MAX15059BETE+ [MAXIM]
76V, 300mW Boost Converter and Current Monitor for APD Bias Applications; 76V ， 300mW boost转换器和电流监测器，用于APD偏置
| 型号： | MAX15059BETE+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 76V, 300mW Boost Converter and Current Monitor for APD Bias Applications |
| 文件： | 总15页 (文件大小：1985K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-5132; Rev 1; 3/10
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
General Description
Features
S Input Voltage Range: +2.8V to +5.5V
The MAX15059 constant-frequency pulse-width modu-
lating (PWM) step-up DC-DC converter features an
internal switch and a high-side current monitor with high-
speed adjustable current limiting. This device is capable
of generating output voltages up to 76V (300mW for
the MAX15059A and 200mW for the MAX15059B) and
provides current monitoring up to 4mA. The MAX15059
operates from 2.8V to 5.5V.
S Wide Output-Voltage Range from (V + 5V) to 76V
IN
S Internal 1I (typ) 80V MOSFET
S Boost Converter Output Power: 300mW
S 200mW Version Available for Smaller Inductor
S Accurate Q5% (1:1 and 5:1) High-Side Current
Monitor
S Resistor-Adjustable Ultra-Fast APD Current Limit
The constant-frequency (400kHz) current-mode PWM
architecture provides low-noise-output voltage that is
easy to filter. A high-voltage internal power MOSFET
allows this device to boost output voltages up to 76V.
Internal soft-start circuitry limits the input current when
the boost converter starts. The MAX15059 features a
shutdown mode to save power.
(1µs Response Time)
S Open-Drain Current-Limit Indicator Flag
S 400kHz Fixed-Switching Frequency
S Constant PWM Frequency Provides Easy Filtering
in Low-Noise Applications
S Internal Soft-Start
S 2µA (max) Shutdown Current
S -40NC to +85NC Temperature Range
The MAX15059 includes a current monitor with more
than three decades of dynamic range and monitors
current ranging from 500nA to 4mA with high accuracy.
Resistor-adjustable current limiting protects the APD
from optical power transients. A clamp diode protects
the monitor’s output from overvoltage conditions. Other
protection features include cycle-by-cycle current limit-
ing of the boost converter switch, undervoltage lockout
(UVLO), and thermal shutdown if the die temperature
reaches +150NC.
S Small, Thermally Enhanced, 3mm x 3mm, Lead-
Free, 16-Pin TQFN-EP Package
Ordering Information
MAXIMUM
POWER
(mW)
I
:
PIN-
PACKAGE
APD
PART
I
MOUT
MAX15059AETE+
MAX15059BETE+
300
200
1:1
5:1
16 TQFN-EP*
16 TQFN-EP*
The MAX15059 is available in a thermally enhanced,
lead-free, 16-pin TQFN-EP package and operates over
the -40NC to +85NC temperature range.
Note: All devices operate over the -40°C to +85°C temperature
range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Applications
Avalanche Photodiode Biasing and Monitoring
PIN Diode Bias Supply
Typical Operating Circuit
L1
4.7µH
V
= 2.8V
Low-Noise Varactor Diode Bias Supply
FBON Modules
IN
TO 5.5V
D1
V
OUT
(76V MAX)
C
IN
R2
348kI
C
OUT
0.1µF
1µF
GPON Modules
R
ADJ
IN
LX
CNTRL
PGND
R1
6.34kI
BIAS
FB
MAX15059
SHDN
ILIM
GPIO
GPIO
DAC
RLIM
V
DD
V
DD
CLAMP
MOUT
µC
R
LIM
2.87kI
ADC
SGND
APD
C
MOUT
OPTIONAL
(10nF)
R
MOUT
1kI
APD
TIA
_______________________________________________________________ Maxim Integrated Products
1
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.
