Automotive camera modules

There are two possible cases for automotive camera modules: directly connected to 12V battery, or supplied by a primary power supply output of roughly 8V.
Examples of solutions suitable for automotive camera modules, whose miniaturization is continuing to advance, are presented.

Block Diagram Power Supply Requirements Recommended Products Features
Step-down
For Primary: 12V direct from battery to Secondary or DC 8V to unit internal

Specifications
VIN: ~36V or 8V
VOUT: 5V
IOUT: 500mA
fosc > 2MHz

Other points

  • Compact size / high heat dissipation / low noise
  • Even if VIN falls below VOUT due to situations such as a cold crank, VOUT is maintained as high as possible
For Primary: 12V direct from battery
XDL605 / XDL606
(XD9267 / XD9268)

Inductor built-in step-down DC/DC, PWM (XDL605), PWM/PFM (XDL606)

  • Integration of IC and coil achieves high space-saving capabilities, high efficiency, high heat dissipation, and low EMI
  • Pch SW supports 100% duty ratio to correspond VIN decrease
  • XD9267 (PWM) and XD9268 (PWM/PFM) with external coil are also available

AEC-Q100 Grade-2
VIN: 3~36V (Absolute maximum rating of 40V, and 46V < 400ms)
VOUT: 1.8V~5V (Set using external resistance. XD9267 / XD9268: 1~25V)
IOUT: 600mA
fosc: 2.2MHz
Maximum Duty ratio: 100% (Pch SW)
Soft-start: Can be externally adjusted
Power Good
Package compatible with wettable flanks (XDL605 / XDL606)
For DC 8V
XDL603 / XDL604
(XD9263 / XD9264)

Inductor built-in step-down DC/DC, PWM (XDL603), PWM/PFM (XDL604)

  • Integration of IC and coil achieves high space-saving capabilities, high efficiency, high heat dissipation, and low EMI
  • Pch SW supports 100% duty ratio to correspond VIN decrease
  • XD9263 (PWM)、XD9264 (PWM/PFM) with external coil are also available

AEC-Q100 Grade-2
VIN: 3~18V (Absolute maximum rating of 20V)
VOUT: 1.8V~5V (Set using external resistance. XD9263 / XD9264: 1~15V)
IOUT: 500mA
fosc: 2.2MHz
Maximum Duty ratio: 100% (Pch SW)
Soft-start: Can be externally adjusted
Power Good
Package compatible with wettable flanks (XDL603 / XDL604)

Step-down
For ISPs and CMOS sensors

Specifications
VOUT: 0.9V, 1.2V, 1.8V
IOUT: ~300mA
fosc > 2MHz

Other points

  • High-speed transient response, high stability
  • High efficiency
  • Low noise
XDL601 / XDL602
(XD9260 / XD9261)

Inductor built-in HiSAT-COT step-down DC/DC, PWM (XDL601), PWM/PFM (XDL602)

  • Ideal for high sensitivity sensor by low ripple and coil integration
  • High-speed transient response with HiSAT-COT control
  • XD9260 (PWM) and XD9261 (PWM/PFM) with external coil are also available

AEC-Q100 Grade-2
VIN: 2.5~5.5V
VOUT: 0.8V~3.3V (XD9260 / XD9261: 0.8~3.6V)
IOUT: 1.5A
fosc: 3.0MHz (XD9260 / XD9261: 1.2MHz, 3.0MMHz)
Package compatible with wettable flanks ( XDL601 / XDL602)

RESET
For monitoring 12V lines directly from battery

Specifications
Detect voltage: 6~7V
Release voltage: 9V

Other points

  • Hysteresis width can be set as desired
  • Release/detect delay
  • Can support positive/negative surge voltage in 12V rail
XD6132

Separated sense (VSEN) pin and capacitor delay type low-power voltage detector

  • Separated sense pin uses split resistors, making it ideal for monitoring 12V rail directly from battery
  • Sense pin include internal surge voltage protection circuit
  • Can support release / detect delays using one external capacitor
  • Detect / release delay time ratios can be selected from 4 patterns
  • Hysteresis external adjustment function makes it possible to set any desired detection / release voltages for stable operation of device

AEC-Q100 Grade-1
VIN: 1.6~6.0V
Detection voltage: 1.0V (Separated sense pin. Can be set as desired with external divider resistors)
Iq: 1.28μA

RESET with watchdog
For monitoring ISP power supply voltage and operation

Specifications
Detect voltage 1.6V
Adjustment of WDT time in accordance with ISP

XD6130 / XD6131

Voltage detector with watchdog function

  • Watchdog timeout time and release delay time can be set using one external capacitor, Cd
  • Lineup consists of XD6130 with manual reset function, and XD6131 with watchdog ON/OFF function

AEC-Q100 Grade-1
VIN: 1.5~6.0V
Detect voltage: 1.6~4.6V

Solution Overview

A large number of camera modules are now used in automobiles, with requirements for their power supplies to have even smaller sizes, higher efficiency, lower noise, and lower power consumption.

Primary step-down DC/DC

These generally have a structure where the voltage is decreased to the common voltage at the first stage, and then decreased further at the second stage to the individual required voltages to be supplied. These are referred to as the primary power supply and secondary power supply respectively.
For primary DC/DC, use a switching frequency of 2MHz or greater in consideration for EMI.
If a light load condition will be experienced for a long time, and a decrease in frequency during that time is allowed, select the PWM/PFM automatic switching type. If it is desired to keep the operating frequency constant regardless of the load condition, select the PWM fixed type.

Also, starting from conditions such as cold cranks or idling stops, or elements such as long harnesses, will cause the power supply line voltage to decrease significantly, so the Pch SW type, which supports a duty ratio of 100% and can easily maintain the output voltage even when there is a drop in input voltage, is suitable in such cases.

