ST AN2122 Application note
AN2122
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®
APPLICATION NOTE
TV Hardware Design Rules:
PCB Compatibility with ST92196/186
Introduction
The purpose of this application note is to:
1. Describe how to design a printed circuit board (PCB) with optimum performance and
compatiblity between ST92E196 or ST92T196 (SDIP56 package), and ST92186 (SDIP32 and
SDIP42 packages) microcontrollers.
2. Describe the external filters and components needed for the ST92186 family of
microcontrollers (MCU).
3. Provide advice on how to develop applications for ST92186 microcontrollers in SDIP32 or
SDIP42 packages using ST92E196 / ST92T196 devices.
AN2122/0205 1/15
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AN2122
Table of Contents
Introduction 1
Chapter 1 Ground Plane and Power Supply Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Ground Plane .......................................................................................................................3
1.2 Power Supply Lines ..............................................................................................................3
1.2.1 Digital and Analog Power Supplies ...................................................................................................................... 3
Chapter 2 Tied Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Unused Pins ........................................................................................................................5
2.2 I²C Pull-up Resistors .............................................................................................................5
Chapter 3 External Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1 PLL .......................................................................................................................................6
3.2 Crystal Oscillator ..................................................................................................................6
Chapter 4 Reference Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Chapter 5 CVBS and HSYNC Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 CVBS Signal on ST92196 ..................................................................................................10
5.2 HSYNC Signal ....................................................................................................................10
Chapter 6 PCB Compatibility between ST92196 and ST92186 MCUs . . . . . . . . . . . . . . . 10
6.1 SDIP56/42 Mounting Instructions .......................................................................................10
6.2 SDIP56/32 Mounting instructions .......................................................................................11
Chapter 7 Developing Applications for ST92186 using ST92x196 . . . . . . . . . . . . . . . . . . 12
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AN2122 Ground Plane and Power Supply Lines
1 Ground Plane and Power Supply Lines
1.1 Ground Plane
A local ground plane must be placed under the entire area of the ST92196/186 component and
connected using the widest possible line to the PCB ground as shown in Figure 1, Figure 2 and
Figure 3. This plane and its associated lines are dedicated to the ST92196/186 microcontroller. It is
strongly recommended not to connect any other lines from components not already connected to
the ST92196/186 to this plane. This is to avoid adding any impedance or analog disturbances which
could cause the IC ground to float.
All ground pins for the ST92196/186 (VSS1 and VSS2) and external components (PLL, oscillator,
etc.) must be connected to this ground plane.
Ground pins VSS1 and VSS2 must be connected as close as possible to each other on the printed
circuit board.
1.2 Power Supply Lines
1.2.1 Digital and Analog Power Supplies
Two different power supply lines are required for the ST92196/186:
● one Analog power supply line for VDDA pin.
● one Digital power supply line (pins VDD1 and VDD2 (only on ST92196)).
Those power supply levels must be within the +5V ±10% range with |VDD-AVDD| < 600 mV.
The supply pins must be decoupled as shown in Figure 1, Figure 2 and Figure 3. Decoupling
capacitors must be set as close as possible to the IC supply pins.
An inductive component, with a low serial resistance, must be placed close to the decoupling
capacitors to provide high impedance and to improve noise filtering. This component is required on
both:
● the VDDA power supply pin to prevent noise disturbances from the PCB power source,
● the VDD power supply pins in order to prevent disturbances being sent towards the PCB power
source and other ICs.
The VDD and VDDA lines must be dedicated to the ST92196/186. Any other connections
between other IC supply pins and VDD and/or VDDA lines are not recommended. This does
not include MCU Reset circuitry. (See Figure 1, Figure 2 and Figure 3).
All other components must be connected to the +5V power supply and not to the ST92196/186 VDD
or VDDA lines.
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Ground Plane and Power Supply Lines AN2122
Figure 1: Ground Plane and Power Supply Lines for ST92196
GND
ST92196
Device
GND Plane
(under device)
+5V
VDD
10uH
VDDA (Other connections not recommended)
10uH
55
56
TEST0
VPP
VSS2
1
Other connections possible
10uF
+
100nF
32
VSS1VDDA
VDD2
16
100nF
10uF
+
10uF
+
100nF
3041 29
VDD1
Note: For ST92196 family devices, there is an internal connection between the VDD1 and VDD2 pins.
Nevertheless, for better current distribution, it is highly advised to externally connect both VDD1 and
VDD2 pins to digital +5V power supply.
Figure 2: Ground Plane and Power Supply Lines for ST92186 SDIP42 Packages
GND
+5V
Other connections possible
VDD
10uH
VDDA (Other connections not recommended)
10uH
10uF
10uF
+
+
ST92186 SDIP42
25
100nF
2334 22
VSS1VDDA
VDD1
Device
42
VSS2
100nF
GND Plane
(under device)
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1
TEST0
2
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AN2122 Tied Pins
Figure 3: Ground Plane and Power Supply Lines for ST92186 SDIP32 Package
GND
+5V
Other connections possible
VDD
10uH
VDDA (Other connections not recommended)
10uH
10uF
10uF
+
+
ST92186 SDIP32
Device
GND Plane
(under device)
32
1
TEST0
2
20
100nF
100nF
18 17
VSS1VDDA
VDD1
2 Tied Pins
2.1 Unused Pins
Table 1: Rules for Connecting Unused Pins
Pin Name Rule
TEST0 Tie to VDD
VPP (only on ST92196) Tie to VDD
Note: All unused I/O pins must be initialized as Bidirectional Weak Pull Up (default state after reset - set
by hardware), associated with a ‘0’ in their data register. This prevents uncontrolled levels and
reduces power consumption.
2.2 I²C Pull-up Resistors
All the pull-up resistors (1.7 kΩ)of the ST92196/186 I²C line must be connected to the +5V power
supply line (and not to the VDDA or VDD pins).
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