cd00292095

AN3320
Application note
Getting started with STM32F20xxx/21xxx MCU
hardware development
Introduction
This application note is intended for system designers who require a hardware
implementation overview of the development board features such as the power supply, the
clock management, the reset control, the boot mode settings and the debug management. It
shows how to use the high-density performance line STM32F20xxx/21xxx product families
and describes the minimum hardware resources required to develop an
STM32F20xxx/21xxx application.
Detailed reference design schematics are also contained in this document with descriptions
of the main components, interfaces and modes.
August 2011
Doc ID 18267 Rev 2
1/29
www.st.com
Contents
AN3320
Contents
1
Power supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1
2
1.1.2
Battery backup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.1.3
Voltage regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3
Reset & power supply supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3.1
Power on reset (POR) / power down reset (PDR) . . . . . . . . . . . . . . . . . . 9
1.3.2
Programmable voltage detector (PVD) . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.3.3
System reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3
2/29
Independent A/D converter supply and reference voltage . . . . . . . . . . . . 7
Power supply schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2
4
1.1.1
1.2
2.1
3
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
HSE OSC clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1.1
External source (HSE bypass) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.2
External crystal/ceramic resonator (HSE crystal) . . . . . . . . . . . . . . . . . 13
LSE OSC clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.1
External source (LSE bypass) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.2
External crystal/ceramic resonator (LSE crystal) . . . . . . . . . . . . . . . . . . 14
Clock security system (CSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Boot configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.1
Boot mode selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2
Boot pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3
Embedded boot loader mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Debug management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.2
SWJ debug port (serial wire and JTAG) . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.3
Pinout and debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.3.1
SWJ debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.3.2
Flexible SWJ-DP pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.3.3
Internal pull-up and pull-down resistors on JTAG pins . . . . . . . . . . . . . . 19
4.3.4
SWJ debug port connection with standard JTAG connector . . . . . . . . . 20
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AN3320
5
6
Contents
Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.1
Printed circuit board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.2
Component position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.3
Ground and power supply (VSS, VDD) . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.4
Decoupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.5
Other signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.6
Unused I/Os and features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Reference design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.1
6.2
7
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.1.1
Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.1.2
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.1.3
Boot mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.1.4
SWJ interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.1.5
Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Component references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
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List of tables
AN3320
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
4/29
Boot modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Debug port pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
SWJ I/O pin availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Mandatory components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Optional components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Reference connection for all packages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Doc ID 18267 Rev 2
AN3320
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Power supply overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Power supply scheme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Power-on reset/power-down reset waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
PVD thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Reset circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
HSE external clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
HSE crystal/ceramic resonators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
LSE external clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
LSE crystal/ceramic resonators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Boot mode selection implementation example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Host-to-board connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
JTAG connector implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Typical layout for VDD/VSS pair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
STM32F207IG(H6) microcontroller reference schematic . . . . . . . . . . . . . . . . . . . . . . . . . . 25
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Power supplies
AN3320
1
Power supplies
1.1
Introduction
The device requires a 1.8 V to 3.6 V operating voltage supply (VDD), excepted the WLCSP
package witch requires 1.65 V to 3.6 V. An embedded regulator is used to supply the
internal 1.2 V digital power.
The real-time clock (RTC) and backup registers can be powered from the VBAT voltage when
the main VDD supply is powered off.
Figure 1.
Power supply overview
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1. VDDA and VSSA must be connected to VDD and VSS, respectively.
2. The voltage on VREF ranges from 1.65 V to VDDA for WLCSP64+2 packages.
6/29
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AN3320
1.1.1
Power supplies
Independent A/D converter supply and reference voltage
To improve conversion accuracy, the ADC has an independent power supply that can be
filtered separately, and shielded from noise on the PCB.
●
the ADC voltage supply input is available on a separate VDDA pin
●
an isolated supply ground connection is provided on the VSSA pin
When available (depending on package), VREF– must be tied to VSSA.
On 100-pin package and above and on WLCSP64+2
To ensure a better accuracy on low-voltage inputs, the user can connect a separate external
reference voltage ADC input on VREF+. The voltage on VREF+ may range from 1.8 V to
VDDA. On WLCSP64+2, the VREF- pin is not available, it is internally connected to the ADC
ground (VSSA).
On 64-pin packages
The VREF+ and VREF- pins are not available, they are internally connected to the ADC
voltage supply (VDDA) and ground (VSSA).
1.1.2
Battery backup
To retain the content of the Backup registers when VDD is turned off, the VBAT pin can be
connected to an optional standby voltage supplied by a battery or another source.
The VBAT pin also powers the RTC unit, allowing the RTC to operate even when the main
digital supply (VDD) is turned off. The switch to the VBAT supply is controlled by the power
down reset (PDR) circuitry embedded in the Reset block.
If no external battery is used in the application, it is highly recommended to connect VBAT
externally to VDD.
1.1.3
Voltage regulator
The voltage regulator is always enabled after reset. It works in three different modes
depending on the application modes.
