Rainbow Electronics DS1842A User Manual
General Description
The DS1842A integrates the discrete high-voltage
components necessary for avalanche photodiode
(APD) bias and monitor applications. A switch FET and
precision voltage-divider network are used in conjunction with an external DC-DC controller to create a boost
DC-DC converter. A current clamp limits current
through the APD and also features an external shutdown. The precision voltage-divider network is provided for precise control of the APD bias voltage. The
device also includes a dual current mirror to monitor
the APD current.
Applications
APD Biasing
GPON ONU and OLT
Features
♦ 76V Maximum Boost Voltage
♦ Switch FET
♦ Current Monitor with a Wide 1µA to 2mA Range,
Fast 50ns Time Constant, and 10:1 and 5:1 Ratio
♦ 2mA Current Clamp with External Shutdown
♦ Precision Voltage Feedback
♦ Multiple External Filtering Options
♦ 3mm x 3mm, 14-Pin TDFN Package with Exposed Pad
DS1842A
76V, APD, Bias Output Stage with
Current Monitoring
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
19-4994; Rev 0; 10/09
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
EVALUATION KIT
AVAILABLE
PART TEMP RANGE PIN-PACKAGE
DS1842AN + -40°C to +85°C 14 TDFN-EP*
DS1842AN +T& R -40°C to +85°C 14 TDFN-EP*
+
Denotes a lead(Pb)-free/RoHS-compliant package.
T&R = Tape and reel.
*
EP = Exposed pad.
DS1875
DS1842A
SW
FB
D2
COMP
MON3
LX
GATE
PGND
FBOUT
R
1
R
2
MIRIN
FBIN
MIR1
CLAMP
NOTE: SEE THE LAYOUT CONSIDERATIONS SECTION.
MIROUTGNDEP
3.3V
CURRENT MIRROR
CURRENT
LIMIT
MIR2
C
BULK
C
COMP
R
COMP
EXTERNAL MONITOR
TIA
APD
ROSA
Typical Application Circuit
DS1842A
76V, APD, Bias Output Stage with
Current Monitoring
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(TA= -40°C to +85°C, unless otherwise noted.)
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.
Note 1: Rising MIROUT transition from 10µA to 1mA; V
MIRIN
= 40V, 2.5kΩ load.
Note 2: Not production tested. Guaranteed by design.
Voltage Range on GATE and CLAMP
Relative to GND...................................................-0.3V to +12V
Voltage Range on MIRIN, MIROUT, FBIN
MIR1, and MIR2 Relative to GND........................-0.3V to +80V
Voltage Range on FBOUT Relative to GND ..........-0.3V to +6.0V
Voltage Range on LX Relative to GND...................-0.3V to +85V
Operating Junction Temperature Range...........-40°C to +150°C
Storage Temperature Range .............................-55°C to +135°C
Soldering Temperature ..........................Refer to the IPC JEDEC
J-STD-020 Specification.
Switching Frequenc y f
FET Capacitance
FET Gate Res is tance R
FET On-Res is tance R
GATE Voltage V
Switching Current I
LX Voltage V
LX Leakage I
CLAMP Voltage V
CLAMP Threshold V
Maximum MIROUT Current I
MIR1 to MIROUT Ratio K
MIR2 to MIROUT Ratio K
MIR1, MIR2 Rise Time
(20%/80%)
Shutdown Temperature T
Hysteresis Temperature T
Leakage on GATE and CLAMP IIL -1 +1 μA
Resistor-Divider Ratio (R1/R2) KR TA = +25°C, V
Resistor-Di vider Tempco ±50 ppm/°C
Resistor-Divider End-to-End
Resistance
PARAMETER S YMBOL CONDITIONS MIN TYP MAX UNITS
SW
C
GATE VGS
C
DSON
GS
LX
LX
IL(LX)
CLAMP
CLT
MIROUT
MIR1
MIR2
t
RC
SHDN
HYS
R
RES
0 1.2 MHz
= 0V, V
fSW= 1MHz 90
LX
22
G
V
= 3V, ID= 170mA 1 2
GS
V
= 10V, ID= 170mA 0.75 1.4
GS
0 11 V
Duty cycle = 10%, fSW= 100kHz 680 mA
80 V
V
0 11 V
1.25 1.8 2.35 V
(Note 2) 5 °C
TA = +25°C, V
= 0V, V
GATE
CLAMP = low 1.8 2.75 3.85 mA
CLAMP = high 10 μA
15V < V
MIRIN
15V < V
MIRIN
(Note 1) 30 ns
(Note 2) +150 °C
= 25V 40
DS
= 76V -1 +1 μA
LX
< 76V, I
< 76V, I
= 76V 59.5 60.25
FBIN
= 76V 308 385 481 k
FBIN
> 1μA 0.096 0.100 0.104 A/A
MIROUT
> 1μA 0.192 0.200 0.208 A/A
MIROUT
pF
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