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
ABSOLUTE MAXIMUM RATINGS
IN, SHDN, FB, ILIM, RLIM, CNTRL to SGND..........-0.3V to +6V
LX to PGND...........................................................-0.3V to +80V
BIAS to SGND ......................................................-0.3V to +79V
Junction-to-Case Thermal Resistance (B ) (Note 1)
16-Pin TQFN-EP ......................................................... +7NC/W
JC
Junction-to-Ambient Thermal Resistance (B ) (Note 1)
JA
APD, CLAMP to SGND...........................-0.3V to (V
+ 0.3V)
16-Pin TQFN-EP ....................................................... +48NC/W
Operating Temperature Range.......................... -40NC to +85NC
Maximum Junction Temperature.....................................+150NC
Storage Temperature Range............................ -65NC to +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
BIAS
PGND to SGND....................................................-0.3V to +0.3V
MOUT to SGND.................................. -0.3V to (V + 0.3V)
CLAMP
Continuous Power Dissipation (T = +70NC)
A
16-Pin TQFN-EP (derate 20.8mW/NC
above +70NC).........................................................1666.7mW
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
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
IN
= V
= 3.3V, C = 1FF, V
= V
= 0V, V = 40V, LX = APD = CLAMP = ILIM = unconnected, V
BIAS MOUT
SHDN
CNTRL
IN
PGND
SGND
= 0V, T = -40NC to +85NC, unless otherwise noted. Typical values are at T = +25NC.) (Note 2)
= VRLIM
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
INPUT SUPPLY
Supply Voltage Range
Supply Current
V
2.8
5.5
1.2
V
IN
I
V
V
= 1.4V, no switching
1
mA
V
SUPPLY
FB
IN
Undervoltage-Lockout Threshold
Undervoltage-Lockout Hysteresis
Shutdown Current
V
rising
2.475
2.6
200
2.775
UVLO
V
I
mV
FA
FA
UVLO_HYS
I
2
V
V
= 0V
SHDN
SHDN
Shutdown BIAS Current
BOOST CONVERTER
20
= 3.3V, V
= 0V
BIAS_SHDN
BIAS
SHDN
Output-Voltage Adjustment
Range
V
IN
+ 5
76
V
Switching Frequency
Maximum Duty Cycle
FB Set-Point Voltage
f
V
V
= 5V
380
88
400
90
420
92
kHz
%
SW
IN
IN
D
= 2.8V
CLK
V
1.2054
1.23
1.2546
500
2
V
FB_SET
FB Input-Bias Current
Internal Switch On-Resistance
I
V
= V
, T = +25NC
nA
I
FB
FB
FB_SET
A
R
I
LX
= 100mA, V = 2.8V
1
ON
IN
MAX15059A
MAX15059B
1.1
1.2
0.9
100
1.3
Peak Switch Current Limit
I
A
LIM_LX
0.825
0.975
Peak Current-Limit Response
LX Leakage Current
Line Regulation
ns
FA
V
LX
= 76V, T = +25NC
1
A
2.8V PV P5.5V, I
= 4.5mA
0.2
1
%
IN
LOAD
Load Regulation
0 PI
P4.5mA
%
LOAD
Soft-Start Duration
8
ms
Steps
Soft-Start Steps
32
CONTROL INPUT (CNTRL)
Maximum Control Input Voltage
Range
FB set point is controlled to V
1.2
V
CNTRL
2
______________________________________________________________________________________
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
ELECTRICAL CHARACTERISTICS (continued)
(V = V
= V
= 3.3V, C = 1FF, V
= V
= 0V, V = 40V, LX = APD = CLAMP = ILIM = unconnected, V
BIAS MOUT
IN
SHDN
CNTRL
IN
PGND
SGND
= 0V, T = -40NC to +85NC, unless otherwise noted. Typical values are at T = +25NC.) (Note 2)
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CNTRL-to-REF Transition
Threshold
V
V
= V
above this voltage
1.3
V
FB
REF
CNTRL Input-Bias Current
CURRENT MONITOR
Bias Voltage Range
= V
, T = +25NC
500
nA
CNTRL
FB_SET
A
V
10
76
250
250
6
V
BIAS
MAX15059A
150
150
4
I
= 500nA
FA
APD
MAX15059B
MAX15059A
MAX15059B
Bias Quiescent Current
I
BIAS
I
I
= 2mA
mA
V
APD
3
4
Voltage Drop
V
R
= 2mA, V
= V
- V
2.7
3.5
DROP
APD
DROP
BIAS
APD
Dynamic Output Resistance at
MOUT
R
= DV
/DI
,
MOUT
MOUT MOUT
MAX15059A
5
GI
MOUT
I
= 2.5mA
APD
APD Current-Step Response
MOUT Output Leakage
Step load on I
= 20FA to 1mA
25
1
ns
APD
nA
V
V
-
MOUT
Output Clamp Voltage
Forward diode current = 500FA
= V = 76V
0.45
0.7
1
0.95
V
nA
V
CLAMP
Output Clamp Leakage Current
MOUT Voltage Range
V
BIAS
CLAMP
10V PV
P76V, 0 PI
P1mA, CLAMP
V
-
BIAS
APD
BIAS
2.7
V
MOUT
is unconnected
MAX15059A
MAX15059B
MAX15059A
MAX15059B
0. 95
0.19
1
1.1
I
I
= 500nA
= 2mA
APD
APD
0.2
1
0.22
Current Gain
I
/I
mA/mA
MOUT APD
0.965
0.193
1.035
0.207
0.2
(DI
/I
)/DV
,
MOUT MOUT
BIAS
MAX15059A
35
35
300
610
700
Power-Supply Rejection Ratio
PSRR
V
= 10V to 76V and I
BIAS APD
ppm/V
MAX15059B
300
4.6
= 5FA to 1mA (Note 3)
APD Input Current Limit
I
4
5.2
5.2
mA
mA
LIM_APD
Current-Limit Adjustment Range
9.75kIRR R0
0.9
LIM
I
settles to within 0.1%,
MOUT
I
I
= 500nA
= 2.5mA
7.5
90
ms
APD
Power-Up Settling Time
t
10nF connected from APD to
ground
S
Fs
APD
LOGIC I/O
V
V
0.8
V
V
SHDN Input Voltage Low
IL
2.1
SHDN Input Voltage High
ILIM Output Voltage Low
IH
V
I
I
= 2mA
LIM
0.1
1
V
OL
T
= +25NC
A
FA
ILIM Output Leakage Current
THERMAL PROTECTION
Thermal-Shutdown Temperature
Thermal-Shutdown Hysteresis
OH
Temperature rising
+150
15
NC
NC
Note 2: All MIN/MAX parameters are tested at T = +25NC. Limits overtemperature are guaranteed by design.