Note:
●
in Run mode, the regulator supplies full power to the 1.2 V domain (core, memories
and digital peripherals)
●
in Stop mode, the regulator supplies low power to the 1.2 V domain, preserving the
contents of the registers and SRAM
●
in Standby mode, the regulator is powered down. The contents of the registers and
SRAM are lost except for those concerned with the Standby circuitry and the Backup
domain.
Depending on the selected package, there are specific pins that should be connected either
to VSS or VDD to activate or deactivate the voltage regulator. Refer to section "Voltage
regulator" in STM32F20xxx/21xxx datasheet for details.
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Power supplies
1.2
AN3320
Power supply schemes
The circuit is powered by a stabilized power supply, VDD.
●
Caution:
–
8/29
The VDD voltage range is 1.8 V to 3.6 V (and 1.65 V to 3.6 V for WLCSP64+2
package)
●
The VDD pins must be connected to VDD with external decoupling capacitors: one
single Tantalum or Ceramic capacitor (min. 4.7 µF typ.10 µF) for the package + one
100 nF Ceramic capacitor for each VDD pin.
●
The VBAT pin can be connected to the external battery (1.65 V < VBAT < 3.6 V). If no
external battery is used, it is recommended to connect this pin to VDD with a 100 nF
external ceramic decoupling capacitor.
●
The VDDA pin must be connected to two external decoupling capacitors (100 nF
Ceramic + 1 µF Tantalum or Ceramic).
●
The VREF+ pin can be connected to the VDDA external power supply. If a separate,
external reference voltage is applied on VREF+, a 100 nF and a 1 µF capacitors must be
connected on this pin. In all cases, VREF+ must be kept between 1.65 V and VDDA.
●
Additional precautions can be taken to filter analog noise:
–
VDDA can be connected to VDD through a ferrite bead.
–
The VREF+ pin can be connected to VDDA through a resistor (typ. 47 Ω).
●
For the voltage regulator configuration, there are specific pins (REGOFF and IRROFF
depending on the package) that should be connected either to VSS or VDD to activate
or deactivate the voltage regulator specific. Refer to section "Voltage regulator" in
STM32F20xxx/21xxx datasheet for details.
●
When the voltage regulator is enabled, VCAP1 and VCAP2 pins must be connected to
2*2.2 µF Ceramic capacitor.
Doc ID 18267 Rev 2
AN3320
Power supplies
Figure 2.
Power supply scheme
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1. Optional. If a separate, external reference voltage is connected on VREF+, the two capacitors (100 nF and
1 µF) must be connected.
2. VREF+ is either connected to VREF or to VDDA.
3. N is the number of VDD and VSS inputs.
4. Refer to section "Voltage regulator" in STM32F20xxx/21xxx datasheet to connect REGOFF and IRROFF
pins.
1.3
Reset & power supply supervisor
1.3.1
Power on reset (POR) / power down reset (PDR)
The device has an integrated POR/PDR circuitry that allows proper operation starting from
1.8 V.
The device remains in the Reset mode as long as VDD is below a specified threshold,
VPOR/PDR, without the need for an external reset circuit. For more details concerning the
power on/power down reset threshold, refer to the electrical characteristics in
STM32F20xxx/21xxx datasheets.
On WLCSP66 package if IRROFF pin is set to VDD (in that case REGOFF pin must not be
activated, refer to section "Voltage regulator" in STM32F20xxx/21xxx datasheet for details ),
the PDR is not functional. Then the VDD can lower below 1.8 V, but the external circuitry
must ensure that reset pin is activated when VDD/VDDA becomes below 1.65 V.
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Power supplies
AN3320
Figure 3.
Power-on reset/power-down reset waveform
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1. tRSTTEMPO is approximately 2.6 ms. VPOR/PDR rising edge is 1.74 V (typ.) and VPOR/PDR falling edge is
1.70 V (typ.). Refer to STM32F20xxx/21xxx datasheets for actual value.
1.3.2
Programmable voltage detector (PVD)
You can use the PVD to monitor the VDD power supply by comparing it to a threshold
selected by the PLS[2:0] bits in the Power control register (PWR_CR).
The PVD is enabled by setting the PVDE bit.
A PVDO flag is available, in the Power control/status register (PWR_CSR), to indicate
whether VDD is higher or lower than the PVD threshold. This event is internally connected to
EXTI Line16 and can generate an interrupt if enabled through the EXTI registers. The PVD
output interrupt can be generated when VDD drops below the PVD threshold and/or when
VDD rises above the PVD threshold depending on the EXTI Line16 rising/falling edge
configuration. As an example the service routine can perform emergency shutdown tasks.
Figure 4.
PVD thresholds
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FALLINGEDGE
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10/29
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AN3320
1.3.3
Power supplies
System reset
A system reset sets all registers to their reset values except for the reset flags in the clock
controller CSR register and the registers in the Backup domain (see Figure 1).
A system reset is generated when one of the following events occurs:
1.
A low level on the NRST pin (external reset)
2.
window watchdog end-of-count condition (WWDG reset)
3.
