|
|
Part: AN1995
Category:
Description:
Company:
Datasheet: Download AN1995 datasheet File size : 83 kB
Request For quote: Find where to buy AN1995
Datasheet text preview:
RF COMMUNICATIONS PRODUCTS
AN1995 Evaluating the SA605 SO and SSOP demo-board
Alvin K. Wong 1997 Oct 29
Philips Semiconductors
Philips Semiconductors
Application note
Evaluating the SA605 SO and SSOP demo-board
Author: Alvin K. Wong
AN1995
INTRODUCTION
With the increasing demand for smaller and lighter equipment, designers are forced to reduce the physical size of their systems. There are several approaches to solving the size problem. A designer needs to look for sophisticated integrated single chip solutions, chips that are smaller in size, and chips that require minimum external components. Philips Semiconductors offers all of these solutions in their SA605. The SA605 single-chip receiver converts the RF signal to audio and is available in three packages: DIP,SO, and SSOP. This offers total flexibility for layout considerations. The SSOP package is the smallest 20 pin package available in the market today, and allows the designer the flexibility to reduce the overall size of a layout. When working with a smaller and tighter layout in a receiver design, it becomes important to follow good RF techniques. This application note shows the techniques used in the SO and SSOP demo-board. It does not cover the basic functionality of the SA605 but instead focuses more on the layout constraints. This application note also has a trouble-shooting chart to aid the designer in evaluating the SO and SSOP demo-board. For a complete explanation of the SA605, please refer to application note AN1994 which describes the basic block diagrams, reviews the common problems encountered with the SA605, and suggests solutions to them. Reading AN1994 is highly recommended before attempting the SO and SSOP layout.
The recommended layout demonstrates how well the chip can perform. But it should be pointed out that the combination of external parts with their tolerances plays a role in achieving maximum sensitivity. The minimum and maximum 12dB SINAD measurement for both boards is -118dBm and -119.7dBm, respectively. A typical reading taken in the lab for both SO and SSOP demo-boards is -119dBm. There were two different design approaches for both layouts. For the SO layout, there are inductive tuning elements (except for the LO section); for the SSOP layout there are capacitive tuning elements. This approach was taken to show the designer that both ways can be used to achieve the same 12dB SINAD measurement. However, it is worth mentioning that capacitive tuning elements are less expensive than the inductive tuning elements.
Packages Available
As mentioned above, there are three packages available for the SA605. See the "Package Outline" section of the Philips Semiconductors 1992 RF Handbook for the physical dimensions of all three packages. Notice that the DIP package is the largest of the three in physical size; the SSOP is the smallest. The recommended layout and performance graphs for the DIP package are shown in the SA605 data sheet and AN1994. But the SO and SSOP recommended layout and performance graphs are shown in this application note.
SMA RF IN
45MHz C1 56pF L1 330nH
VCC + C10 22 µ F L2 1.2 µ H C7 1nF
C2 150pF U1 C5 .1 µ F 1 2 3 4 5 6 7 8 9 10 RFIN BYPASS OSC OUT OSC IN MUTE IN VCC RSSI OUT AUDIO OUT DATA OUT QUAD IN SA605D MXR OUT DECOUP IF IN DECOUP IF OUT GND LIM IN DECOUP DECOUP LIM OUT 20 19 18 17 16 15 14 13 12 11
FILT1 1 I C21 .1 µ F C23 .1 µ F FILT2 1 R17 5.1k I G 2 D 3 G 2 D 3
C6 30pF TRMR C8 10pF X1 44.545MHz C9 .1 µ F R9 100k
C15 10pF C11 .1 µ F
C17 .1 µ F C18 .1 µ F
RSSI R10 100k C26 390pF
IFT1 330 µ H Var.
C12 .015 µ F AUDIO R11 100k
C14 .1 µ F
C13 150pF DATA
SR00876
Figure 1. SA605 Schematic for the SO Layout
1997 Oct 29
62
Philips Semiconductors
Application note
Evaluating the SA605 SO and SSOP demo-board
AN1995
SA605D SA605D
1.7 in.
