Freescale Semiconductor
Advance Information
Document Number: MC33789
Rev. 1.0, 2/2011
Airbag System Basis Chip (SBC)
with Power Supply and PSI5
Sensor Interface
The 33789 is a mixed signal IC for airbag safety applications. The
33789 provides a cost effective and flexible system IC solution across
the range of airbag partitions used in cars and other vehicles.
The 33789 connects to the 12 V vehicle battery and supplies the
multiple voltages of a typical airbag system. The 33789 can detect
switched input states, communicate with both local and remote crash
sensors. It offers an industry standard interface (SPI) and four PSI5
master interfaces. The 33789 has a dedicated safing state machine that
complements the airbag’s MCU hardware/software safing approach.
Also included are a diagnostic - self protection capability and a
programmable analog interface accessible by the system MCU.
The 33789 is well suited for use in low to high end airbag systems by
allowing the designer to scale a design for the number of firing loops
needed while providing enhanced safety and system reliability.
Features
• Designed to operate 5.2 V
≤
V
PWR
≤
20 V, up to a 40 V transient
• Safing state machine with programmable sensing thresholds
• Two configurable high side/low side drivers with PWM capability
• Four PSI5 satellite sensor master interfaces
• Self-protected and diagnostic capability
• Watchdog and system Power ON Reset (POR)
• Supports complete airbag system power supply architecture,
including system power mode control, supplies for squib firing
(33 V), satellite sensors (6.3 V), and local ECU sensors and ECU
logic circuits (5.0 V)
• Nine configurable switch input monitors for simple switch and Hall-
effect sensor interfaces with internal power supply
• 16-bit SPI interface
• LIN 2.1 physical layer interface
V
BAT
33789
AUTO RESTRAINT
AE SUFFIX (PB-FREE)
EXPOSED PAD
98ASA10763D
64-PIN LQFP
ORDERING INFORMATION
Device
MCZ33789AE/R2
Temperature
Range (T
A
)
-40 to 125 °C
Package
64 LQFP EP
33789
IN1
IN2
WAKE
VPWR
BSTSW
VBST
VER
ERSW
Wake Up
9 Input
Monitors
V
BAT
IN8
IN9
LIN
PSI5_1
33 V
4 Satellite
Sensor
Interfaces
PSI5_2
PSI5_3
PSI5_4
V
PWR
Energy
Storage
5.0 V
5.0 V
VFIRE_x
SQB_H1
OUT1_D
OUT1_S
BUCKSW
VBUCK
VCCDRI
9.0 V
5.0 V
Output
Squib
Driver 1
SQB_H1
5.0 V
X/Y Axis
Accel.
Sensor
5.0 V
SPI_A
VDD AIN
Sensor SPI
SPI
Squib
Driver 2
VCC
SQB_L1
SQB_L1
AOUT
RESET
ARM
FEN_1
FEN_2
Cross-coupled
Squib
Connections
RESET
SPI_B
Squib Driver SPI
2 ARM_X and ARM_Y for Squib Driver 2 FENs
RESET
SPI
MCU
Figure 1. 33789 Simplified Application Diagram
* This document contains certain information on a new product.
Specifications and information herein are subject to change without notice.
© Freescale Semiconductor, Inc., 2010-2011. All rights reserved.