Independent watchdog end-of-count condition (IWDG reset)
4.
A software reset (SW reset)
5.
Low-power management reset
The reset source can be identified by checking the reset flags in the Control/Status register,
RCC_CSR.
The STM32F20xxx/21xxx does not require an external reset circuit to power-up correctly.
Only a pull-down capacitor is recommended to improve EMS performance by protecting the
device against parasitic resets. See Figure 5.
Charging and discharging a pull-down capacitor through an internal resistor increases the
device power consumption. The capacitor recommended value (100 nF) can be reduced to
10 nF to limit this power consumption;
Figure 5.
Reset circuit
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Clocks
2
AN3320
Clocks
Three different clock sources can be used to drive the system clock (SYSCLK):
●
HSI oscillator clock (high-speed internal clock signal)
●
HSE oscillator clock (high-speed external clock signal)
●
PLL clock
The devices have two secondary clock sources:
●
32 kHz low-speed internal RC (LSI RC) that drives the independent watchdog and,
optionally, the RTC used for Auto-wakeup from the Stop/Standby modes.
●
32.768 kHz low-speed external crystal (LSE crystal) that optionally drives the real-time
clock (RTCCLK)
Each clock source can be switched on or off independently when it is not used, to optimize
the power consumption.
Refer to the STM32F20xxx/21xxx reference manual RM0033 for the description of the clock
tree.
2.1
HSE OSC clock
The high-speed external clock signal (HSE) can be generated from two possible clock
sources:
●
HSE external crystal/ceramic resonator (see Figure 7)
●
HSE user external clock (see Figure 6)
Figure 6.
HSE external clock
Figure 7.
HSE crystal/ceramic
resonators
(ARDWARECONFIGURATION
34-&
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/3#?).
OSC_IN
/3#?/54
OSC_OUT
2%84
(Hi-Z)
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ai14369
#,
#,
AIA
1. The value of REXT depends on the crystal characteristics. Typical value is in the range of 5 to 6 RS
(resonator series resistance).
2. Load capacitance CL has the following formula: CL = CL1 x CL2 / (CL1 + CL2) + Cstray where: Cstray is the pin
capacitance and board or trace PCB-related capacitance. Typically, it is between 2 pF and 7 pF. Please
refer to Section 5: Recommendations on page 21 to minimize its value.
12/29
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AN3320
2.1.1
Clocks
External source (HSE bypass)
In this mode, an external clock source must be provided. It can have a frequency from 1 to
16 MHz (refer to STM32F20xxx/21xxx datasheets for actual max value).
The external clock signal (square, sine or triangle) with a duty cycle of about 50%, has to
drive the OSC_IN pin while the OSC_OUT pin must be left in the high impedance state (see
Figure 7 and Figure 6).
2.1.2
External crystal/ceramic resonator (HSE crystal)
The external oscillator frequency ranges from 4 to 26 MHz.
The external oscillator has the advantage of producing a very accurate rate on the main
clock. The associated hardware configuration is shown in Figure 7. Using a 25 MHz
oscillator frequency is a good choice to get accurate Ethernet, USB OTG high-speed
peripheral, and I2S.
The resonator and the load capacitors have to be connected as close as possible to the
oscillator pins in order to minimize output distortion and startup stabilization time. The load
capacitance values must be adjusted according to the selected oscillator.
For CL1 and CL2 it is recommended to use high-quality ceramic capacitors in the 5 pF-to25 pF range (typ.), designed for high-frequency applications and selected to meet the
requirements of the crystal or resonator. CL1 and CL2, are usually the same value. The
crystal manufacturer typically specifies a load capacitance that is the series combination of
CL1 and CL2. The PCB and MCU pin capacitances must be included when sizing CL1 and
CL2 (10 pF can be used as a rough estimate of the combined pin and board capacitance).
Refer to the electrical characteristics sections in the datasheet of your product for more
details.
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Clocks
2.2
AN3320
LSE OSC clock
The low-speed external clock signal (LSE) can be generated from two possible clock
sources:
●
LSE external crystal/ceramic resonator (see Figure 9)
●
LSE user external clock (see Figure 8)
Figure 8.
LSE external clock
Figure 9.
LSE crystal/ceramic
resonators
(ARDWARECONFIGURATION
34-&
Hardware configuration
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OSC32_IN OSC32_OUT
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AID
1. “LSE crystal/ceramic resonators” figure:
To avoid exceeding the maximum value of CL1 and CL2 (15 pF) it is strongly recommended to use a
resonator with a load capacitance CL ≤ 7 pF. Never use a resonator with a load capacitance of 12.5 pF.
2. “LSE external clock” and “LSE crystal/ceramic resonators” figures:
OSC32_IN and OSC32_OUT pins can be used also as GPIO, but it is recommended not to use them as
both RTC and GPIO pins in the same application.
3. “LSE crystal/ceramic resonators” figure:
The value of REXT depends on the crystal characteristics. A 0 Ω resistor would work but would not be
optimal. To fine tube RS value, refer to AN2867 - Oscillator design guide for ST microcontrollers.