A
Note 3: Guaranteed by design and not production tested.
_______________________________________________________________________________________
3
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Typical Operating Characteristics
(V = 3.3V, V
IN OUT
= 70V, T = +25°C, unless otherwise noted.)
A
MINIMUM STARTUP VOLTAGE
vs. LOAD CURRENT
EFFICIENCY vs. LOAD CURRENT
EFFICIENCY vs. LOAD CURRENT
2.65
2.64
2.63
2.62
2.61
2.60
2.59
2.58
2.57
2.56
2.55
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
V
= 3.3V
V = 5V
IN
IN
V
V
= 30V
= 70V
OUT
OUT
V
V
= 30V
= 70V
OUT
OUT
V
= 50V
OUT
V
= 50V
OUT
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
LOAD CURRENT (mA)
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
LOAD CURRENT (mA)
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
LOAD CURRENT (mA)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
NO-LOAD SUPPLY CURRENT
vs. SUPPLY VOLTAGE
2.0
50
45
40
35
30
25
20
15
10
5
V
= 1.4V
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
FB
T = +25°C
A
T = +85°C
A
T = +85°C
A
T = +25°C
A
T = -40°C
A
T = -40°C
A
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
EXITING SHUTDOWN
ENTERING SHUTDOWN
MAX15059 toc06
MAX15059 toc07
SHDN
2V/div
SHDN
2V/div
INDUCTOR
CURRENT
500mA/div
INDUCTOR
CURRENT
500mA/div
V
OUT
50V/div
V
OUT
50V/div
1ms/div
4ms/div
4
______________________________________________________________________________________
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Typical Operating Characteristics (continued)
(V = 3.3V, V
IN
= 70V, T = +25°C, unless otherwise noted.)
A
OUT
LIGHT-LOAD SWITCHING WAVEFORMS
HEAVY-LOAD SWITCHING WAVEFORMS
WITH RC FILTER
WITH RC FILTER
MAX15059 toc08
MAX15059 toc09
V
V
BIAS
BIAS
(AC-COUPLED)
50mV/div
(AC-COUPLED)
20mV/div
V
V
LX
LX
50V/div
50V/div
I
L
I
L
500mA/div
1A/div
1µs/div
1µs/div
LOAD-TRANSIENT RESPONSE
LINE-TRANSIENT RESPONSE
MAX15059 toc10
MAX15059 toc11
V
IN
2V/div
I
APD
3.3V
2mA/div
0mA
V
BIAS
(AC-COUPLED)
500mV/div
V
BIAS
(AC-COUPLED)
50mV/div
100µs/div
100µs/div
LX LEAKAGE CURRENT
vs. TEMPERATURE
MAXIMUM LOAD CURRENT
vs. SUPPLY VOLTAGE
LOAD REGULATION
10
100
90
80
70
60
50
40
30
20
10
0
0.5
A: V
D: V
= 30V, B: V
= 55V, E: V
= 35V, C: V
= 60V, F: V
= 45V,
= 70V
CURRENT INTO LX PINS
= 70V
OUT
OUT
OUT
OUT
OUT
OUT
9
8
7
6
5
4
3
2
1
0
0.4
0.3
V
LX
0.2
A
0.1
B
C
0
-0.1
-0.2
-0.3
-0.4
-0.5
D
E
F
-40
-15
10
35
60
85
2.5
3.0
3.5
4.0
4.5
5.0
5.5
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
LOAD CURRENT (mA)
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Typical Operating Characteristics (continued)
(V = 3.3V, V
IN OUT
= 70V, T = +25°C, unless otherwise noted.)
