SSM2604 Rout, Lout Bias Voltage

Discussion created by S_Heep on Jul 4, 2018
Latest reply on Jul 6, 2018 by S_Heep



In a product of our company that uses the SSM2604, in some circumstances which are not clear to us, one or both of the outputs Rout / Lout are biased to a voltage different from that on Vmid pin.

While Vmid is at 1,65V (Vcc / 2) one or both of the outputs sometimes are biased at 2,9V for example. Other voltage levels can also be observed.


This results in distortion and noise.


CONTROL REGISTER SEQUENCING is done in the following manner:

        Registers are written in this order with the given values.

0x34, 0x00, 0x80,     //R0  00110100  00000000 10000000 -> |0011010 0|0000000|010000000
0x34, 0x02, 0x80,     //R1  00110100  00000010 10000000 -> |0011010 0|0000001|010000000
0x34, 0x08, 0x10,     //R4  00110100  00001000 00010000 -> |0011010 0|0000100|000010000
0x34, 0x0A, 0x06,     //R5  00110100  00001010 00000110 -> |0011010 0|0000101|000000110
0x34, 0x0C, 0x17,     //R6  00110100  00001100 00010111 -> |0011010 0|0000110|000010111  // Enables Vmid! Vmid.

// C starts charging.

0x34, 0x0E, 0x0A,     //R7  00110100  00001110 00001010 -> |0011010 0|0000111|000001010


wait for 500mS


0x34, 0x12, 0x01,     //R9  00110100  00010010 00000001 -> |0011010 0|0001001|000000001 // Set active bit.


Also we are slightly confused about the control register sequencing described in the datasheet.

In the datasheet REV.A of SSM2604 on page 15 is stated that after this control sequence, the bit D4 of Register R6 also should be cleared. Unfortunately the SSM2604 has no function assigned to this bit...


This leaves room for doubts about the correctness of the mentioned register sequencing.


Please help us to identify and solve this issue.


Best regards,


Stephan Heep