2.2.1
External source (LSE bypass)
In this mode, an external clock source must be provided. It can have a frequency of up to
1 MHz. The external clock signal (square, sine or triangle) with a duty cycle of about 50%
has to drive the OSC32_IN pin while the OSC32_OUT pin must be left high impedance (see
Figure 8).
2.2.2
External crystal/ceramic resonator (LSE crystal)
The LSE crystal is a 32.768 kHz low-speed external crystal or ceramic resonator. It has the
advantage of providing a low-power, but highly accurate clock source to the real-time clock
peripheral (RTC) for clock/calendar or other timing functions.
The resonator and the load capacitors have to be connected as close as possible to the
oscillator pins in order to minimize output distortion and startup stabilization time. The load
capacitance values must be adjusted according to the selected oscillator.
14/29
Doc ID 18267 Rev 2
AN3320
2.3
Clocks
Clock security system (CSS)
The clock security system can be activated by software. In this case, the clock detector is
enabled after the HSE oscillator startup delay, and disabled when this oscillator is stopped.
●
If a failure is detected on the HSE oscillator clock, the oscillator is automatically
disabled. A clock failure event is sent to the break input of the TIM1 advanced control
timer and an interrupt is generated to inform the software about the failure (clock
security system interrupt CSSI), allowing the MCU to perform rescue operations. The
CSSI is linked to the Cortex™-M3 NMI (non-maskable interrupt) exception vector.
●
If the HSE oscillator is used directly or indirectly as the system clock (indirectly means
that it is used as the PLL input clock, and the PLL clock is used as the system clock), a
detected failure causes a switch of the system clock to the HSI oscillator and the
disabling of the external HSE oscillator. If the HSE oscillator clock (divided or not) is the
clock entry of the PLL used as system clock when the failure occurs, the PLL is
disabled too.
For details, see the STM32F20xxx/21xxx (RM0033) reference manuals available from the
STMicroelectronics website www.st.com.
Doc ID 18267 Rev 2
15/29
Boot configuration
AN3320
3
Boot configuration
3.1
Boot mode selection
In the STM32F20xxx/21xxx, three different boot modes can be selected by means of the
BOOT[1:0] pins as shown in Table 1.
Table 1.
Boot modes
BOOT mode selection pins
Boot mode
Aliasing
BOOT1
BOOT0
x
0
Main Flash memory
Main Flash memory is selected as boot
space
0
1
System memory
System memory is selected as boot
space
1
1
Embedded SRAM
Embedded SRAM is selected as boot
space
The values on the BOOT pins are latched on the 4th rising edge of SYSCLK after a reset. It
is up to the user to set the BOOT1 and BOOT0 pins after reset to select the required boot
mode.
The BOOT pins are also resampled when exiting the Standby mode. Consequently, they
must be kept in the required Boot mode configuration in the Standby mode. After this startup
delay has elapsed, the CPU fetches the top-of-stack value from address 0x0000 0000, and
starts code execution from the boot memory starting from 0x0000 0004.
3.2
Boot pin connection
Figure 10 shows the external connection required to select the boot memory of the
STM32F20xxx/21xxx.
Figure 10. Boot mode selection implementation example
34-&
6$$
KΩ
6$$
"//4
KΩ
"//4
AIB
1. Resistor values are given only as a typical example.
16/29
Doc ID 18267 Rev 2
AN3320
3.3
Boot configuration
Embedded boot loader mode
The Embedded boot loader mode is used to reprogram the Flash memory using one of the
available serial USART1(PA9/PA10), USART3(PB10/11 & PC10/11), CAN2(PB5/13) or USB
OTG FS(PA11/12) in Device mode (DFU: device firmware upgrade).
The USART peripheral operates with the internal 16 MHz oscillator (HSI). The CAN and
USB OTG FS, however, can only function if an external clock (HSE) multiple of 1 MHz
(between 4 and 26 MHz)is present.
This embedded boot loader is located in the System memory and is programmed by ST
during production.
For additional information, refer to AN2606.
Doc ID 18267 Rev 2
17/29
Debug management
AN3320
4
Debug management
4.1
Introduction
The Host/Target interface is the hardware equipment that connects the host to the
application board. This interface is made of three components: a hardware debug tool, a
JTAG or SW connector and a cable connecting the host to the debug tool.
Figure 11 shows the connection of the host to the evaluation board STM3220G-EVAL.
Figure 11. Host-to-board connection
$EBUGTOOL
(OST0#
*4!'37CONNECTOR
0OWERSUPPLY
%VALUATIONBOARD
AIB
4.2
SWJ debug port (serial wire and JTAG)
The STM32F20xxx/21xxx core integrates the serial wire / JTAG debug port (SWJ-DP). It is
an ARM® standard CoreSight™ debug port that combines a JTAG-DP (5-pin) interface and
a SW-DP (2-pin) interface.
