SPRS993E March 2017 – December 2018 DRA76P , DRA77P
PRODUCTION DATA.
Refer to the PDF data sheet for device specific package drawings
Maximum acceptable PCB resistance (Reff) between the PMIC and Processor input power balls should not exceed 10 mΩ.
Maximum decoupling capacitance loop inductance (LL) between Processor input power balls and decoupling capacitances should not exceed 2.0 nH (ESL NOT included)
Impedance target for key frequency of interest between Processor input power balls and PMIC’s SMPS output power balls should not exceed 57 mΩ at 20 MHz.
Parameter | Recommendation | Example PCB |
---|---|---|
Processor OPP | High | |
Clocking Rate | 1.5 GHz | |
Voltage Level | 1.22 V | 1.22 V |
Max Current Draw | 5.12 A | 5.12 A |
Max Effective Resistance: Power Inductor Segment Total Reff | 10 mΩ | 9.0 mΩ |
Max Loop Inductance | 2.0 nH | 1.0 – 1.4 nH |
Impedance Target | 57 mΩ F < 20 MHz | 57 mΩ F < 20 MHz |
Figure 7-21, Figure 7-22, Figure 7-23, and Figure 7-24 show a PCB layout example and the resulting PI analysis results.
Net[from] | Component [from]: | Net[to] | Component [to]: | Etch Resistance (Ω) | % of Total Etch Resistance |
---|---|---|---|---|---|
SW1 | L17 | SW1 | U45 | 0,001038 | 13% |
SW2 | L15 | SW2 | U45 | 0,000898 | 12% |
SW3 | L13 | SW3 | U45 | 0,000861 | 11% |
SW1 | L17 | SMPS_1_2_3 | R181 | 0,000696 | 9% |
SW2 | L15 | SMPS_1_2_3 | R181 | 0,000541 | 7% |
SW3 | L13 | SMPS_1_2_3 | R181 | 0,000526 | 7% |
vdd_mpu | R181 | vdd_mpu | U52 | 0,006311 | 78% |
vdd_mpu | R181 | vdd_mpu | U52 | 0,006311 | 81% |
vdd_mpu | R181 | vdd_mpu | U52 | 0,006311 | 82% |
Total Etch Resistance from SW1 = | 0,008045 | 100% | |||
Total Etch Resistance from SW2 = | 0,00775 | 100% | |||
Total Etch Resistance from SW3 = | 0,007698 | 100% | |||
Max Value = | 0,008045 |
Net[from] | Component [from]: | Net[to] | Component [to]: | Etch Resistance (Ω) | % of Total Etch Resistance |
---|---|---|---|---|---|
SMPS_1_2_3 | L17 | SMPS_1_2_3 | R181 | 0,000696 | 10% |
SMPS_1_2_3 | L15 | SMPS_1_2_3 | R181 | 0,000541 | 8% |
SMPS_1_2_3 | L13 | SMPS_1_2_3 | R181 | 0,000526 | 8% |
vdd_mpu | R181 | vdd_mpu | U52 | 0,006311 | 90% |
vdd_mpu | R181 | vdd_mpu | U52 | 0,006311 | 92% |
vdd_mpu | R181 | vdd_mpu | U52 | 0,006311 | 92% |
Total Etch Resistance = | 0,007007 | 100% | |||
Total Etch Resistance = | 0,006852 | 100% | |||
Total Etch Resistance = | 0,006837 | 100% | |||
Max Value = | 0,007007 |
PDN Elements | PDN Effective Resistance (Ω) | % of Total Etch Resistance |
---|---|---|
Etch | 0,008045 | 89% |
Inductor | 0 | 0% |
Sense Resistor | 0,001 | 11% |
Max PDN Effectiv Resistance from Source | 0,009045 | 100% |
IR Drop: vdd_mpu (PCB RevJan14, Sentinel PSI)
Dynamic analysis of this PCB design for the MPU power domain determined the vdd_mpu decoupling capacitor loop inductance and impedance vs frequency analysis shown below. As you can see, the loop inductance values ranged from 1.0 to 1.4nH and were less than maximum 2.0nH recommended.
NOTE
Comparing loop inductances for capacitors at different distances from the processor’s input power balls shows an 18% reduction for caps placed closer. This was derived by averaging the inductances for the 3 caps with distances over 800mils (Avg LL = 1.33nH) vs the 3 caps with distances less than 600mils (Avg LL = 1.096nH).
Cap Ref Des | Model Port # | Loop Inductacne [nH] | Footprint Types | PCB Side | Distance to Ball-Field [mils] | Value [μF] | Size |
---|---|---|---|---|---|---|---|
C356 | 1 | 1,4 | 4vWSE | Bottom | 897 | 22 | 0603 |
C359 | 2 | 1,26 | 4vWSE | Bottom | 855 | 2,2 | 0402 |
C360 | 3 | 1,33 | 4vWSE | Bottom | 850 | 4,7 | 0402 |
C365 | 4 | 1,14 | 4vWSE | Bottom | 817 | 0,1 | 0201 |
C366 | 5 | 1,13 | 4vWSE | Bottom | 755 | 0,1 | 0201 |
C367 | 6 | 1,07 | 4vWSE | Bottom | 758 | 1 | 0201 |
C368 | 7 | 1,12 | 4vWSE | Bottom | 811 | 0,1 | 0201 |
C369 | 8 | 1,06 | 4vWSE | Bottom | 690 | 0,1 | 0201 |
C370 | 9 | 1,12 | 4vWSE | Bottom | 680 | 0,1 | 0201 |
C384 | 10 | 1,04 | 4vWSE | Bottom | 686 | 0,1 | 0201 |
C385 | 11 | 1,07 | 4vWSE | Top | 686 | 0,1 | 0201 |
C387 | 12 | 1,16 | 4vWSE | Top | 755 | 0,1 | 0201 |
C389 | 13 | 1,18 | 4vWSE | Top | 693 | 0,1 | 0201 |
C391 | 14 | 1,14 | 4vWSE | Bottom | 693 | 0,1 | 0201 |
C392 | 15 | 1,18 | 4vWSE | Bottom | 542 | 0,1 | 0201 |
C396 | 16 | 1,11 | 4vWSE | Bottom | 745 | 0,1 | 0201 |
C91 | 17 | 1,1 | 4vWSE | Bottom | 515 | 1 | 0201 |
C92 | 18 | 1,09 | 4vWSE | Bottom | 622 | 0,22 | 0201 |
C93 | 19 | 1,01 | 4vWSE | Bottom | 504 | 0,47 | 0201 |
C94 | 20 | 1,13 | 4vWSE | Bottom | 604 | 0,47 | 0201 |
C95 | 21 | 1,04 | 4vWSE | Bottom | 612 | 1 | 0201 |
C96 | 22 | 1,08 | 4vWSE | Top | 612 | 0,22 | 0201 |
Loop Inductance range: 1,01 - 1,40 nH
Figure 7-27 shows vdd_mpu Impedance vs Frequency characteristics.