Step-down DC/DCs, 36V operation(Absolute maximum rating of 40V, and 46V ≦ 400ms)
XDL605: Inductor built-in PWM
XDL606: Inductor built-in PWM/PFM
XD9267: PWM
XD9268: PWM/PFM
Step-down DC/DCs, 18V operation(Absolute maximum rating of 20V)
XDL603: Inductor built-in PWM
XDL604: Inductor built-in PWM/PFM
XD9263: PWM
XD9264: PWM/PFM

Use the PG (Power Good) pin and soft-start time settings of the primary DC/DC for the rise-up sequence. After sufficient rise-up of the primary DC/DC, the CE is driven by the PG pin to perform rise-up of the secondary DC/DC, to prevent malfunctions of the ECU.

Also, in order to suppress spike noise from the primary input or radiation noise from the connected harness, it is common to use surge clamps or EMI filters at the primary DC/DC input. For information on the filter which is compatible with CISPR 25 of XDL605, refer to the noise data at the following link.

※CISPR25_Class5 Noise Data
XDL605-CISPR25_Class5.pdf[2.6MB]

Step-down DC/DC for ISP and CMOS sensor

DC/DCs with compact sizes, high-speed response, and low noise are recommended for each secondary power supply rail.

Step-down DC/DCs
XDL601: Integrated coil type PWM, high-speed transient response, low EMI
XDL602: Integrated coil type PWM/PFM, high-speed transient response, low EMI
XD9260: PWM, High-speed transient response
XD9261: PWM/PFM, High-speed transient response

Although it is common to use a value of 2MHz or greater for the DC/DC switching frequency, since it is not directly connected to the exterior using a harness as with a primary DC/DC, a relatively lower frequency may be used in some cases for greater efficiency. The XD9260 and XD9261 include both 3.0MHz and 1.2MHz types for this reason.

Also, if the rise-up / rise-down sequences for each voltage rail are specified, set them in the CE of each DC/DC with delays which use CR.

RESET IC for input voltage monitoring

Voltage detector with a separated sense (VSEN) pin is used for monitoring the input voltage on the primary side.
Monitoring the input Voltage to helps to ensure stable operation and is useful for power sequencing (when implementing start-up and shut-down sequences).

The VSEN pin uses divider resistors which are connected to the primary side input Voltage supply. The divider circuit allows the Voltage Detector to monitor voltages that exceed the absolute maximum voltage range of the IC. The VIN supply for the Voltage Detector is connected to the output side of the primary DC/DC (5.0V in our example circuit).

Voltage detector
XD6132: sense isolation, HYS (hysteresis) external adjustment, External Cd for release / detect delays, Sense pin surge voltage protection circuit

The operation indicated in the above diagram together with this voltage detector is as shown below.
Example: Case where primary VIN: 12V directly from battery, VOUT of primary DC/DC: 5V, Detection voltage of voltage detector: 7V, release voltage: 9V

(a) During application of input voltage, during recovery after cold crank
When the 12V directly from the battery rises up and the primary DC/DC rises up so that the output voltage reaches 5V, PG becomes "H".
This causes the secondary stage CE to go "H" and the secondary DC/DC starts-up and supplies voltage to the ECU.
If the Voltage Detector input voltage exceeds the release voltage of 9V, RESETB becomes "H" and the ISP is notified that the input voltage is normal.

(b) During input Voltage drop or cut-off
If the input voltage falls below the detect voltage of 7V, RESETB becomes "L" and the ISP is notified of the voltage drop.
In response to this signal, the ISP can decide to safely stop operation before the DC/DC output voltage drops or it may need to execute back-up procedures to save important data before the power fails.

Benefits can be provided here by HYS (hysteresis) external adjustment and detect delay times.

  • HYS(hysteresis)external adjustment
    In the example, the detection/release voltage = 7V / 9V, but generally voltage detectors have a release voltage fixed at a level of roughly +5% of the detection voltage, so it is not possible to designate detection / release voltages which have consideration for cold cranks in this way. Voltage detectors with HYS (hysteresis) external adjustment function makes it possible to set any desired detection voltage and release voltage using an external resistor, which is essential for applications with direct connections to batteries due to their severe fluctuations.
  • Setting of detection delay time
    If the voltage drop is only for a very short duration it can be desirable not to stop the ISP, so to avoid false resets a Voltage Detector with the detect delay function is used.

RESET IC with watchdog function, for monitoring ISP power supply voltage and operation

One RESET IC with the watchdog function can monitor both the ISP power supply voltage and normal operation.

Voltage detectors with watchdog function
XD6130: Voltage detector with watchdog function, watchdog timeout time using one external capacitor, with manual reset function
XD6131: Voltage detector with watchdog function, watchdog timeout time using one external capacitor, with watchdog ON/OFF function

The voltage monitoring function signals when the secondary DC/DC output voltage has risen up sufficiently, begins operation of the ISP, and also signals when the voltage drops to prevent malfunction of the ISP.
After ISP start-up, if a pulse from the ISP reaches the WD pin at regular interval, the operation is judged to be normal. If that signal is not received, the ISP is judged to be out of control, and it is restarted by applying a RESET signal.

As we have seen, small, compact DC/DCs and Voltage Detectors can be used to a configure a simple power supply, optimised for safe, efficient operation. Conventionally, LDOs have been used to prevent noise, but due to an increase in the quiescent current of ISP and CMOS sensor, and issues of heat associated with their miniaturization, high-performance DC/DCs are becoming required.
Furthermore, by controlling with a voltage detector with special functions as described above, it is possible to realize more suitable control for the safe and accurate operation required for Automotive equipments.

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