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參數(shù)資料
| 型號： | ADN8810ACP-REEL7 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 模擬信號調(diào)理 |
| 英文描述： | 12-Bit High Output Current Source |
| 中文描述： | SPECIALTY ANALOG CIRCUIT, QCC24 |
| 封裝： | 4 X 4 MM, MO-220VGGD-2, LFCSP-24 |
| 文件頁數(shù)： | 13/16頁 |
| 文件大?。?/td> | 232K |
| 代理商： | ADN8810ACP-REEL7 |
ADN8810
Rev. 0 | Page 13 of 16
DITHER
4.096V
R1
1.62k
R2
1.62k
C
1
μ
F
5V
AD8605
TO V
REF
0
Figure 19. Adding Dither to the Reference Voltage
Set the gain of the dither by adjusting the ratio of R2 to R1.
Increase C to lower the cutoff frequency of the high-pass filter
created by C and R1. The cutoff frequency of Figure 19 is
approximately 10 Hz.
The AD8605 is recommended as a low offset, rail-to-rail input
amplifier for this circuit.
DRIVING COMMON-ANODE LASER DIODES
The ADN8810 can power common-anode laser diodes. These
are laser diodes whose anodes are fixed to the laser module
case. The module case is typically tied to either VDD or ground.
For common-anode-to-ground applications, a negative 5 V
supply must be provided.
In Figure 20, R
S
sets up the diode current by the equation
4096
5
16
1
1
1
×
096
.
Code
k
R
I
S
×
+
=
(5)
where
Code
is an integer value from 0 to 4,095. Using the values
in Figure 20, the diode current is 300.7 mA at a code value of
2,045 (0
x
7FF), or one-half full-scale. This effectively provides
11-bit current control from 0 mA to 300 mA of diode current.
The maximum output current of this configuration is limited by
the compliance voltage at the IOUT pin of the ADN8810. The
voltage at IOUT cannot exceed 1 V below PVDD, in this case
4 V. The IOUT voltage is equal to the voltage drop across R
S
plus
the gate-to-source voltage of the external FET. For this reason,
select a FET with a low threshold voltage.
In addition, the voltage across the R
S
resistor cannot exceed the
voltage at the cathode of the laser diode. Given a forward laser
diode voltage drop of 2 V in Figure 20, the voltage at the R
SN
pin
(I
×
R
S
) cannot exceed 3 V. This sets an upper limit to the value
of
Code
in Equation 5.
Although the configuration for anode-to-ground diodes is
similar, the supply voltages must be shifted down to 0 V and
–5 V, as shown in Figure. The AVDD, DVDD, and PVDD pins
are connected to ground with AVSS connected to –5 V. The
4.096 V reference must also be referred to the –5 V supply
voltage. The diode current is still determined by Equation 5.
All logic levels must be shifted down to 0 V and –5 V levels as
well. This includes RESET, CS, SCLK, SDI, SB, and all ADDR
pins. Figure shows a simple method to level shift a standard
TTL or CMOS (0 V to 5 V) signal down using external FETs.
FB
NC
D1
I = 300mA
@ CODE 0x7F
FDC633N
OR EQUIV
IOUT
R
SN
3
VOUT
VIN
GND
ADR292
R
6.81
NOTE: LEAVE FB WITH NO CONNECTION
ADN8810
5V
DGND
DVSS
AVSS
5V
5V
SB
PVDD
AVDD
DVDD
ENCOMP
ADDR0-2
SDI
SCLK
TTL/CMOS
LOGIC LEVELS
CS
RESET
VREF
0
Figure 20. Driving Common-Anode-to-VDD Laser Diodes
FB
NC
D1
I = 300mA
@ CODE 0x7F
FDC633N
OR EQUIV
IOUT
R
SN
3
VOUT
VIN
GND
ADR292
R
6.81
NOTE: LEAVE FB WITH NO CONNECTION
ADN8810
–5V
–5V
–5V
–5V
DGND
DVSS
AVSS
SB
PVDD
AVDD
DVDD
ENCOMP
ADDR0-2
SDI
SCLK
–5 TO 0V
LOGIC LEVELS
CS
RESET
VREF
0
Figure 21. Driving Common-Anode-to-Ground Laser Diodes with a Negative
Supply
NDC7003P
OR EQUIV
10k
100k
TO:
+3V
–5V
–5V
TTL/CMOS
LEVEL
RESET
CS
SCLK
SDI
NDC7002N
OR EQUIV
0
Figure 22. Level Shifting TTL/CMOS Logic
PC BOARD LAYOUT RECOMMENDATIONS
Although they can be driven from the same power supply
voltage, keep DVDD and AVDD current paths separate on the
PC board to maintain the highest accuracy; likewise for AVSS
and DGND. Tie common potentials together at a single point
located near the power regulator. This technique is known as
star grounding and is shown in Figure. This method reduces
digital crosstalk into the laser diode or load.
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| ADN8810ACPZ | 功能描述:IC CURRENT SOURCE 12BIT 24LFCSP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)流/電流管理 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:50 系列:- 功能:電流開關(guān) 檢測方法:- 精確度:±10% 輸入電壓:1.7 V ~ 5.5 V 電流 - 輸出:600mA 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-UFQFN 供應(yīng)商設(shè)備封裝:10-UTQFN（1.4x1.8） 包裝:管件 |
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