A
BIAS CURRENT vs. BIAS VOLTAGE
BIAS CURRENT vs. APD CURRENT
BIAS CURRENT vs. TEMPERATURE
10
1
10
1
10
I
= 2mA
APD
I
= 2mA
APD
1
0.1
0.01
0.1
I
= 500nA
APD
I
= 500nA
APD
V
= 70V
BIAS
0.01
0.1
0
10 20 30 40 50 60 70 80
BIAS VOLTAGE (V)
0.0001 0.001
0.01
0.1
1
10
-40
-15
10
35
60
85
APD CURRENT (mA)
TEMPERATURE (°C)
GAIN ERROR vs. APD CURRENT
GAIN ERROR vs. APD CURRENT
GAIN ERROR vs. TEMPERATURE
5
4
5
4
2.0
1.6
V
= 70V
BIAS
I
= 0.5µA
APD
3
3
1.2
I
= 5µA
APD
I
= 50µA
APD
2
2
0.8
1
1
0.4
0
0
0
I
= 500µA
APD
-1
-2
-3
-4
-5
-1
-2
-3
-4
-5
-0.4
-0.8
-1.2
-1.6
-2.0
I
= 2mA
APD
V
= 70V
BIAS
0.1
1
10
I
100
(µA)
1000 10,000
0.1
1
10
I
100
(µA)
1000 10,000
-40
-15
10
35
60
85
TEMPERATURE (°C)
APD
APD
GAIN ERROR vs. BIAS VOLTAGE
GAIN ERROR vs. TEMPERATURE
2.0
1.6
2.0
1.6
1.2
I
= 50µA
APD
1.2
I
= 5µA
APD
I
= 2mA
I
= 0.5µA
APD
APD
0.8
0.8
0.4
0.4
0
0
-0.4
-0.8
-1.2
-1.6
-2.0
-0.4
-0.8
-1.2
-1.6
-2.0
I
= 500µA
I
= 0.5µA
APD
APD
I
= 500µA
APD
I
= 2mA
APD
I
= 50µA
I
= 5µA
APD
APD
10
20
30
40
50
60
70
80
-40
-15
10
35
60
85
BIAS VOLTAGE (V)
TEMPERATURE (°C)
6
______________________________________________________________________________________
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Typical Operating Characteristics (continued)
(V = 3.3V, V
IN OUT
= 70V, T = +25°C, unless otherwise noted.)
A
GAIN ERROR vs. BIAS VOLTAGE
APD TRANSIENT RESPONSE
MAX15059 toc21
2.0
1.6
1.2
0.8
0.4
0
I
APD
2mA/div
0mA
I
= 500µA
= 50µA
I
= 2mA
APD
APD
I
= 5µA
APD
I
MOUT
2mA/div
0mA
V
APD
-0.4
-0.8
-1.2
-1.6
-2.0
(AC-COUPLED)
2V/div
I
= 0.5µA
APD
I
APD
10
20
30
40
50
60
70
80
20µs/div
BIAS VOLTAGE (V)
STARTUP DELAY
STARTUP DELAY
MAX15059 toc22
MAX15059 toc23
SHDN
5V/div
SHDN
5V/div
V
BIAS
50V/div
V
BIAS
50V/div
I
MOUT
1mA/div
I
MOUT
500nA/div
V
= 70V
BIAS
V
= 70V,
BIAS
= 500nA
I
= 2mA
APD
I
APD
2ms/div
1ms/div
STARTUP DELAY
STARTUP DELAY
MAX15059 toc25
MAX15059 toc24
SHDN
5V/div
SHDN
5V/div
V
BIAS
5V/div
V
BIAS
5V/div
I
MOUT
1mA/div
I
MOUT
500nA/div
V
= 10V,
BIAS
= 500nA
I
APD
400µs/div
200µs/div
_______________________________________________________________________________________
7
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Typical Operating Characteristics (continued)
(V = 3.3V, V
IN OUT
= 70V, T = +25°C, unless otherwise noted.)
