ZHCSP40B October 2021 – June 2022 LMX2571-EP
PRODUCTION DATA
First of all, calculate all the frequencies in each functional block.
Assign F1 frequency to be 902 MHz. With CHDIV1 = 5 and CHDIV2 = 1, the total division is 5. As a result, the VCO frequency will be 902 × 5 = 4510 MHz, which is within the VCO tuning range.
OSCin is 26 MHz, put Pre-divider = 1 to meet the MULT input frequency range requirement.
To meet the maximum MULT output frequency requirement, possible MULT values are 3 to 5. Play around the allowable MULT values and Post-divider values to get the optimum phase noise and spurs performance. Assuming MULT = 4 and Post-divider = 1 returns the best performance, then fPD = 104 MHz.
N-divider = 21.68269231, that means Ninteger = 21 while Nfrac = 0.68269231. To use the direct digital modulation feature, put fractional denominator, DEN = 0. The actual DEN value is, in fact, equal to 224 = 16777216. So the fractional numerator, NUM, is equal to Nfrac × DEN = 11453676.
Use Equation 4 and Equation 6 to calculate the required FSK steps. For +10-kHz frequency deviation, the FSK step value is equal to [10000 × 16777216 / (104 × 106)] × (5 × 1 / 2) = 4033. For –10-kHz frequency deviation, the FSK step value is equal to 2's complement of 4033 = 61502. Similarly, the FSK step values for ±30-kHz frequency deviation are 12099 and 53436.
All the required configuration values for F2, 928 MHz can be calculated in the similar fashion and are summarized as follows:
CONFIGURATION PARAMETER | F1 (902 MHz) | F2 (928 MHz) |
---|---|---|
Pre-divider | 1 | 1 |
MULT | 4 | 4 |
Post-divider | 1 | 1 |
104 MHz | 104 MHz | |
VCO | 4510 MHz | 4640 MHz |
N-divider | 21.68269231 | 22.30769231 |
Ninteger | 21 | 22 |
DEN | 0 | 0 |
NUM | 11453676 | 5162220 |
CHDIV1 | 5 | 5 |
CHDIV2 | 1 | 1 |
FSK_DEV0 | 4033 | |
FSK_DEV1 | 12099 | |
FSK_DEV2 | 61502 | |
FSK_DEV3 | 53436 |
Assume here that the base charge pump current = 1250 µA, CP Gain = 1x and 3rd order Delta Sigma Modulator without dithering is adopted in both frequency sets. The register settings are summarized as follows:
CONFIGURATION PARAMETERS | REGISTER BIT | COMMON SETTING | F1 SPECIFIC SETTING | F2 SPECIFIC SETTING |
---|---|---|---|---|
VCO calibration | FCAL_EN | 1 = Enabled | ||
Lock detect | SDO_LE_SEL | 1 = Lock detect output | ||
LD_EN | 1 = Enabled | |||
Dithering | DITHERING | 0 = Disabled | ||
Charge pump gain | CP_GAIN | 1 = 1x | ||
Base charge pump current | CP_IUP | 8 = 1250 µA | ||
CP_IDN | 8 = 1250 µA | |||
MULT settling time | MULT_WAIT | 520 = 20 µs | ||
Output buffer type | OUTBUF_RX_TYPE | 1 = Push pull | ||
OUTBUF_TX_TYPE | 1 = Push pull | |||
Output buffer auto mute | OUTBUF_AUTOMUTE | 0 = Disabled | ||
Enable F1 F2 initialization | F1F2_MODE | 1 = Enabled | ||
Pre-divider | PLL_R_PRE_F1 | 1 | ||
PLL_R_PRE_F2 | 1 | |||
MULT multiplier | MULT_F1 | 4 | ||
MULT_F2 | 4 | |||
Post-divider | PLL_R_F1 | 1 | ||
PLL_R_F2 | 1 | |||
ΔΣ modulator order | FRAC_ORDER_F1 | 3 = 3rd order | ||
FRAC_ORDER_F2 | 3 = 3rd order | |||
PFD delay | PFD_DELAY_F1 | 5 = 8 clock cycles | ||
PFD_DELAY_F2 | 5 = 8 clock cycles | |||
CHDIV1 divider | CHDIV1_F1 | 1 = Divide by 5 | ||
CHDIV1_F2 | 1 = Divide by 5 | |||
CHDIV2 divider | CHDIV2_F1 | 0 = Divide by 1 | ||
CHDIV2_F2 | 0 = Divide by 1 | |||
Internal 3rd pole loop filter | LF_R3_F1 | 4 = 800 Ω | ||
LF_R3_F2 | 4 = 800 Ω | |||
Internal 4th pole loop filter | LF_R4_F1 | 4 = 800 Ω | ||
LF_R4_F2 | 4 = 800 Ω | |||
Output port selection | OUTBUF_TX_EN_F1 | 1 = TX port enabled | ||
OUTBUF_RX_EN_F2 | 1 = RX port enabled | |||
Output power control | OUTBUF_TX_PWR_F1 | 6 | ||
OUTBUF_RX_PWR_F2 | 6 | |||
FSK mode | FSK_MODE_SEL1 FSK_MODE_SEL0 | 00 = FSK PIN mode | ||
FSK level | FSK_LEVEL | 2 = 4FSK | ||
Enable FSK modulation | FSK_EN_F1 | 1 = Enabled | ||
FSK deviation at 00 | FSK_DEV0_F1 | 4033 = +10 kHz | ||
FSK deviation at 01 | FSK_DEV1_F1 | 12099 = +30 kHz | ||
FSK deviation at 10 | FSK_DEV2_F1 | 61502 = -10 kHz | ||
FSK deviation at 11 | FSK_DEV3_F1 | 53436 = -30 kHz | ||
Fractional denominator | PLL_DEN_F1[23:16] | 0 | ||
PLL_DEN_F1[15:0] | 0 | |||
PLL_DEN_F2[23:16] | 0 | |||
PLL_DEN_F2[15:0] | 0 | |||
Fractional numerator | PLL_NUM_F1[23:16] | 174 | ||
PLL_NUM_F1[15:0] | 50412 | |||
PLL_NUM_F2[23:16] | 78 | |||
PLL_NUM_F2[15:0] | 50412 | |||
Ninteger | PLL_N_F1 | 21 | ||
PLL_N_F2 | 22 | |||
Prescaler | PLL_N_PRE_F1 | 0 = Divide by 2 | ||
PLL_N_PRE_F2 | 0 = Divide by 2 |