INTERNAL BLOCK DIAGRAM
INTERNAL BLOCK DIAGRAM
SI
SO
SCK
CS
CS_A
CS_B
CS_C
A_SENSOR
ARM
DISARM
ASST
SCRAP
OUT1_D
OUT1_S
OUT2_D
OUT2_S
CLK
SATSYNC
PSI5_1
PSI5_2
PSI5_3
PSI5_4
GND_PSI
IN1
IN2
IN3
IN4
IN5
IN6
IN7
IN8
IN9
AOUT
Analog Multiplexer
Analog Multiplexer
Analog
Multiplexer
Safing
Logic
SPI
Monitor
SPI
Interface
Power Mode
Control
V
REF
WAKE
VPWR
BSTSW
Boost
Converter
Safing
BSTGND
VBST
BSTCOMP1
BSTCOMP2
Configurable
Drivers
Energy
Reserve
Control
VER
ERSW
VERDIAG
VBUCK
PSI5
Satellite
Sensor
Interfaces
Buck
Converter
BUCKSW
BUCKGND
VBUCK_R
BUCKCOMP1
BUCKCOMP2
CPC1
Quad
Bias
Voltage
Regulator
Sync
Supply
CPC2
VSYNC
CPGND
Linear
Regulator
&
Watchdog
V
REF
VCCDRI
VCC
VDD
RESET
PPT
TXD
LIN
RXD
Driver Output
OUTx Monitor
Power Supply
I/O Monitor
LIN
Interface
GNDA
VSS
GND_LIN
Figure 2. 33789 Simplified Internal Block Diagram
33789
2
Analog Integrated Circuit Device Data
Freescale Semiconductor
PIN CONNECTIONS
PIN CONNECTIONS
BUCKGND
VBUCK_R
Transparent Top View
64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49
ASST
CS_C
CS_B
CS_A
SCRAP
PSI5_1
PSI5_2
PSI5_3
PSI5_4
GND_PSI
SO
SI
SCK
CLK
CS
SATSYNC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
BUCKCOMP1
BUCKCOMP2
BSTCOMP1
BSTCOMP2
VDD
VSS
VCC
GNDA
VCCDRI
DISARM
ARM
RESET
AOUT
RXD
TXD
A_SENSOR
IN9
IN8
IN7
IN6
IN5
IN4
IN3
IN2
OUT2_S
PPT
OUT2_D
OUT1_S
OUT1_D
LIN
Figure 3. 33789 Pin Connections
Table 1. 33789 Pin Definitions
A functional description of each pin can be found in the Functional Pin Description section beginning on
page 25.
Pin
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Pin Name
ASST
CS_C
CS_B
CS_A
SCRAP
PSI5_1
PSI5_2
PSI5_3
PSI5_4
GND_PSI
SO
SI
SCK
CLK
Pin
Function
Input
Input
Input
Input
Input
Input/Output
Input/Output
Input/Output
Input/Output
Ground
Output
Input
Input
Input
Formal Name
Analog Sensor Self-test
Chip Select C
Chip Select B
Chip Select A
Scrap
PSI5 Interface 1
PSI5 Interface 2
PSI5 Interface 3
PSI5 Interface 4
PSI Ground
SPI Data Out
SPI Data In
SPI Clock
Satellite Sensor Clock
Definition
Active high input to initiate analog sensor self-test
Active low SPI monitor chip select input dedicated for on-board sensor C.
Active low SPI monitor chip select input dedicated for on-board sensor B
Active low SPI monitor chip select input dedicated for on-board sensor A
Scrap command input
PSI5 standard interface 1 as satellite sensor channel 1
PSI5 standard interface 2 as satellite sensor channel 2
PSI5 standard interface 3 as satellite sensor channel 3
PSI5 standard interface 4 as satellite sensor channel 4
Dedicated ground point for PSI5 sensor
SPI data output
SPI data input
SPI clock input
Clock input for the PSI5 sensor interface(s) running in synchronous
operation mode
GND_LIN
IN1
VERDIAG
BUCKSW
BSTGND
CPGND
BSTSW
VSYNC
VBUCK
ERSW
VPWR
WAKE
CPC1
CPC2
VBST
VER
33789
Analog Integrated Circuit Device Data
Freescale Semiconductor
3
PIN CONNECTIONS
Table 1. 33789 Pin Definitions (continued)
A functional description of each pin can be found in the Functional Pin Description section beginning on
page 25.
