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Copyright © 2013 Synaptics Incorporated. All Rights Reserved. This information and any related goods and services are provided “as is.” Synaptics makes no representations or warranties, expressed or implied. Synaptics providing you information, goods or services does not, by itself, create any express or implied license under any patent, trade mark, trade secret, copyright, mask work right, or any other intellectual property right.

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Noise Coupling

Suresh Maddineni

7th June 2015

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The DIE:

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The Unwanted Loop:

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What is Inductance?:

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What is Loop Inductance?:

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Reducing Loop Inductance:

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Reducing Loop Inductance:

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Reducing Loop Inductance:

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Reducing Loop Inductance:

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Reducing Loop Inductance:

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What is left:

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Various currents

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De-caps

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De-caps are not ideal

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Several De-caps of different values

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RF channel:

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What makes sense:

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Anatomy of a smartphone:

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What is dBm?

Consider an amplifier with equal i/p and o/p impedances , Ro:

= = Av (dB)

In RF systems, the i/p and o/p impedances are unequal. Hence the absolute signal levels are expressed in dBm.

Examples: 0dBm = 1mW , i.e, a sinusoid with Vpp = 632mV in 50ohm resistor.Thus, -100 dBm is 6.32 uV peak-peak.

A GSM TX must deliver atleast 2W ( +33dBm) in the 900Mhz band. Depending on the distance from the base station, this power must be adjustable insteps of +5dBm.

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TREX:

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ESD GSM Filter Structure: AFE2410

Same as T1329B0 Different trex_hv layout from T1329B0- designed to improve

performance at lower alphas

hv_swt pad42Ω

6pF

6pF

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Test Bench: Abs multi-block tb

Input an 800MHz RF signal after some simulation time and measure the shift in the charge integrator output

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TREX:

The GSM noise source is represented by variable amplitude Psin source of 800MHz with 50 ohms source impendence, 75 ohms termination, and 10pf coupling capacitor to the receiver TREX

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Theory: Useful Formulae

----------------------------------,1----------------------------, 2

From 1, ------------------- , then

Also, ----------------------------------------------, 3

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Theory: Diagram

After GSMfilter

pad

42Ω6pF

6pF 75Ω

800MHz RF source3nH 10pF

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Theory: Voltage at the Pad

For the case @ power of 20dBm, with an RF signal (sine wave) of 800MHz: C = 10pF, L = 3nH, R = 75 Ohms

| = 34, then,

Thus, the

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Theory: Voltage after GSM filter

After resistor and capacitor network, = 54(1 – (54/75) = 1.134VThus, the voltage after the GSM filter should be approximately 1.134V

After GSMfilter

pad

42Ω6pF

6pF

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t1326 Transcap Mode Multi-block Test bench(w/Local CBC)

w/o GSM Noise

Rterm = 75ohms, Rsrc = 50ohms, Prf=20dbmFrf=800Mhz, Ccc=10pf

zero_cbc_gain 1ct_rcvr_multiplier 17(=4.25pf)cbc_global_out_sw 1static_cbc_global_res_adj 0static_cbc_global_bias_boost 0static_cbc_global_cap_sel 4td 10nRfb 0R 0Cfb0 0Cfb1 1.15*19.092pinp_swt_res 100Ccbc 1*8pabs_en 1cbc_abs_timing_mode 1cbc_hv_en 1cbc_pad_en 0R_routing 218C_routing 0CbRx 1.5palpha 0cfb1_val 0cfb_val 7cbc_cap 5(=3.0pf)cp_en 1supply 3ibais 1ut_clk 33.33nrstrch_cyc 0rst_cyc 6strch_cyc 0integ_cyc 60NTx 18NRx 32Ct 1pCbTx 1.5pCb1 5pCb2 2pRRx 50/2RTx 20/2ds_cyc 5RESET_DUR 10reset_cyc 10vin_lo_pull_up 1.65vin_hi_pull_dn 1.65

Test

be

nch

V

aria

ble

Set

tin

gs

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Ci_out w/o GSM Noise Ci_out with GSM noise

Ci_out_neg = 1.2405V

Ci_out_pos = 1.737V

Ci_out_pos = 1.7403V

Ci_out_neg = 1.247V

w/o GSM with 20dbm GSM Delta(mV)Ci_out pos 1.7403 V 1.737 2.8Ci_out neg 1.2405 V 1.247 -6.5

t1326 Transcap Mode GSM Sims(20dbm, Ct=4.25pf, Cbc=3pf)

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t1326 Transcap Mode GSM Sims(20dbm, Ct=1pf, Cbc=1pf)

Ci_out w/o GSM Noise Ci_out with GSM noise

Ci_out_pos = 1.490V

Ci_out_pos = 1.486V

Ci_out_neg = 1.489V

Ci_out_neg = 1.487V

w/o GSM with 20dbm GSM Delta(mV)Ci_out pos 1.490 V 1.486 4.0Ci_out neg 1.489 V 1.487 3.0

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Thank You !!