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LT3571EUD#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
LT3571
1
3571fa
TYPICAL APPLICATION
DESCRIPTION
75V DC/DC Converter
for APD Bias
The LT
®
3571 is a current mode step-up DC/DC converter
designed to bias avalanche photodiodes (APDs) in optical
receivers with an output voltage up to 75V. The LT3571
features a high side fi xed voltage drop APD current moni-
tor with better than 10% relative accuracy over the entire
temperature range. The integrated power switch, Schottky
diode and APD current monitor allow a small solution
footprint and low solution cost. It combines a traditional
voltage loop and a unique current loop to operate as
a constant-current source or constant-voltage source.
The inductor-based topology ensures an input free from
switching noise. The integrated high side current monitor
produces a current proportional to the APD current with
better than 10% relative accuracy over four decades of
dynamic range in the input range of 250nA to 2.5mA. This
current can be used as a reference to provide a digitally
programmed output voltage via the CTRL pin. The LT3571
is available in the tiny footprint (3mm × 3mm) 16-lead
QFN package.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
45V Low Noise APD Bias Power Supply
FEATURES
APPLICATIONS
n
High APD Voltage: Up to 70V
n
Integrated Schottky Diode
n
75V, 370mA Internal Switch
n
High Side Fixed Voltage Drop APD Current Monitor
n
Adjustable Frequency: 250kHz to 2MHz
n
Frequency Synchronization
n
Wide V
IN
Range: 2.7V to 20V
n
Constant-Voltage and Constant-Current Regulation
n
Programmable Current Limit Protection
n
Surface Mount Components
n
Low Shutdown Current <1µA
n
Internal Soft-Start
n
Internal Compensation
n
CTRL Pin Allows Output Adjustment with
No Polarity Inversion
n
3mm × 3mm 16-Lead QFN Package
n
APD Bias
n
PIN Diode Bias
n
Optical Receivers and Modules
n
Fiber Optic Network Equipment
APD Bias Ripple
1µF
MONIN
V
REF
R
T
SHDN
CTRL
GND
SYNC
V
OUT
FB
V
IN
SW
LT3571
MON APD
OFF ON
V
IN
5V
20.5k
49.9
45V
12.1k
1MHz
3571 TA01a
0.1µF
10k
10nF
50V
0.1µF
10µH
1M
20
10nF
I
APD
= 1mA 500ns/DIV
3571 TA01b
500µV/DIV
LT3571
2
3571fa
PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS
Input Voltage (V
IN
), SHDN ........................................20V
V
OUT
, MONIN, APD ....................................................75V
MON ..........................................................................12V
SW ............................................................................75V
CTRL, FB, SYNC ..........................................................5V
R
T
, V
REF
...................................................................1.5V
Operating Ambient Temperature Range
(Note 2) .............................................–40°C to 125°C
Operating Junction Temperature
(Note 2) .............................................–40°C to 125°C
Storage Temperature Range ...................–65°C to 150°C
(Note 1)
16
17
15 14 13
5 6 7 8
TOP VIEW
UD PACKAGE
16-LEAD (3mm s 3mm) PLASTIC QFN
9
10
11
12
4
3
2
1NC
APD
MONIN
V
OUT
SHDN
V
IN
GND
R
T
MON
FB
CTRL
V
REF
SW
SW
GND
SYNC
T
JMAX
= 125°C, θ
JA
= 68°C/W, θ
JC
= 4.2°C/W (NOTE 2)
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Operating Voltage 2.7 V
Maximum Operating Voltage 20 V
Supply Current V
FB
= 1.3V, Not Switching
V
SHDN
= 0V
1.7
0.1
2.2
0.5
mA
µA
Feedback Voltage V
CTRL
= 1.25V, V
OUT
= V
MONIN
l
0.985
0.97
1 1.015
1.03
V
V
Feedback Line Regulation 2.7V < V
IN
< 20V 0.03 0.07 %/V
Current Sense Voltage (V
OUT
– V
MONIN
)V
OUT
= 30V
l
185 200 215 mV
FB Pin Bias Current V
FB
= 0V
l
60 100 nA
V
REF
Pin Voltage I
REF
= –100µA
l
1.200 1.222 1.240 V
V
REF
Pin Line Regulation 2.7V < V
IN
< 20V 0.03 0.07 %V
R
T
Voltage 1V
SYNC Resistance to GND V
SYNC
= 2V 45 k
SYNC Input Low 0.4 V
SYNC Input High
1.5 V
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3571EUD#PBF LT3571EUD#TRPBF LDTN
16-Lead (3mm × 3mm) Plastic QFN
–40°C to 125°C
LT3571IUD#PBF LT3571IUD#TRPBF LDTN
16-Lead (3mm × 3mm) Plastic QFN
–40°C to 125°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to:
http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C, V
IN
= 3V, V
SHDN
= 3V, unless otherwise noted.
LT3571
3
3571fa
ELECTRICAL CHARACTERISTICS
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C, V
IN
= 3V, V
SHDN
= 3V, unless otherwise noted.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Switching Frequency R
T
= 12.1k
R
T
= 4.22k
R
T
= 56.2k
l
0.85
1.7
210
1
2
250
1.15
2.3
280
MHz
MHz
kHz
Maximum Duty Cycle R
T
= 56.2k (250kHz)
SYNC = 300kHz Clock Signal, R
T
= 56.2k
R
T
= 12.1k (1MHz)
R
T
= 4.22k (2MHz)
l
95
92
85
75
97
96
90
80
%
%
%
%
Switch Current Limit 370 470 570 mA
Switch V
CESAT
I
SW
= 200mA 240 mV
Switch Leakage Current V
SW
= 75V 2 µA
Schottky Forward Voltage I
SCHOTTKY
= 200mA 850 mV
Schottky Reverse Leakage V
OUT
– V
SW
= 75V 5 µA
SHDN Voltage High 1.5 V
SHDN Voltage Low 0.4 V
SHDN Pin Bias Current 50 65 µA
CTRL to FB Offset V
CTRL
= 0.5V
l
–5
–10
5
5
15
20
mV
mV
CTRL Input Bias Current Current Out of Pin, V
CTRL
= 0.5V 20 100 nA
APD Current Monitor Gain 250nA ≤ I
APD
< 10µA, 10V < V
MONIN
< 75V
10µA ≤ I
APD
≤ 2.5mA, 20V < V
MONIN
< 75V
l
l
0.185
0.194
0.20
0.20
0.215
0.206
Monitor Output Voltage Clamp 11.5 V
APD Monitor Voltage Drop V
MONIN
– V
APD,
I
APD
= 1mA
l
4.8 5 5.2 V
MONIN Pin Current Limit V
MONIN
= 40V, V
APD
= 0V 30 mA
Note 2: The LT3571E is guaranteed to meet specifi ed performance from
0°C to 125°C junction temperature. Specifi cations over the –40°C to
125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT3571I is guaranteed to meet performance specifi cations over the –40°C
to 125°C operating junction temperature range.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16

LT3571EUD#TRPBF

Mfr. #:
Buy LT3571EUD#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 75V DC/DC Conv for APD Bias
Lifecycle:
New from this manufacturer.
Delivery:
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