A
SWITCHING FREQUENCY
vs. TEMPERATURE
VOLTAGE DROP vs. APD CURRENT
SHORT-CIRCUIT RESPONSE
MAX15059 toc26
3.0
2.5
2.0
1.5
1.0
0.5
0
410
409
408
407
406
405
404
403
402
401
400
R
= 3.16kI
LIM
T = -40°C
A
V
APD
50V/div
I
MOUT
2mA/div
T = +25°C
A
T = +85°C
A
I
ILIM
5V/div
0.1
1
10
I
100
(µA)
1000 10,000
-40
-15
10
35
60
85
2µs/div
TEMPERATURE (°C)
APD
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
SWITCHING FREQUENCY AND
DUTY CYCLE vs. LOAD CURRENT
MAX15059 toc30
410
410
408
406
404
402
400
398
396
394
392
390
50
45
40
35
30
25
20
15
10
5
408
406
404
402
400
398
396
394
392
390
DUTY CYCLE
SWITCHING FREQUENCY
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
APD OUTPUT RIPPLE VOLTAGE
FB SET POINT vs. TEMPERATURE
(0.1µF FROM APD TO GROUND, V
= 70V, L
= 1mA)
BIAS
APD
MAX15059 toc32
1.240
1.238
1.236
1.234
1.232
1.230
1.228
1.226
1.224
1.222
1.220
V
APD
AC-COUPLED, 70V
1mV/div
V
= 3.3V
IN
-40
-15
10
35
60
85
1µs/div
TEMPERATURE (°C)
8
______________________________________________________________________________________
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Pin Configuration
TOP VIEW
12
11
10
9
SGND
8
7
6
5
BIAS 13
LX 14
ILIM
CNTRL
FB
MAX15059
LX
15
16
PGND
EP
4
+
1
2
3
TQFN
Pin Description
PIN
1, 16
2
NAME
PGND
IN
FUNCTION
Power Ground. Connect the negative terminals of the input and output capacitors to PGND. Connect
PGND externally to SGND at a single point, typically at the return terminal of the output capacitor.
Input-Supply Voltage. Bypass IN to PGND with a ceramic capacitor of 1FF minimum value.
Active-Low Shutdown Control Input. Apply a logic-low voltage to SHDN to shut down the device.
3
4, 8
5
SHDN
SGND
FB
Connect SHDN to IN for normal operation. Ensure that V
SHDN is internally pulled low. The converter is disabled when SHDN is left unconnected.
is not greater than the input voltage, V
.
IN
SHDN
Signal Ground. Connect directly to the local ground plane. Connect SGND to PGND at a single point,
typically near the return terminal of the output capacitor.
Feedback Regulation Input. Connect FB to the center tap of a resistive voltage-divider from the boost
output to SGND to set the output voltage. The FB voltage regulates to 1.23V (typ) when V
is
CNTRL
above 1.3V (typ) and to V
when V is below 1.2V (typ).
CNTRL
CNTRL
Control Input for Boost Converter Output-Voltage Programmability. CNTRL allows the feedback set-point
voltage to be set externally by CNTRL when CNTRL is less than 1.2V. Pull CNTRL above 1.3V (typ) to
use the internal 1.23V (typ) feedback set-point voltage.
6
CNTRL
7
9
Open-Drain Current-Limit Indicator. ILIM asserts low when the APD current limit has been exceeded.
ILIM
Current-Limit Resistor Connection. Connect a resistor from RLIM to SGND to program the APD current-
limit threshold. When RLIM is connected to SGND, the current limit is set to 4.6mA.
RLIM
Current-Monitor Output. For the MAX15059A, MOUT sources a current equal to I
. For the
APD
10
11
MOUT
MAX15059B, MOUT sources a current equal to 1/5 of I
.
APD
CLAMP
Clamp Voltage Input. CLAMP is the external potential used for voltage clamping of MOUT.
_______________________________________________________________________________________
9
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Pin Description (continued)
PIN
NAME
FUNCTION
Reference Current Output. APD provides the source current to the cathode of the photodiode.
Bias-Voltage Input. Connect BIAS to the boost converter output (V ) either directly or through a
12
APD
OUT
13
BIAS
lowpass filter for ripple attenuation. BIAS provides the voltage bias for the current monitor and is the
current source for APD.
Drain of Internal 80V n-Channel DMOS. Connect inductor to LX. Minimize the trace area at LX to reduce
switching-noise emission.
14, 15
—
LX
EP
Exposed Paddle. Connect to a large copper plane at the SGND and PGND potential to improve thermal
dissipation. Do not use as the only ground connection.
Functional Diagram
FB
OUTPUT ERROR
AND CURRENT COMPARATOR
-A
V
V
REF
LX
CNTRL
SGND
MUX
+A
80V
-C
SWITCH
CONTROL
LOGIC
DMOS
SOFT-
START
+C
PGND
PEAK
CURRENT-LIMIT
COMPARATOR
REF
REFERENCE
COMPARATOR
SWITCH
CURRENT
SENSE
V
REF
CLAMP
MOUT
BIAS
AND REF
THERMAL
SHUTDOWN
1X
CURRENT-
LIMIT
ADJUSTMENT
RLIM
IN
UVLO
CONTROL
MONITOR
CLK
APD
ILIM
1X (A)
5X (B)
CURRENT
LIMIT
OSCILLATOR
400kHz
MAX15059
BIAS
SHDN
10 _____________________________________________________________________________________
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
tion approaches ideal cycle-by-cycle control over the
output voltage since there is no conventional error ampli-
fier in the feedback path.