●
The JTAG debug port (JTAG-DP) provides a 5-pin standard JTAG interface to the AHPAP port
●
The serial wire debug port (SW-DP) provides a 2-pin (clock + data) interface to the
AHP-AP port
In the SWJ-DP, the two JTAG pins of the SW-DP are multiplexed with some of the five JTAG
pins of the JTAG-DP.
4.3
Pinout and debug port pins
The STM32F20xxx/21xxx MCU is offered in various packages with different numbers of
available pins. As a result, some functionality related to the pin availability may differ from
one package to another.
4.3.1
SWJ debug port pins
Five pins are used as outputs for the SWJ-DP as alternate functions of general-purpose
I/Os (GPIOs). These pins, shown in Table 2, are available on all packages.
18/29
Doc ID 18267 Rev 2
AN3320
Debug management
Table 2.
Debug port pin assignment
JTAG debug port
SW debug port
Type
Type Debug assignment
Pin
assignment
SWJ-DP pin name
4.3.2
Description
JTMS/SWDIO
I
JTAG test mode
selection
I/O
Serial wire data
input/output
PA13
JTCK/SWCLK
I
JTAG test clock
I
Serial wire clock
PA14
JTDI
I
JTAG test data input
-
-
PA15
JTDO/TRACESWO
O
JTAG test data output
-
TRACESWO if async trace
PB3
is enabled
JNTRST
I
JTAG test nReset
-
-
PB4
Flexible SWJ-DP pin assignment
After reset (SYSRESETn or PORESETn), all five pins used for the SWJ-DP are assigned as
dedicated pins immediately usable by the debugger host (note that the trace outputs are not
assigned except if explicitly programmed by the debugger host).
However, some of the JTAG pins shown in Table 3 can be configured to an alternate function
through the GPIOx_AFRx registers.
Table 3.
SWJ I/O pin availability
SWJ I/O pin assigned
PA13 /
JTMS/
SWDIO
PA14 /
JTCK/
SWCLK
PA15 /
JTDI
PB3 /
JTDO
PB4/
JNTRST
Full SWJ (JTAG-DP + SW-DP) - reset state
X
X
X
X
X
Full SWJ (JTAG-DP + SW-DP) but without
JNTRST
X
X
X
X
JTAG-DP disabled and SW-DP enabled
X
X
Available Debug ports
JTAG-DP disabled and SW-DP disabled
Released
Table 3 shows the different possibilities to release some pins.
For more details, see the STM32F20xxx/21xxx (RM0033) reference manual, available from
the STMicroelectronics website www.st.com.
4.3.3
Internal pull-up and pull-down resistors on JTAG pins
The JTAG input pins must not be floating since they are directly connected to flip-flops to
control the debug mode features. Special care must be taken with the SWCLK/TCK pin that
is directly connected to the clock of some of these flip-flops.
Doc ID 18267 Rev 2
19/29
Debug management
AN3320
To avoid any uncontrolled I/O levels, the STM32F20xxx/21xxx embeds internal pull-up and
pull-down resistors on JTAG input pins:
●
JNTRST: Internal pull-up
●
JTDI: Internal pull-up
●
JTMS/SWDIO: Internal pull-up
●
TCK/SWCLK: Internal pull-down
Once a JTAG I/O is released by the user software, the GPIO controller takes control again.
The reset states of the GPIO control registers put the I/Os in the equivalent state:
●
JNTRST: Input pull-up
●
JTDI: Input pull-up
●
JTMS/SWDIO: Input pull-up
●
JTCK/SWCLK: Input pull-down
●
JTDO: Input floating
The software can then use these I/Os as standard GPIOs.
Note:
The JTAG IEEE standard recommends to add pull-up resistors on TDI, TMS and nTRST but
there is no special recommendation for TCK. However, for the STM32F20xxx/21xxx, an
integrated pull-down resistor is used for JTCK.
Having embedded pull-up and pull-down resistors removes the need to add external
resistors.
4.3.4
SWJ debug port connection with standard JTAG connector
Figure 12 shows the connection between the STM32F20xxx/21xxx and a standard JTAG
connector.
Figure 12. JTAG connector implementation
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*34-37$)/
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KΩ
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633
AIB
20/29
Doc ID 18267 Rev 2
AN3320
Recommendations
5
Recommendations
5.1
Printed circuit board
For technical reasons, it is best to use a multilayer printed circuit board (PCB) with a
separate layer dedicated to ground (VSS) and another dedicated to the VDD supply. This
provides good decoupling and a good shielding effect. For many applications, economical
reasons prohibit the use of this type of board. In this case, the major requirement is to
ensure a good structure for ground and for the power supply.
5.2
Component position
A preliminary layout of the PCB must separate the different circuits according to their EMI
contribution in order to reduce cross-coupling on the PCB, that is noisy, high-current circuits,
low-voltage circuits, and digital components.
5.3
Ground and power supply (VSS, VDD)
Every block (noisy, low-level sensitive, digital, etc.) should be grounded individually and all
ground returns should be to a single point. Loops must be avoided or have a minimum area.
