Si3402-A-GM to Si3402-B-GM EVB Modifications
Version 0.4
The Si3402-B-GM device requires component value changes from those used with the Si3402-A-GM
evaluation board (EVB) reference design. Table 1 below is a summary of the required modifications.
Following Table 1 are two reference schematic excerpts showing the locations of the modified
component values for both the isolated (flyback) and non-isolated (buck) topologies.
Table 1. Si3402-B-GM EVB modifications versus the Si3402-A-GM EVB
Item Modification description
M1
Detect resistor value
change
M2
Classification resistor value
change
Application design effect
The former 25.5kΩ detect resistor must be replaced by 24.3kΩ
1%
The following 1% resistors must be used:
Class0: 681.00 or higher (It is optional to place this resistor)
Class1: 140.0
Class2: 75.0
Class3: 48.7
Class4: 33.2
M3*
ISO EVB DCDC 3.3V changes
Flyback
C8, R9 & C23 are not need—Do not populate them.
C9=10nF, C21=33nF, R12=475 Ω & R8=1.1k Ω
Replace D2 (DFLT15A) with DFLT30A
* See Revision Notes
M4
ISO EVB DCDC 5V changes
Flyback
C8, R9 & C23 are not need—Do not populate them.
C9=3.3nF, C21=15nF, R12=0 & R8=0 (place zero Ω resistors)
Replace D2 (DFLT15A) with DFLT30A
M5
ISO EVB DCDC 12V changes
Flyback
C8, R9 & C23 are not need—Do not populate them.
C9=10nF, C21=15nF, R12=0, R8=0 (place zero Ω resistor)
R7=3k
Replace D2 (DFLT15A) with DFLT30A
M6
DCDC reference voltage
change (Buck case only)
Now 1.35V instead of previous 1.23V. Thus, R5 changes from
2.87kΩ 1% to 3.24kΩ 1%. R6 (1%) is modified according to this
table:
SILICON LABS CONFIDENTIAL
Vout Target
3.3
5
9
12
M7
BUCK EVB DCDC 3.3V
compensation network
changes
R5 kΩ
3.24
3.24
3.24
3.24
R6 kΩ
4.64
8.66
18.2
25.5
Vref
1.35
1.35
1.35
1.35
Vout Measured
3.37
4.96
8.93
11.98
C19, C20 & C9 are not need—Do not populate them.
R8 can be populated with a 0Ω resistor (creating a short
between pins 3 and 4) or left unpopulated, since the ISOSSFT
function is now internal (see datasheet).
C7=1nF, R7=47kΩ ±20%.
M8
BUCK EVB DCDC 5V
compensation network
changes
C19, C20, R8 & C9 are not need—Do not populate them.
R8 can be populated with a 0Ω resistor (creating a short
between pins 3 and 4) or left unpopulated, since the ISOSSFT
function is now internal (see datasheet).
C7=1nF, R7=47kΩ ±20%.
M9
BUCK EVB DCDC 12V
compensation network
changes
C19, C20, R8 & C9 are not need—Do not populate them.
R8 can be populated with a 0Ω resistor (creating a short
between pins 3 and 4) or left unpopulated, since the ISOSSFT
function is now internal (see datasheet).
C7=1nF, R7=47kΩ ±20%.
SILICON LABS CONFIDENTIAL
Si3402ISO (Flyback, Isolated) EVB Reference Design – 5V
See M2
24.3kΩ
0Ω
DFLT30A
15nF
3.3nF
0Ω
SILICON LABS CONFIDENTIAL
Si3402 (Buck, Non-Isolated) EVB Reference Design - 5V
See M2
24.3kΩ
1nF
See M6
See M7-M9
SILICON LABS CONFIDENTIAL
47kΩ
Revision Notes
26 August 2015:
Added B5 indicating the Si3402-B-EN1 samples should be run only at room temperature
Clarified Buck (Non-Isolated) case R7 to standard value 47kΩ and relaxed to 20% tolerance
28 October 2015:
Previous version silicon errata resolved
Several components in the change list updated
Document renamed “Si3402-B
RevA3 Change List_<YYYYMMDD>”
24 November 2015:
M2 and M6 components updated
Aligns with production Si3402-B-GM silicon
08 December 2015: (Version 0.3)
Changed title of doc and name of file
Clarified M7-M9 changes with regard to R8
21 March 2016: (Version 0.4)
Updated M3, the 3.3V Isolated Flyback case.
o
Explanation: 3.3V Flyback compensation was updated to address a small overshoot
condition under no-load conditions (3.66V is allowed, the overshoot was 3.73V). The
problem is fixed with revised compensation with a resulting overshoot of about 3.5V.
o
If a no-load condition is unlikely, the customer may keep the original M3 change
recommendation:
C8, R9 & C23 are not need—Do not populate them
C9=3.3nF, C21=15nF, R12=0 & R8=0 (place zero Ω resistors)
Replace D2 (DFLT15A) with DFLT30A
SILICON LABS CONFIDENTIAL
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