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參數(shù)資料
| 型號： | MAX8520 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Smallest TEC Power Drivers for Optical Modules |
| 中文描述： | 尺寸最小的TEC電源驅(qū)動器，用于光模塊 |
| 文件頁數(shù)： | 10/19頁 |
| 文件大?。?/td> | 605K |
| 代理商： | MAX8520 |
M
Smallest TEC Power Drivers for
Optical Modules
10
______________________________________________________________________________________
Detailed Description
The MAX8520/MAX8521 TEC drivers consist of two
switching buck regulators that operate together to directly
control the TEC current. This configuration creates a
differential voltage across the TEC, allowing bidirectional
TEC current for controlled cooling and heating. Controlled
cooling and heating allow accurate TEC temperature con-
trol to within ±0.01
°
C. The voltage at CTLI directly sets
the TEC current. An external thermal- control loop is typi-
cally used to drive CTLI. Figures 1 and 2 show examples
of the thermal control-loop circuit.
Ripple Cancellation
Switching regulators like those used in the MAX8520/
MAX8521 inherently create ripple voltage on the output.
The dual regulators in the MAX8520/MAX8521 switch in
phase and provide complementary in-phase duty
cycles so ripple waveforms at the TEC are greatly
reduced. This feature suppresses ripple currents and
electrical noise at the TEC to prevent interference with
the laser diode.
Switching Frequency
For the MAX8521, FREQ sets the switching frequency of
the internal oscillator. With FREQ = GND, the oscillator
frequency is set to 500kHz. The oscillator frequency is
1MHz when FREQ = V
DD
.
For the MAX8520, connect a resistor (R
EXT
in Figure 2)
from FREQ to GND. Choose R
EXT
= 60k
for 1MHz
operation, and R
EXT
= 150k
for 500kHz operation. For
any intermediary frequency between 500kHz and
1MHz, use the following equation to find the value of
R
EXT
value needed for V
DD
= 5V:
where R
EXT
is the resistance given in k
, and fs is the
desired frequency given in MHz. Note that for V
DD
<
5V, the frequency is reduced slightly, to the extent of
about 7% when V
DD
reaches 3V. This should be taken
into consideration when selecting the value for R
EXT
at
a known supply voltage.
Voltage and Current-Limit Setting
Both the MAX8520 and MAX8521 provide control of the
maximum differential TEC voltage. Applying a voltage
to MAXV limits the maximum voltage across the TEC.
The voltage at MAXIP and MAXIN sets the maximum
positive and negative current through the TEC. These
current limits can be independently controlled.
Current Monitor Output
ITEC provides a voltage output proportional to the TEC
current (I
TEC
). See the
Functional Diagram
for more
details:
V
ITEC
= 1.5V +(8
(VOS1-VCS))
Reference Output
The MAX8520/MAX8521 include an on-chip voltage ref-
erence. The 1.50V reference is accurate to 1% over
temperature. Bypass REF with 0.1μF to GND. REF can
be used to bias an external thermistor for temperature
sensing as shown in Figures 1 and 2.
Thermal and Fault-Current Protection
The MAX8520/MAX8521 provide fault-current protection
in either FET by turning off both high-side and low-side
FETs when the peak current exceeds 3A in either FET. In
addition, thermal-overload protection limits the total
power dissipation in the chip. When the device
’
s die junc-
tion temperature exceeds +165
°
C, an on-chip thermal
sensor shuts down the device. The thermal sensor turns
the device on again after the junction temperature cools
down by 15
°
C.
Design Procedures
Duty-Cycle Range Selection
By design, the MAX8520/MAX8521 are capable of oper-
ating from 0% to 100% duty cycle, allowing both LX out-
puts to enter dropout. However, as the LX pulse width
narrows, accurate duty-cycle control becomes difficult.
This can result in a low-frequency noise appearing at the
TEC output (typically in the 20kHz to 50kHz range). While
this noise is typically filtered out by the low thermal-loop
bandwidth, for best results, operate the PWM with a pulse
width greater than 200ns. For a 500kHz application, the
recommended duty-cycle range is from 10% to 90%. For
a 1MHz application, it is from 20% to 80%.
R
fs
EXT
=
×
90
1
1
3
TEC CONNECTION
Heating mode
Cooling mode
THERMISTOR
PTC
NTC
Table 1. TEC Connection for Figure 1
TEC CONNECTION
Heating mode
Cooling mode
THERMISTOR
NTC
PTC
Table 2. TEC Connection for Figure 2
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8520ETP | 功能描述:其他電源管理 RoHS:否 制造商:Texas Instruments 輸出電壓范圍: 輸出電流:4 mA 輸入電壓范圍:3 V to 3.6 V 輸入電流: 功率耗散: 工作溫度范圍:- 40 C to + 110 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-48 封裝:Reel |
| MAX8520ETP/GG8 | 制造商:Maxim Integrated Products 功能描述: |
| MAX8520ETP+ | 功能描述:顯示驅(qū)動器和控制器 TEC Power Driver for Optical Modules RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| MAX8520ETP+T | 功能描述:其他電源管理 TEC Power Driver for Optical Modules RoHS:否 制造商:Texas Instruments 輸出電壓范圍: 輸出電流:4 mA 輸入電壓范圍:3 V to 3.6 V 輸入電流: 功率耗散: 工作溫度范圍:- 40 C to + 110 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-48 封裝:Reel |
| MAX8520ETP-T | 功能描述:其他電源管理 RoHS:否 制造商:Texas Instruments 輸出電壓范圍: 輸出電流:4 mA 輸入電壓范圍:3 V to 3.6 V 輸入電流: 功率耗散: 工作溫度范圍:- 40 C to + 110 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-48 封裝:Reel |
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