參數(shù)資料
型號(hào)： MAX1932
廠商： Maxim Integrated Products, Inc.
英文描述： Digitally Controlled, 0.5% Accurate, Safest APD Bias Supply
中文描述： 數(shù)控、0.5%精度、更安全的APD偏置電源
文件頁(yè)數(shù)： 7/16頁(yè)
文件大?。?/td> 399K
代理商： MAX1932
Output and DAC Adjustments Range
Many biasing applications require an adjustable output
voltage, which is easily obtained using the MAX1932
’
s
DAC output (Figure 2).
The DAC output voltage is given by the following equation:
On power-up, DACOUT defaults to FF hex or 1.25V,
which corresponds to the minimum V
OUT
output voltage.
The voltage generated at DACOUT is coupled to FB
through R6. DACOUT can sink only 50μA so:
Select the minimum output voltage (V
OUTFF
), and the
maximum output voltage (V
OUT01
) for the desired
adjustment range. R5 sets the adjustment span using
the following equation:
R5 = (V
OUTFF
- V
OUT01
) (R6/1.25V)
R8 sets the minimum output of the adjustment range
with the following equation:
R8 = (1.25V
R5)/(V
OUTFF
)
Setting the Output Voltage without
the DAC
Adjust the output voltage by connecting a voltage-
divider from the output (V
OUT
) to FB (Figure 2 with R6
omitted). Select R8 between 10k
to 50k
. Calculate
R5 with the following equation:
Inductor Selection
Optimum inductor selection depends on input voltage,
output voltage, maximum output current, switching fre-
quency, and inductor size. Inductors are typically spec-
ified by their inductance (L), peak current (I
PK
), and
resistance (L
R
).
The inductance value is given by:
where V
IN
is the input voltage, I
OUT(MAX)
is the maxi-
mum output current delivered, V
OUT
is the output volt-
age, and T is the switching period (3.3μs),
η
is the
estimated power conversion efficiency, and D is the
maximum duty cycle:
D < (V
OUT
- V
IN
)/V
OUT
up to a maximum of 0.9
Since the L equation factors in efficiency, for inductor cal-
culation purposes, an
η
of 0.5 to 0.75 is usually suitable.
For example, with a maximum DC load current of 2.5mA,
a 90V output, V
IN
= 5V, D = 0.9, T = 3.3μs, and
η
esti-
mated at 0.75, the above equation yields an L of 111μH,
so 100μH would be a suitable value.
The peak inductor current is given by:
These are typical calculations. For worst case, refer to
the article titled
“
Choosing the MAX1932 External
Indicator, Diode, Current Sense Resistor, and Output
Filter Capacitor for Worst Case Conditions
”
located on
the Maxim website in the Application Notes section (visit
www.maxim-ic.com/an1805).
External Power-Transistor Selection
An N-FET power switch is required for the MAX1932. The
N-FET switch should be selected to have adequate on-
resistance with the MOSFET V
GS
= V
IN(MIN)
. The break-
down voltage of the N-FET must be greater than V
OUT
.
For higher-current output applications (such as 5mA at
90V), SOT23 high-voltage low-gate-threshold N-FETs
may not have adequate current capability. For example,
with a 5V input, a 90V, 5mA output requires an inductor
peak of 240mA. For such cases it may be necessary to
simply parallel two N-FETs to achieve the required cur-
rent rating. With SOT23 devices this often results in
smaller and lower cost than using a larger N-FET device.
Diode Selection
The output diode should be rated to handle the output
voltage and the peak switch current. Make sure that the
diode
’
s peak current rating is at least I
PK
and that its
breakdown voltage exceeds V
OUT
. Fast reverse recov-
ery time (t
rr
< 10ns) and low junction capacitance
I
V
D T
L
PK
IN
=
×
L
V
I
OUT MAX
2
D
T
V
IN
OUT
=
(
)
×
(
×
×
×
2
2
η
)
R
R
VOUT
1 25
.
V
5
8
1
=
R
V
A
6
1 25
50
≥
μ
.
V
CODE
V
V
DACOUT
=
×
+
1 25
256
1 25
256
.
.
M
Digitally Controlled, 0.5% Accurate, Safest APD
Bias Supply
_______________________________________________________________________________________
7
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MAX1932ETC 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel
MAX1932ETC/GG8 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel
MAX1932ETC+ 功能描述:其他電源管理 0.5% Accurate APD Bias Supply 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(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-48 封裝:Reel
MAX1932ETC+ 制造商:Maxim Integrated Products 功能描述:SUPPLY BIAS APD SMD 1932 TQFN12 制造商:Maxim Integrated Products 功能描述:SUPPLY BIAS, APD, SMD, 1932, TQFN12
MAX1932ETC+T 功能描述:其他電源管理 0.5% Accurate APD Bias Supply 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(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-48 封裝:Reel
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