參數(shù)資料
型號(hào): LMX1501
廠商: National Semiconductor Corporation
英文描述: PLLatinumTM 1.1 GHz Frequency Synthesizer for RF Personal Communications
中文描述: PLLatinumTM 1.1千兆赫頻率合成射頻個(gè)人通信
文件頁數(shù): 19/22頁
文件大?。?/td> 367K
代理商: LMX1501
Application Information
(Continued)
EXTERNAL CHARGE PUMP
The LMX PLLatimum series of frequency synthesizers are
equipped with an internal balanced charge pump as well as
outputs for driving an external charge pump. Although the
superior performance of NSC’s on board charge pump elim-
inates the need for an external charge pump in most appli-
cations, certain system requirements are more stringent. In
these cases, using an external charge pump allows the de-
signer to take direct control of such parameters as charge
pump voltage swing, current magnitude, TRI-STATE leak-
age, and temperature compensation.
One possible architecture for an external charge pump cur-
rent source is shown in Figure 9. The signals
w
p
and
w
r
in
the diagram, correspond to the phase detector outputs of
the LMX1501/1511 frequency synthesizers. These logic
signals are converted into current pulses, using the circuitry
shown in Figure 9, to enable either charging or discharging
of the loop filter components to control the output frequency
of the PLL.
Referring toFigure 9, the design goal is to generate a 5 mA
current which is relatively constant to within 5V of the power
supply rail. To accomplish this, it is important to establish as
large of a voltage drop across R5, R8 as possible without
saturating Q2, Q4. A voltage of approximately 300 mV pro-
vides a good compromise. This allows the current source
reference being generated to be relatively repeatable in the
absence of good Q1, Q2/Q3, Q4 matching. (Matched tran-
sistor pairs is recommended.) The
w
p and
w
r outputs are
rated for a maximum output load current of 1 mA while 5 mA
current sources are desired. The voltages developed across
R4, 9 will consequently be approximately 258 mV, or 42 mV
k
R8, 5, due to the current density differences
à
0.026
*
1n (5
mA/1 mA)
ó
through the Q1, Q2/Q3, Q4 pairs.
In order to calculate the value of R7 it is necessary to first
estimate the forward base to emitter voltage drop (Vfn,p) of
the transistors used, the V
OL
drop of
w
p, and the V
OH
drop
of
w
r’s under 1 mA loads. (
w
p’s V
OL
k
0.1V and
w
r;s V
OH
k
0.1V.)
Knowing these parameters along with the desired current
allow us to design a simple external charge pump. Separat-
ing the pump up and pump down circuits facilitates the no-
dal analysis and give the following equations.
R
4
e
V
R5
b
V
T
#
1n
i
source
i
p max
i
source
R
9
e
V
R8
b
V
T
#
1n
i
sink
i
n max
i
sink
R
5
e
V
R5
#
(
b
p
a
1)
i
p max
#
(
b
p
a
1)
b
i
source
V
R8
#
(
b
n
a
1)
i
r max
#
(
b
n
a
1)
b
i
sink
R
6
e
(V
p
b
V
VOL
w
p
)
b
(V
R5
a
Vfp)
R
8
e
i
p max
R
7
e
(V
P
b
V
VOH
w
r
)
b
(V
R8
a
Vfn)
i
max
EXAMPLE
Typical Device Parameters
b
n
e
100,
b
p
e
50
V
P
e
5.0V;
V
cntl
e
0.5V
b
4.5V;
V
w
p
e
0.0V, V
w
r
e
5.0V
I
SINK
e
I
SOURCE
e
5.0 mA;
V
fn
e
V
fp
e
0.8V
I
rmax
e
I
pmax
e
1 mA
V
R8
e
V
R5
e
0.3V
V
OL
w
p
e
V
OH
w
r
e
100 mV
Typical System Parameters
Design Parameters
TL/W/12340–46
FIGURE 9
Therefore select
R
4
e
R
9
e
0.3V
b
0.026
#
1n(5.0 mA/1.0 mA)
5 mA
e
51.6
X
R
5
e
0.3V
#
(50
a
1)
1.0 mA
#
(50
a
1)
b
5.0 mA
0.3V
#
(100
b
1)
1.0 mA
#
(100
a
1)
b
5.0 mA
R
6
e
R
7
e
(5V
b
0.1V)
b
(0.3V
a
0.8V)
e
332
X
R
8
e
e
315.6
X
1.0 mA
e
3.8 k
X
19
相關(guān)PDF資料
PDF描述
LMX1501AM PLLatinumTM 1.1 GHz Frequency Synthesizer for RF Personal Communications
LMX1501AMX PLLatinumTM 1.1 GHz Frequency Synthesizer for RF Personal Communications
LMX15010AM 1.1 GHz Frequency Synthesizer for RF Personal Communications(367.82 k)
LMX1600SLB PLLatinum⑩ Low Cost Dual Frequency Synthesizer
LMX1600TM PLLatinum⑩ Low Cost Dual Frequency Synthesizer
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LMX15010AM 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1.1 GHz Frequency Synthesizer for RF Personal Communications(367.82 k)
LMX1501A 制造商:NSC 制造商全稱:National Semiconductor 功能描述:PLLatinumTM 1.1 GHz Frequency Synthesizer for RF Personal Communications
LMX1501AM 制造商:NSC 制造商全稱:National Semiconductor 功能描述:PLLatinumTM 1.1 GHz Frequency Synthesizer for RF Personal Communications
LMX1501AMX 功能描述:IC FREQ SYNTHESIZR 1.1GHZ 16SOIC RoHS:否 類別:集成電路 (IC) >> 時(shí)鐘/計(jì)時(shí) - 時(shí)鐘發(fā)生器,PLL,頻率合成器 系列:PLLatinum™ 標(biāo)準(zhǔn)包裝:39 系列:- 類型:* PLL:帶旁路 輸入:時(shí)鐘 輸出:時(shí)鐘 電路數(shù):1 比率 - 輸入:輸出:1:10 差分 - 輸入:輸出:是/是 頻率 - 最大:170MHz 除法器/乘法器:無/無 電源電壓:2.375 V ~ 3.465 V 工作溫度:0°C ~ 70°C 安裝類型:* 封裝/外殼:* 供應(yīng)商設(shè)備封裝:* 包裝:*
LMX1511 制造商:NSC 制造商全稱:National Semiconductor 功能描述:PLLatinumTM 1.1 GHz Frequency Synthesizer for RF Personal Communications