Pin
Number
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Pin Name
CS
SATSYNC
OUT2_D
OUT2_S
PPT
OUT1_S
OUT1_D
LIN
GND_LIN
IN9
IN8
IN7
IN6
IN5
IN4
IN3
IN2
IN1
A_SENSOR
TXD
RXD
AOUT
RESET
ARM
DISARM
VCCDRI
GNDA
VCC
VSS
VDD
BSTCOMP2
BSTCOMP1
Pin
Function
Input
Input
Output
Output
Input
Output
Output
Input/output
Ground
Input
Input
Input
Input
Input
Input
Input
Input
Input
Input
Input
Output
Output
Output
Output
Output
Output
Ground
Input
Ground
Output
Input
Input
Formal Name
SPI Chip Select
Satellite Sync-pulse
Trigger
Output Driver2 Drain
Output Driver2 Source
Production Programming
and Testing
Output Driver1 Source
Output Driver1 Drain
LIN Interface
LIN Ground
Input Monitor Port 9
Input Monitor Port 8
Input Monitor Port 7
Input Monitor Port 6
Input Monitor Port 5
Input Monitor Port 4
Input Monitor Port 3
Input Monitor Port 2
Input Monitor Port 1
Analog Sensor Input
Data Input from UART
Data Output to UART
Analog Output
Reset
Arm Enable
Arm Disable
V
CC
Bypass Transistor
Drive
Analog Ground
V
CC
Input
Digital Ground
Digital Power Supply
Output
Definition
Active low SPI chip select input from MCU, also used for satellite channels
on SPI monitor
Satsync command input from MCU to trigger PSI5 Sync-pulse
Drain pin of the configurable driver2 outputs
Source pin of the configurable driver2 outputs
Active high input to enable test-mode for production programming and
testing. Not for application
Source pin of the configurable driver1 outputs
Drain pin of the configurable driver1 outputs
LIN interface. It can be configured as a bi-directional pin which represents
the single-wire bus transmitter and receiver
Dedicated ground point for a bi-directional pin which represents the single-
wire bus transmitter and receiver
Port 9 of input monitor for DC sensor
Port 8 of input monitor for DC sensor
Port 7 of input monitor for DC sensor
Port 6 of input monitor for DC sensor
Port 5 of input monitor for DC sensor
Port 4 of input monitor for DC sensor
Port 3 of input monitor for DC sensor
Port 2 of input monitor for DC sensor
Port 1 of input monitor for DC sensor
Analog sensor input for safing
Logic-level data input from MCU UART transmitter for LIN/K-line
Logic-level data output to MCU UART receiver for LIN/K-line
Analog output to send MCU scaled, multiplexed and buffered analog
signals for diagnosis
Active low reset output
Active high safing enable signal to squib driver
Active low safing enable signal to squib driver
Linear regulator drive output to control an external PNP transistor for 5.0 V
V
CC
output
Analog ground
5.0 V V
CC
input for monitoring and internal supply
Digital ground
2.5 V linear regulator output for output capacitor connection.
Boost Compensation pin2 Connection 2 to the boost converter compensation network
Boost Compensation pin1 Connection 1 to the boost converter compensation network
33789
4
Analog Integrated Circuit Device Data
Freescale Semiconductor
PIN CONNECTIONS
Table 1. 33789 Pin Definitions (continued)
A functional description of each pin can be found in the Functional Pin Description section beginning on
page 25.
Pin
Number
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
Pin Name
BUCKCOM
P2
BUCKCOM
P1
VERDIAG
BUCKGND
BUCKSW
VBST
ERSW
BSTGND
BSTSW
VER
WAKE
VPWR
VSYNC
CPC2
CPC1
CPGND
VBUCK_R
VBUCK
Pin
Function
Input
Input
Input
Ground
Output
Input
Output
Ground
Output
Input
Input
Input
Input/output
Output
Output
Ground
Input
Input
Formal Name
Buck Compensation pin2
Buck Compensation pin1
Energy Reserve
Diagnosis
Buck Converter Ground
Buck Switch
Boost Voltage Input
Energy Reserve Switch
Boost Converter Ground
Boost Switch
Energy Reserve Voltage
Wake-up
Power Supply
Sensor Sync Power
Supply
Charge Pump Capacitor
Pin2
Charge Pump Capacitor
Pin1
Charge Pump Ground
Buck Converter
Redundant Input
Buck Converter Input
Definition
Connection 2 to the buck converter compensation network
Connection 1 to the buck converter compensation network
AC coupled energy reserve diagnostic input
Ground return of the buck converter, buck switch ground
Buck switch driver output to connect buck inductor
Boost voltage input for boost loop feedback and source of buck converter,
same voltage as boost output
Storage driver output to control the energy reserve capacitor charging
Ground return of the boost converter, buck switch ground
Boost switch driver output to connect boost inductor
Energy reserve voltage input for the storage capacitor charge control and
energy reserve monitor
Wake-up signal input to start-up boost and buck converters
Battery voltage power supply input
Satellite sensor sync voltage supply charge/discharge connection
Charge pump capacitor pin2
Charge pump capacitor pin1
Charge pump ground
Redundant buck converter input to supply current for charge pump
Buck converter input for buck loop feedback and current source of charge
pump
33789
Analog Integrated Circuit Device Data
Freescale Semiconductor
5
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