Detailed Description
The MAX15059 constant-frequency, current-mode, PWM
boost converters are intended for low-voltage systems
that require a locally generated high voltage. These
devices are capable of generating a low-noise, high out-
put voltage required for PIN and varactor diode biasing.
The MAX15059 operates from +2.8V to +5.5V.
The devices operate in PWM mode using a fixed-
frequency, current-mode operation. The current-mode
frequency loop regulates the peak inductor current as a
function of the output-voltage error signal.
The current-mode PWM controller is intended for DCM
operation. No internal slope compensation is added to
the current signal.
The MAX15059 operates in discontinuous mode in
order to reduce the switching noise caused by reverse
recovery charge of the rectifier diode and eliminates
the need for external compensation components. Other
continuous-mode boost converters generate large volt-
age spikes at the output when the LX switch turns on
because there is a conduction path between the output,
diode, and switch to ground during the time needed
for the diode to turn off and reverse its bias voltage. To
reduce the output noise even further, the LX switch turns
off by taking 10ns typically to transition from on to off.
As a consequence, the positive slew rate of the LX node
is reduced and the current from the inductor does not
“force” the output voltage as hard as would be the case
if the LX switch were to turn off faster.
Current Limit
The current limit of the current monitor is programmable
from 1mA to 4.6mA (typ). Connect RLIM to SGND to get
a default current-limit threshold of 4.6mA or connect a
resistor from RLIM to SGND to program the current-limit
threshold below the default setting of 4.6mA. Calculate
the value of the external resistor, R , for a given cur-
LIM
rent limit, I , using the following equation:
LIM
1.23V
R
(kΩ) =
x10 − 2.67(kΩ)
LIM
I
(mA)
LIM
The constant-frequency (400kHz) PWM architecture
generates an output voltage ripple that is easy to filter.
An 80V lateral DMOS device used as the internal power
switch is ideal for boost converters with output voltages
up to 76V. The MAX15059 can also be used in other
topologies where the PWM switch is grounded, like
SEPIC and flyback converters.
Clamping the Monitor Output Voltage
(MOUT)
CLAMP provides a means for diode clamping the volt-
age at MOUT; thus, V
is limited to (V
+ 0.6V).
MOUT
CLAMP
CLAMP can be connected to either an external supply or
BIAS. Leave CLAMP unconnected if voltage clamping is
not required.
The MAX15059 includes a versatile current monitor
intended for monitoring the APD, PIN, or varactor
diode DC current in fiber and other applications. The
MAX15059 features more than three decades of dynam-
ic current ranging from 500nA to 4mA and provides an
output current accurately proportional to the APD current
at MOUT. MOUT output accuracy is Q10% from 500nA to
1mA and Q5% from 1mA to 2mA.
Shutdown
The MAX15059 features an active-low shutdown input
(SHDN). Pull SHDN low or leave it unconnected to enter
shutdown. During shutdown, the supply current drops
to 2FA (max). The output remains connected to the
input through the inductor and output rectifier, holding
the output voltage to one diode drop below IN when
the MAX15059 is in shutdown. Connect SHDN to IN for
always-on operation.
The MAX15059 also features a shutdown logic input to
disable the device and reduce its standby current to 2FA
(max).
Adjusting the Feedback
Set-Point/Reference Voltage
Apply a voltage to the CNTRL input to set the feedback
Fixed-Frequency PWM Controller
The heart of the MAX15059 current-mode PWM control-
ler is a BiCMOS multi-input comparator that simulta-
neously processes the output-error signal and switch
current signal. The main PWM comparator uses direct
summing, lacking a traditional error amplifier and its
associated phase shift. The direct summing configura-
set-point reference voltage, V
(see the Functional
REF
Diagram). For V
> 1.3V, the internal 1.23V (typ)
CNTRL
reference voltage is used as the feedback set point and
for V < 1.2V, the CNTRL voltage is used as the
CNTRL
reference voltage (V set equal to V
).
FB
CNTRL
______________________________________________________________________________________ 11
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Determining the Inductor Value
Three key inductor parameters must be specified for
operation with the MAX15059: inductance value (L),
Design Procedure
Setting the Output Voltage
Set the MAX15059 output voltage by connecting a resis-
tive divider from the output to FB to SGND (Figure 1).
inductor saturation current (I
), and DC resistance
SAT
(DCR). In general, the inductor should have a saturation
current rating greater than the maximum peak switch
Select R (FB to SGND resistor) between 5kIand 10kI.
1
Calculate R (V
equation:
to FB resistor) using the following
2
OUT
current-limit value (I
= 1.3A). DC series resistance
LIM_LX
(DCR) should be be low for reasonable efficiency.
