[FAQ] How to drop a DRV8452 into a DRV8434S socket? Advantages?

The DRV8452 (SPI version) and DRV8434S are pin-to-pin compatible with each other, with DRV8452 offering some newer features and performance improvements at a competitive price-point.  Very few changes are required to redesign a system to use the newer, higher-power DRV8452.  This FAQ goes through items to keep in mind when upgrading from DRV8434S to DRV8452.  

Advantages of DRV8452:

• Larger Full-scale current, from 2.5A to 4A in the same package
• Advanced features:  The DRV8452 has many new features including Auto-torque, Auto-microstepping, Silent Step, Standstill power saving, Customizable Microstepping

Differences to keep in mind:

• VREF:  Due to having a larger full-scale current, the same voltage of VREF on DRV8452 will result in a larger amount of current vs the DRV8434S.  DRV8452 full-scale current (IFS) is 4A in PWP package, and DRV8434S IFS is 2.5A, so multiply the DRV8434S VREF voltage by 2.5/4 to achieve the same current regulation level. 
  • For example, if VREF = 0.80V in DRV8434S.  0.80V * 2.5 / 4 = 0.50V for same current regulation level in DRV8452. 
• External components:  Several external components require different values between each device:
  • COMPONENT	DRV8434S Recommended	DRV8452 Recommended
    CVCP	X7R, 0.22 uF, 16 V capacitor	X7R, 1 uF, 16 V capacitor
    CSW	X7R, 0.022 uF, VM-rated capacitor	X7R, 0.1 uF, VM-rated capacitor
    CDVDD	X7R, 0.47 uF to 1uF, 6.3 V capacitor	X7R, 1 uF 6.3 V ceramic capacitor

     
• Off-Time PWM Chopping:  The values of the time for Off-Time PWM chopping are slightly different between the two devices.  See table below

  • TOFF state	DRV8434S	DRV8452	UNIT
    TOFF = 00b	7	9	μs
    TOFF = 01b	16	19	μs
    TOFF = 10b	24	27	μs
    TOFF = 11b	32	35	μs

       
• Decay Mode:  Three decay modes are unavailable in DRV8452 as shown in the table below. 
  

  • DECAY bits [2:0]	DRV8434S	DRV8452
    000b	Increasing SLOW, decreasing SLOW	Slow decay
    001b	Increasing SLOW, decreasing MIXED 30%	Reserved
    010b	Increasing SLOW, decreasing MIXED 60%	Reserved
    011b	Increasing SLOW, decreasing FAST	Reserved
    100b	Increasing MIXED 30%, decreasing MIXED 30%	Mixed 30% decay
    101b	Increasing MIXED 60%, decreasing MIXED 60%	Mixed 60% decay
    110b	Smart tune Dynamic Decay	Smart tune Dynamic Decay
    111b	Smart tune Ripple Control	Smart tune Ripple Control

       
• Register Map:  Many registers have been added and some register fields have been moved or renamed. See the table below for an illustration of the changes. 
  • Register fields moved:
    • TRQ_DAC: Moved from Register Address 0x03 to 0x0E and was expanded from 4-bits to 8-bits.
    • OL_MODE:  Moved from Register Address 0x03 to 0x0C and moved bitfield from 1 to 6.
    • EN_OL: Moved from Register Address 0x06 to 0x0C and moved bitfield from 3 to 7.
  • Register fields removed:
    • REV_ID
  • Register fiends renamed:
    • EN_SSC has changed to DIS_SSC. The functionality of this bit has also flipped.  In DRV8434S, setting this bit = 1 results in Spread-Spectrum Enabled, whereas in DRV8452 this bit = 1 results in Spread-Spectrum Disabled. 
  • Note that the Register Name has changed for most registers, due to register 0x03 being renamed from "CTRL1" in DRV8434S to "DIAG3" in DRV8452.  This resulted in all the CTRL# being decremented by 1 - CTRL2 renamed to CTRL1, CTRL3 renamed to CTRL2, etc.  From a programming perspective since the Register Address didn't change this won't require any extensive firmware fixes.