The power supply should be implemented close to the ground line to minimize the area of
the supply loop. This is due to the fact that the supply loop acts as an antenna, and is
therefore the main transmitter and receiver of EMI. All component-free PCB areas must be
filled with additional grounding to create a kind of shielding (especially when using singlelayer PCBs).
5.4
Decoupling
All power supply and ground pins must be properly connected to the power supplies. These
connections, including pads, tracks and vias should have as low impedance as possible.
This is typically achieved with thick track widths and, preferably, the use of dedicated power
supply planes in multilayer PCBs.
In addition, each power supply pair should be decoupled with filtering Ceramic capacitors C
(100 nF) and one single Tantalum or Ceramic capacitor (min. 4.7 µF typ.10 µF) connected in
parallel on the STM32F20xxx/21xxx device. These capacitors need to be placed as close as
possible to, or below, the appropriate pins on the underside of the PCB. Typical values are
10 nF to 100 nF, but exact values depend on the application needs. Figure 13 shows the
typical layout of such a VDD/VSS pair.
Doc ID 18267 Rev 2
21/29
Recommendations
AN3320
Figure 13. Typical layout for VDD/VSS pair
Via to VDD
Via to VSS
Cap.
VDD VSS
STM32F20xxx/21xxx
5.5
Other signals
When designing an application, the EMC performance can be improved by closely studying:
5.6
●
Signals for which a temporary disturbance affects the running process permanently
(the case of interrupts and handshaking strobe signals, and not the case for LED
commands).
For these signals, a surrounding ground trace, shorter lengths and the absence of
noisy and sensitive traces nearby (crosstalk effect) improve EMC performance.
For digital signals, the best possible electrical margin must be reached for the two
logical states and slow Schmitt triggers are recommended to eliminate parasitic states.
●
Noisy signals (clock, etc.)
●
Sensitive signals (high impedance, etc.)
Unused I/Os and features
All microcontrollers are designed for a variety of applications and often a particular
application does not use 100% of the MCU resources.
To increase EMC performance, unused clocks, counters or I/Os, should not be left free, e.g.
I/Os should be set to “0” or “1”(pull-up or pull-down to the unused I/O pins.) and unused
features should be “frozen” or disabled.
22/29
Doc ID 18267 Rev 2
AN3320
Reference design
6
Reference design
6.1
Description
The reference design shown in Figure 14, is based on the STM32F207IF(H6), a highly
integrated microcontroller running at 120 MHz, that combines the Cortex™-M3 32-bit RISC
CPU core with 1 Mbyte of embedded Flash memory and up to 128 + 4 Kbytes of high-speed
SRAM.
This reference design can be tailored to any other STM32F20xxx/21xxx device with different
package, using the pins correspondence given in Table 6: Reference connection for all
packages.
6.1.1
Clock
Two clock sources are used for the microcontroller:
●
LSE: X1– 32.768 kHz crystal for the embedded RTC
●
HSE: X2– 25 MHz crystal for the STM32F20xxx/21xxx microcontroller
Refer to Section 2: Clocks on page 12.
6.1.2
Reset
The reset signal in Figure 14 is active low. The reset sources include:
●
Reset button (B1)
●
Debugging tools via the connector CN1
Refer to Section 1.3: Reset & power supply supervisor on page 9.
6.1.3
Boot mode
The boot option is configured by setting switches SW2 (Boot 0) and SW1 (Boot 1). Refer to
Section 3: Boot configuration on page 16.
Note:
In low-power mode (more specially in Standby mode) the boot mode is mandatory to be
able to connect to tools (the device should boot from the SRAM).
6.1.4
SWJ interface
The reference design shows the connection between the STM32F20xxx/21xxx and a
standard JTAG connector. Refer to Section 4: Debug management on page 18.
Note:
It is recommended to connect the reset pins so as to be able to reset the application from
the tools.
6.1.5
Power supply
Refer to Section 1: Power supplies on page 6.
Doc ID 18267 Rev 2
23/29
Reference design
6.2
AN3320
Component references
Table 4.
Mandatory components
Id Components name
Reference
Quantity
1 Microcontroller
STM32F207IG(H6)
1
176-pin package
2 Capacitors
100 nF
16
Ceramic capacitors (decoupling
capacitors)
3 Capacitor
10 µF
1
Ceramic capacitor (decoupling capacitor)
Table 5.
Optional components
Id Components name
1
2
24/29
Comments
Resistor
Resistor
Reference
10 kΩ
390 Ω
Quantity
Comments
5
pull-up and pull-down for JTAG and Boot mode.
1
Used for HSE: the value depends on the
crystal characteristics.
This resistor value is given only as a typical
example.
3
Resistor
0Ω
1
Used for LSE: the value depends on the crystal
characteristics.
This resistor value is given only as a typical
example.
4
Capacitor
100 nF
2
Ceramic capacitor.
5
Capacitor
2 pF
2
Used for LSE: the value depends on the crystal
characteristics.
6
Capacitor
1 µF
2
Used for VDDA and VREF.
7
Capacitor
2.2 µF
2
Used for internal regulator when it is on.
8
Capacitor
20 pF
2
Used for HSE: the value depends on the
crystal characteristics.