Use the following formula to calculate the lower bound of
the inductor value at different output voltages and output
currents. This is the minimum inductance value for dis-
continuous mode operation for supplying full 300mW of
output power:
V
OUT
R
2
= R
−1
1
V
REF
where V
can range from (V + 5V) to 76V. Apply a
IN
voltage to the CNTRL input to set the feedback set-point
reference voltage, V (see the Functional Diagram).
> 1.3V, the internal 1.23 (typ) reference volt-
age is used as the feedback set point and for V
OUT
2 × t ×I
× (V
− V
)
REF
S
OUT
OUT
IN_MIN
L
[µH] =
MIN
For V
2
CNTRL
η×I
LIM_LX
<
CNTRL
1.2V, V
= V
. See the Adjusting the Feedback
REF
CNTRL
where V
, V
(both in volts), and I
(in amps)
IN_MIN OUT
OUT
Set-Point/Reference Voltage section for more information
on adjusting the feedback reference voltage, V
are typical values (so that efficiency is optimum for typi-
cal conditions), t (in Fs) is the period, Eis the efficiency,
.
REF
S
and I
is the peak switch current in amps (see the
Determining Peak Inductor Current
If the boost converter remains in the discontinuous mode
of operation, then the approximate peak inductor cur-
LIM_LX
Electrical Characteristics table).
Calculate the optimum value of L (L
) to ensure
OPTIMUM
rent, I
(in A), is represented by the formula below:
LPEAK
the full output power without reaching the boundary
between continuous-conduction mode (CCM) and dis-
continuous-conduction mode (DCM) using the following
formula:
2 × t × (V
− V
)×I
S
OUT
IN_MIN OUT_MAX
I
=
LPEAK
η×L
where t is the switching period in Fs, V
is the output
OUT
L
[µH]
S
MAX
L
[µH] =
OPTIMUM
voltage in volts, V
is the minimum input voltage
IN_MIN
2.25
in volts, I
is the maximum output current in
OUT_MAX
amps, L is the inductor value in FH, and E is the effi-
ciency of the boost converter (see the Typical Operating
Characteristics).
where:
L
2
V
(V
− V
)× t × η
S
OUT
IN_MIN
2
IN_MIN
[µH] =
MAX
2 ×I
× V
OUT
OUT
For a design in which V = 3.3V, V
= 70V, I
=
=
IN
OUT
S
OUT
MAX
V
3mA, E = 45%, I
= 1.2A, and t = 2.5Fs: L
OUT
LIM_LX
27FH and L
= 1.5FH.
MIN
R
R
2
1
MAX15059
For a worse-case scenario in which V = 2.8V, V
IN
OUT
= 70V, I
2.5Fs: L
= 4mA, η = 43%, I
= 15FH and L
= 1.2A, and t =
OUT
MAX
LIM_LX S
FB
V
V
> 1.3V, V = 1.23V
FB
CNTRL
CNTRL
= 2.2FH.
MIN
< 1.2V, V = V
FB CNTRL
The choice of 4.7FH is reasonable given the worst-case
scenario above. In general, the higher the inductance,
the lower the switching noise. Load regulation is also
better with higher inductance.
Figure 1. Adjustable Output Voltage
12 _____________________________________________________________________________________
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Diode Selection
The MAX15059’s high switching frequency demands a
high-speed rectifier. Schottky diodes are recommended
for most applications because of their fast recovery time
and low forward-voltage drop. Ensure that the diode’s
peak current rating is greater than the peak inductor cur-
rent. Also, the diode breakdown voltage must be greater
V
= 2.8V
IN
L1
TO 5.5V
C
IN
IN
D1
R
F
V
OUT
CNTRL
SHDN
LX
than V
.
OUT
Output Filter Capacitor Selection
R
R
2
MAX15059
C
IN
For most applications, use a small output capacitor of
0.1FF or greater. To achieve low output ripple, a capaci-
tor with low ESR, low ESL, and high capacitance value
should be selected. If tantalum or electrolytic capacitors
are used to achieve high capacitance values, always
add a smaller ceramic capacitor in parallel to bypass the
high-frequency components of the diode current. The
higher ESR and ESL of electrolytic capacitors increase
the output ripple and peak-to-peak transient voltage.
Assuming the contribution from the ESR and capacitor
discharge equals 50% (proportions may vary), calculate
the output capacitance and ESR required for a specified
ripple using the following equations:
FB
C
OUT
C
F
1
PGND
BIAS
SGND
Figure 2. Typical Operating Circuit with RC Filter
Input-Capacitor Selection
Bypass IN to PGND with a 1FF (min) ceramic capacitor.
