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AK1541 参数 Datasheet PDF下载

AK1541图片预览
型号: AK1541
PDF下载: 下载PDF文件 查看货源
内容描述: 20〜 600MHz的Σ-Δ小数-N频率合成器 [20 to 600MHz Delta-Sigma Fractional -N Frequency Synthesizer]
分类和应用:
文件页数/大小: 36 页 / 909 K
品牌: AKM [ ASAHI KASEI MICROSYSTEMS ]
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[AK1541]  
3. Fast Lockup Mode  
Setting D[16] = {FASTEN} in <Address4> to 1enables the Fast Lock Up mode for the AK1541.  
Changing a frequency setting( The frequency is changed at the rising edge of [LE] when <Address1> and <Address2>  
are accessed.) or [PDN2] pin is set Lowto Highwith {FASTEN}=1 enables the Fast Lockup mode. The loop filter switch  
turns ON during the timer period specified by the counter value in D[12:0] = {FAST[12:0]} in <Address4>, and the charge  
pump for the Fast Lockup mode (Charge Pump 2) is enabled. After the timer period elapsed, the loop filter switch turns  
OFF. The charge pump for normal operation (Charge Pump 1) is enabled..  
D[12:0] ={ FAST[12:0]} in <Address4> is used to set the timer period for this mode.  
The following formula is used to calculate the time period:  
Phase detector frequency cycle x counter value set in {FAST[12:0]}  
The charge pump current can be changed with the register setting in 16 steps in normal operation (Charge Pump 1) and 8  
steps in the Fast Lockup operation (Charge Pump 2).  
The charge pump current for normal operation (Charge Pump 1) is determined by the setting in {CP1[3:0]}, which is a 4-bit  
address of D[18:15] in <Address2>, and a value of the resistance connected to the [BIAS] pin (19). The following formulas  
show the relationship between the resistance value, the register setting and the electric current value.  
Charge Pump 1 minimum current (CP1_min) = 0.285 / Resistance connected to the [BIAS] pin (19)  
Charge Pump 1 current = CP1_min x (Charge Pump 1 setting + 1)  
The charge pump current for the Fast Lockup mode operation (Charge Pump 2 current) is determined by the setting in  
{CP2[2:0]}, which is a 3-bit address of D[15:13] in <Address4>, and a value of the resistance connected to the BIAS pin  
The following formula show the relationship between the resistance value, the register setting and the electric current  
value.  
Charge Pump 2 minimum current (CP2_min) = 5.7 / Resistance connected to the [BIAS] pin  
Charge Pump 2 minimum current (CP2_min) = CP2_min x (Charge Pump 2 setting + 4)  
The allowed range value for the resistance (connected to the [BIAS] pin (19)) is from 33 to 22 [kΩ] for both normal and  
Fast Lockup mode operations. For details of current settings, see 10. Register Functional Description”.  
First lockup time specified  
by the timer  
Operation mode  
Charge pump  
Normal  
Charge pump 1  
OFF  
Fast Lockup Mode  
Charge pump 2  
ON  
Normal  
Charge pump 1  
OFF  
Lop filter switch  
The frequency is changed or [PDN2] pin is set ”Low” to ”High when D[16]={FSTEN}  
in < Address4 > is set to”1”.  
Fig. 6 Timing Chart for Fast Lockup Mode  
MS1043-E-05  
13  
2013/03