9
Quartz
25 MHz
1
Used for HSE.
10
Quartz
32 kHz
1
Used for LSE.
11
JTAG connector
HE10
1
12
Transil diode
5 V-400 W
11
For JTAG protection.
13
Resistor
22 Ohm
11
For JTAG protection.
14
Battery
3V3
1
If no external battery is used in the application,
it is recommended to connect VBAT externally
to VDD.
15
Switch
3V3
2
Used to select the right boot mode.
16
Push-button
B1
1
17
Jumper
3 pins
2
Used to select VBAT source, and REGOFF pin.
18
Debug trace
connector
FTSH-11001-L-DV
1
Used for JTAG/SWD and debug trace.
Doc ID 18267 Rev 2
Doc ID 18267 Rev 2
CN2
FTSH-110-01-L-DV
+3V3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
R10 10K
R9 10K
R16 22
R15 22
R14 22
R13 22
R12 22
KEY
22
22
22
22
22
22
Z5V1
Z5V1
Z5V1
Z5V1
Z5V1
C23
20pF
25MHz
X1
C24
20pF
R17
390
Z5V1
Z5V1
3
4
100nF
C27
RESET
2
Ref TBD
B1
1
4
3
1
X2
TRACE_D3
TRACE_D2
TRACE_D1
TRACE_D0
2
R11
09.03290.01
C26
2pF
R19
0
3
+3V3
1 SW1
TRST
TDI
JP4
BAT60JFILM
D13
+3V3
E1
F1
PC14
PC15
NRST
BOOT0
PC14
PC15
PH0
PH1
PD0
PD1
PD2
PD3
PD4
PD5
PD6
PD7
PD8
PD9
PD10
PD11
PD12
PD13
PD14
PD15
PC0
PC1
PC2
PC3
PC4
PC5
PC6
PC7
PC8
PC9
PC10
PC11
PC12
PC13
PB0
PB1
PB2
PB3
PB4
PB5
PB6
PB7
PB8
PB9
PB10
PB11
PB12
PB13
PB14
PB15
PA0
PA1
PA2
PA3
PA4
PA5
PA6
PA7
PA8
PA9
PA10
PA11
PA12
PA13
PA14
PA15
PI11
PI10
PI9
PI8
PI7
PI6
PI5
PI4
PI3
PI2
PI1
PI0
PH15
PH14
PH13
PH12
PH11
PH10
PH9
PH8
PH7
PH6
PH5
PH4
PH3
PH2
PG15
PG14
PG13
PG12
PG11
PG10
PG9
PG8
PG7
PG6
PG5
PG4
PG3
PG2
PG1
PG0
PF15
PF14
PF13
PF12
PF11
PF10
PF9
PF8
PF7
PF6
PF5
PF4
PF3
PF2
PF1
PF0
PE15
PE14
PE13
PE12
PE11
PE10
PE9
PE8
PE7
PE6
PE5
PE4
PE3
PE2
PE1
PE0
STM32F207IGH6
STM32F217IGH6
Bootloader_RESET
Bootloader_BOOT0
D12
BAT60JFILM
JP3
J1
BOOT0 D6
G1
H1
B12
C12
D12
D11
D10
C11
B11
A11
P15
P14
N15
N14
N13
M15
M14
L14
M2
M3
M4
M5
N5
P5
H15
G15
G14
F14
B14
B13
A12
D1
R5
R4
M6
A10
A9
A6
B6
B5
A5
B4
R12
R13
P12
P13
R14
R15
PH0
PH1
BOOT1 PB2
PB3
PB4
SW2
09.03290.01
R20
10K
10K
TDO/SWO
TMS/SWDIO
TCK/SWCLK
TRACE_CK
C25 2
2pF
R18
0
D7 D8 D9 D10 D11
R8
R7
Z5V1
10K
R6
R4
R3
R1
Z5V1
Z5V1
D1 D2 D3 D4 D5 D6
Z5V1
U1A
E4
E3
D3
D2
C2
C3
C4
D4
C13
C14
D14
E14
D13
E13
E12
K12
L12
L13
M13
M12
N12
M11
J4
H4
G4
F4
B7
A7
A8
B8
B9
B10
C10
H14
J14
J15
K13
K14
K15
L15
M7
N7
P7
R7
N6
P6
R6
L1
L2
L3
K1
K2
K3
J3
J2
H2
H3
E2
R11
P11
N11
R10
P10
R9
P9
P8
R8
B3
B2
B1
A1
A2
A3
A4
TRACE_D3
TRACE_D2
TRACE_D1
TRACE_D0
TRACE_CK
VDDA
C1
1μF
C16
10μF
C3
1μF
0
R2
C4
100nF
VREF+
L1
BEAD TP1
VREF
VDD_MCU
CR1220 holder
BT1
SB2
+1V2 +1V2
C5
SB1
2.2uF
L4
C6
M1
F13
M10
F2
G2
M8
M9
H12
G12
F12
D9
D8
D7
D5
N1
VDD_MCU
STM32F207IGH6
VDD_SA
VDD
VSS
VDD
VSS
VDD
VSS
VDD
VSS
VDD
VSS
VSS
VDD
VDD
VSS
VDD
VSS
VDD
VSS
VDD
VSS
VDD VSS_SA
VDD VREFVDD
REGOFF
RFU
VREF+ VSSA
VDDA VCAP
VBAT VCAP
U1B
+3V3
C6
2.2uF
1
3
JP1
2
C17
C20
C18
C19
C21
C22
100nF 100nF 100nF 100nF 100nF 100nF
VDD_MCU
C8
C11
C14
C15
C9
C10
C12
C13
100nF 100nF 100nF 100nF 100nF 100nF 100nF 100nF
+3V3
C7
100nF
JP2
P1
R1
C1
C5
C7
C8
C9
G13
H13
J13
C2
100nF J12
N10
N8
N9
K4
F3
G3
VDD_MCU
2
R5
JTAG connector
+3V3
2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
1
1
N3
N2
P2
R2
N4
P4
P3
R3
F15
E15
D15
C15
B15
PA13 A15
PA14 A14
PA15 A13
3
CN1
JTAG
3
AN3320
Reference design
Figure 14. STM32F207IG(H6) microcontroller reference schematic
!)
