5
V
= 2.5V
CC
-1.0
-1.5
-2.0
-2.5
-3.0
-3.5
-4.0
V
= 1.2V
CC
C
= 220µF
VCC
-4.5
-5.0
0
0.5
1.0
LOAD CURRENT (A)
1.5
2.0
Figure 6. Load Regulation of Linear-Regulator Circuit
_______________________________________________________________________________________
7
Wide-Input 0.6V Shunt Regulators for
Isolated DC-to-DC Converters
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.)
8
_______________________________________________________________________________________
Wide-Input 0.6V Shunt Regulators for
Isolated DC-to-DC Converters
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.)
_______________________________________________________________________________________
9
Wide-Input 0.6V Shunt Regulators for
Isolated DC-to-DC Converters
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.)
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.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2003 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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