TOP SILK SCREEN
TOP VIEW
1.75 in. BOTTOM VIEW
SR00877
Figure 2. SA605 SO Demo-board Layout (Not Actual Size)
10 AUDIO 0 10 20 dB 30 40 50 AM REJECTION (dB) 60 NOISE (dB) 70 125 115 105 95 85 75 65 55 45 35 25 THD + N(dB)
RF LEVEL (dBm) 4.75 4.50 4.25 4.00 3.75 3.50 3.25 3.00 2.75 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0.00 125 RSSI (V)
VOLTS
115
105
95
85
75
65
55
45
35
25
RF LEVEL (dBm)
SR00878
Figure 3. SA605 SO Performance Curves
SO LAYOUT:
Figure 1 shows the schematic for the SO layout. Listed below are the basic functions of each external component for Figure 1. C1 C2 C5 C6 Part of the tapped-C network to match the front-end Part of the tapped-C network to match the front-end Used as an AC short to Pin 2 Used to tune the LO for the Colpitts oscillator
C7 C8 C9
Used as part of the Colpitts oscillator Used as part of the Colpitts oscillator Supply bypassing
C10 Supply bypassing C11 Used as filter C12 Used as filter
1997 Oct 29
63
Philips Semiconductors
Application note
Evaluating the SA605 SO and SSOP demo-board
AN1995
C13 Used as filter C14 Used to AC ground the Quad tank C15 Used to provide the 90° phase shift to the phase detector C17 IF limiter decoupling cap C18 IF limiter decoupling cap C21 IF amp decoupling cap C23 IF amp decoupling cap C26 Quad tank component L1 L2 R9 Part of tapped-C network to match the front-end TOKO 5CB-1320Z Part of the Colpitts oscillator Coilcraft 1008CS-122 Used to convert the current into the RSSI voltage
C3 TRMR
R10 Converts the audio current to a voltage R11 Converts the data current to a voltage R17 Used to achieve the 12dB insertion loss IFT1 Inductor for the Quad tank TOKO 303LN-1130 FILT1 Murata SFG455A3 455kHz bandpass filter FILT2 Murata SFG455A3 455kHz bandpass filter X1 Standard 44.545MHz crystal in QC38 package
The recommended SO layout can be found in Figure 2 and should be used as an example to help designers get started with their projects. The SO SA605 board performance graphs can be found in Figure 3.
30pF SMA RF IN VCC + C10 22 µ F L2 C7 1.2 µ H 1nF 45MHz
C1
33pF L1 330nH C2 U1 1 2 3 4 5 6 7 8 9 10 RFIN BYPASS OSC OUT OSC IN MUTE IN VCC RSSI OUT AUDIO OUT DATA OUT QUAD IN SA605DK MXR OUT DECOUP IF IN DECOUP IF OUT GND LIM IN DECOUP DECOUP LIM OUT 20 19 18 17 16 15 14 13 12 11 1 I C23 .1 µ F
FILT1 3 G 2 D
180pF C5 .1 µ F
C21 .1 µ F FILT2 1 R17 5.1k I G 2 D 3
C6 30pF TRMR C8 10pF X1 44.545MHz C9 .1 µ F R9 100k
C15 10pF C11 .1 µ F C17 C24 30pF TRMR 100k R11 C14 .1 µ F C13 150pF C25 68pF C26 470pF IFT1 220 µ H .1 µ F C18 .1 µ F
RSSI
R10 100k
C12 AUDIO DATA
.015 µ F
SR00879
Figure 4. SA605 Schematic for the SSOP Layout
SSOP LAYOUT:
Figure 4 shows the schematic for the SSOP layout. C1 C2 C3 C5 C6 C7 C8 C9 Part of the tapped-C network to match the front-end Part of the tapped-C network to match the front-end Part of the tapped-C network to match the front-end Used as an AC short to Pin 2 Used to tune the LO for the Colpitts oscillator Used as part of the Colpitts oscillator Used as part of the Colpitts oscillator Supply bypassing
C14 Used to AC ground the Quad tank C15 Used to provide the 90° phase shift to the phase detector C17 IF limiter decoupling cap C18 IF limiter decoupling cap C21 IF amp decoupling cap C23 IF amp decoupling cap C24 Part of the Quad tank C25 Part of the Quad tank C26 Part of the Quad tank L1 L2 R9 Part of tapped-C network to match the front-end Coilcraft 1008CS-331 Part of the Colpitts oscillator Coilcraft 1008CS-122 Used to convert the current into the RSSI voltage
C10 Supply bypassing C11 Used as filter C12 Used as filter C13 Used as filter
R10 Converts the audio current to a voltage
1997 Oct 29
64
Philips Semiconductors
Application note
Evaluating the SA605 SO and SSOP demo-board
AN1995
R11 Converts the data current to a voltage R17 Used to achieve the 12dB insertion loss IFT1 Inductor for the Quad tank Mouser ME435-2200 FILT1 Murata SFGCC455BX 455kHz bandpass filter FILT2 Murata SFGCC455BX 455kHz bandpass filter X1 Standard 44.545MHz crystal
The SSOP layout can be found in Figure 5. The SSOP SA605 board performance graphs can be found in Figure 6. The main difference between the SO and SSOP demo-boards is that the SSOP demo-board incorporates the low profile 455kHz Murata ceramic filter. It has an input and output impedance of 1.0k. This presents a mismatch to our chips, but we have found that the overall performance is similar to that when we use the "blue" Murata filters that have the proper 1.5k input and output impedance.
SA605DK
TOP SILK SCREEN
TOP VIEW
1.6 in.
1.7 in. BOTTOM VIEW
SR00880
Figure 5. SA605 SSOP Demo-board Layout (Not Actual Size)
1997 Oct 29
65
Others parts begin by an
AN-1 AN-2 AN-3 AN-4 AN-5 AN-6 AN-7 AN-8
|
|
|