2. To be able to reset the device from the tools this resistor has to be kept.
1. If no external battery is used in the application, it is recommended to connect VBAT externally to VDD.
25/29
Reference design
Table 6.
AN3320
Reference connection for all packages
Pin numbers for LQFP packages
Pin name
26/29
Pin
numbers
for BGA
package
Pin numbers for
WLCSP package
176 pins
144 pins
100 pins
64 pins
176 pins
64+2 pins
OSC_IN
29
23
12
5
G1
E9
OSC_OUT
30
24
13
6
H1
F9
PC15OSC32_OUT
10
9
9
4
F1
C9
PC14OSC32_IN
9
8
8
3
E1
B9
BOOT0
166
138
94
60
D6
B6
PB2-BOOT1
58
48
37
28
M6
J4
NRST
31
25
14
7
J1
E8
PA13
124
105
72
46
A15
B2
PA14
137
109
76
49
A14
A1
PA15
138
110
77
50
A13
A2
PB4
162
134
90
56
A9
B4
PB3
161
133
89
55
A10
A4
VCAP_1
81
71
49
31
M10
J3
VCAP_2
125
106
73
47
F13
C2
VSS_2
126
107
74
-
F12
B1
VSS_3
-
-
-
63
-
D8
VSS_4
48
38
27
18
-
F1
VSS_5
22
16
10
-
G2
H9
VSS_6
61
51
-
-
M8
-
VSS_7
71
61
-
-
M9
-
VSS_8
102
83
-
-
-
-
VSS_9
113
94
-
-
G12
-
VSS_10
148
120
-
-
D8
-
VSS_11
158
130
-
-
D7
-
VSS_13
14
-
-
-
F2
-
VSS_14
90
-
-
-
H12
-
VSS_15
135
-
-
-
D9
-
VDD_1
82
72
50
32
N10
-
VDD_2
127
108
75
48
G13
A8
VDD_3
172
144
100
64
C5
D9
Doc ID 18267 Rev 2
AN3320
Reference design
Table 6.
Reference connection for all packages (continued)
Pin numbers for LQFP packages
Pin name
Pin
numbers
for BGA
package
Pin numbers for
WLCSP package
176 pins
144 pins
100 pins
64 pins
176 pins
64+2 pins
VDD_4
49
39
28
19
K4
E1
VDD_5
23
17
11
-
G3
-
VDD_6
62
52
-
-
N8
-
VDD_7
72
62
-
-
N9
-
VDD_8
103
84
-
-
J13
-
VDD_9
114
95
-
-
H13
-
VDD_10
149
121
-
-
C8
-
VDD_11
159
131
-
-
C7
-
VDD_12
36
30
19
-
-
-
VDD_13
15
-
-
-
F3
-
VDD_14
91
-
-
-
J12
-
VDD_15
136
-
-
-
C9
-
VREF+
38
32
21
-
P1
F7
VREF-
-
-
-
-
N1
-
VSS
-
-
-
-
D5
-
VSSA
37
31
20
12
M1
-
VDDA
39
33
22
13
R1
-
VBAT
6
6
6
1
C1
A9
REGOFF
-
-
-
-
L4
H7
IRROFF
-
-
-
-
-
C8
Doc ID 18267 Rev 2
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Revision history
7
AN3320
Revision history
Table 7.
Document revision history
Date
Revision
25-Feb-2011
1
Initial release.
2
Updated REGOFF and IRROFF pin configuration.
Updated standby mode in Chapter 1.1.3: Voltage regulator.
Updated voltage regulator configuration in Chapter 1.2: Power
supply schemes.
Updated frequence of external clock (HSE) in Chapter 3.3:
Embedded boot loader mode section.
22-Aug-2011
28/29
Changes
Doc ID 18267 Rev 2
AN3320
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