Depending on the supply source impedance, higher val-
ues may be needed. Make sure that the input capacitors
are close enough to the IC to provide adequate decou-
pling at IN as well. If the layout cannot achieve this,
add another 0.1FF ceramic capacitor between IN and
PGND in the immediate vicinity of the IC. Bulk aluminum
electrolytic capacitors may be needed to avoid chatter-
ing at low-input voltage. In case of aluminum electrolytic
capacitors, calculate the capacitor value and ESR of the
input capacitor using the following equations:
I
I
x L
OPTIMUM
OUT
LPEAK
(V
C
[µF] =
t −
S
OUT
0.5 x ∆V
− V
)
OUT
OUT
IN_MIN
0.5x∆V
OUT
OUT
ESR mΩ =
[
]
I
For very-low-output-ripple applications, the output of the
boost converter can be followed by an RC filter to further
reduce the ripple. Figure 2 shows a 100I, 0.1FF (R C )
filter used to reduce the switching output ripple to 1mV
with a 0.1mA load or 1mV
F
F
P-
with a 4mA load. The
P
P-P
output voltage regulation resistive divider must remain
connected to the diode/output capacitor node.
V
x I
I
x L
x V
Use X7R ceramic capacitors for more stability over the
full temperature range.
OUT
OUT
x 0.5 x ∆V
LPEAK
V
OPTIMUM
(V − V
OUT
)
C
[µF] =
IN
t −
S
η x V
IN_MIN
IN
IN_MIN OUT
IN_MIN
0.5x∆V x η x V
IN IN_MIN
ESR mΩ =
[
]
V
x I
OUT OUT
______________________________________________________________________________________ 13
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
In some applications where pilot tones are used to identi-
Applications Information
Using APD or PIN Photodiodes
in Fiber Applications
fy specific fiber channels, higher bandwidths are desired
at MOUT to detect these tones. Consider the minimum
and maximum currents to be detected, then consult the
frequency response and noise typical operating curves.
If the minimum current is too small, insufficient band-
width could result, while too high a current could result in
excessive noise across the desired bandwidth.
When using the MAX15059 to monitor APD or PIN photo-
diode currents in fiber applications, several issues must
be addressed. In applications where the photodiode
must be fully depleted, keep track of voltages budgeted
for each component with respect to the available supply
voltage(s). The current monitors require as much as 3.5V
between BIAS and APD, which must be considered part
of the overall voltage budget.
Layout Considerations
Careful PCB layout is critical to achieve low switching
losses and clean and stable operation. Protect sensitive
analog grounds by using a star ground configuration.
Connect SGND and PGND together close to the device
at the return terminal of the output bypass capacitor. Do
not connect them together anywhere else. Keep all PCB
traces as short as possible to reduce stray capacitance,
trace resistance, and radiated noise. Ensure that the
feedback connection to FB is short and direct. Route
high-speed switching nodes away from the sensitive
analog areas. Use an internal PCB layer for SGND as an
EMI shield to keep radiated noise away from the device,
feedback dividers, and analog bypass capacitors. Refer
to the MAX15059 Evaluation Kit data sheet for a layout
example.
Additional voltage margin can be created if a nega-
tive supply is used in place of a ground connection,
as long as the overall voltage drop experienced by
the MAX15059 is less than or equal to 76V. For this
type of application, the MAX15059 is suggested so the
output can be referenced to “true” ground and not the
negative supply. The MAX15059’s output current can
be referenced as desired with either a resistor to ground
or a transimpedance amplifier. Take care to ensure
that output voltage excursions do not interfere with the
required margin between BIAS and MOUT. In many fiber
applications, MOUT is connected directly to an ADC
that operates from a supply voltage that is less than the
voltage at BIAS. Connecting the MAX15059’s clamping
diode output, CLAMP, to the ADC power supply helps
avoid damage to the ADC. Without this protection, volt-
ages can develop at MOUT that might destroy the ADC.
This protection is less critical when MOUT is connected
directly to subsequent transimpedance amplifiers (linear
or logarithmic) that have low-impedance, near-ground-
referenced inputs. If a transimpedance amp is used on
the low side of the photodiode, its voltage drop must
also be considered. Leakage from the clamping diode
is most often insignificant over nominal operating condi-
tions, but grows with temperature.
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land pat-
terns, go to www.maxim-ic.com/packages. Note that
a “+”, “#”, or “-” in the package code indicates RoHS
status only. Package drawings may show a different suf-
fix character, but the drawing pertains to the package
regardless of RoHS status.
To maintain low levels of wideband noise, lowpass filter-
ing the output signal is suggested in applications where
only DC measurements are required. Connect the filter
capacitor at MOUT. Determining the required filtering
components is straightforward, as the MAX15059 exhib-
its a very high output impedance of 5GI.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
16 TQFN-EP
T1633-4
21-0136
14 _____________________________________________________________________________________
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
1
1/10
3/10
Initial release
Replaced five TOCs, added three TOCs, updated text
—
1, 2, 3, 5–8, 11
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
©
2010 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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