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OBSOLETE:
LTC1340
Low Noise, Voltage-Boosted
Varactor Driver
DESCRIPTION
The LTC
®
1340 is a varactor diode driver designed to generate
5V varactor drive from a single 3V or higher voltage supply.
It includes a low noise amplifier with an internal gain of 2.3
and a self-contained charge pump to generate output volt-
ages above the input supply. The amplifier input stage
includes a built-in offset voltage that allows the output voltage
to swing to ground without requiring OV on the input. This
feature maintains the phase detector within its linear range of
operation. The LTC1340 requires only three external surface
mount capacitors to implement a complete varactor driver
module.
The LTC1340 features output referred noise of 15µV
RMS
,
minimizing frequency deviation in PLL frequency synthe-
sizer systems. Supply current is 400µA typically with a 3V
supply, and drops to 1µA in shutdown, maximizing operating
life in battery-powered systems. Amplifier bandwidth is user-
adjustable from 10kHz up to 500kHz and the output typically
sinks or sources 20µA, allowing fast output signal changes
with a typical varactor load. The amplifier input features rail-
to-rail input common mode range, allowing it
to interface with the output of virtually any phase detector
circuit.
The LTC1340 is available in MS8 and SO-8 packages.
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Generates 5V Varactor Drive from a 3V Supply
Wide Supply Voltage Range: 2.7V to 6V
Requires Only Three External Components
Micropower Operation: 400µA at 3V Supply
Shutdown Mode Drops Supply Current Below 1µA
Low Output Noise: 15
µ
V
RMS
Amplifier Gain: 2.3
Up to 500kHz Signal Bandwidth
MS8 and SO-8 Packages
Very Low Input Bias Current: 10nA Max
Amplifier Offset Maintains Phase Detector
in Linear Region
APPLICATIONS
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5V Varactor Drive from a Single Li-Ion Cell
5V Varactor Drive from Three NiCd/NiMH Cells
Cellular Telephones
Portable RF Equipment
Radio Modems
Wireless Data Transmission
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
Low Voltage Frequency Synthesizer
3V
Spectral Plot of VCO Output Driven by LTC1340
Resolution Bandwidth = 300Hz
0dB
V
CC
= 3V
C
OUT
= 270pF
0.1µF
2
V
CC
5 IN
LOOP
FILTER
1
CP
LTC1340
8
AV
CC
0.1µF
VCO
PHASE
DETECTOR
OUT 7 0V TO 5V
A
V
= 2.3
270pF
SHDN PGND AGND
4
3
6
1340 TA01
RELATIVE POWER (10dB/DIV)
SHUTDOWN
U
FEATURES
U
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900MHz
FREQUENCY (120kHz/DIV)
1340 TA02
1
LTC1340
ABSOLUTE
MAXIMUM
RATINGS
Supply Voltage (V
CC
) ................................................. 7V
Input Voltage (AV
CC
) ............................................... 14V
Input Voltage (SHDN, IN) ............... – 0.3V to V
CC
+ 0.3V
Output Voltage (CP, OUT) ............ – 0.3V to AV
CC
+ 0.3V
Output Short-Circuit Duration .......................... Indefinite
Commercial Temperature Range ................. 0°C to 70°C
Extended Commercial Operating
Temperature Range (Note 1) ............. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec.)................. 300°C
PACKAGE/ORDER INFORMATION
TOP VIEW
CP
V
CC
SHDN
PGND
1
2
3
4
8
7
6
5
AV
CC
OUT
AGND
IN
ORDER PART
NUMBER
LTC1340CMS8
MS8 PART MARKING
LTBM
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 200°C/ W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
T
A
= 25°C, unless otherwise noted. (Note 1)
SYMBOL PARAMETER
V
CC
I
CC
V
OL
V
OH
Input Supply Voltage
Supply Current
Low Output Voltage Swing
High Output Voltage Swing
I
OUT
= 0, 2.7V
≤
V
CC
≤
6V
Shutdown, 2.7V
≤
V
CC
≤
6V
V
CC
= 2.7V, 6V,
I
OUT
= 0µA
V
CC
= 2.7V, 6V,
I
OUT
= 14µA
V
CC
= 2.7V,
I
OUT
= 0µA
V
CC
= 6V,
I
OUT
= 0µA
V
CC
= 2.7V,
I
OUT
= 14µA
V
CC
= 6V,
I
OUT
= 14µA
0.6V
≤
V
OUT
≤
4.25V, V
CC
= 2.7V
0.6V
≤
V
OUT
≤
9.75V, V
CC
= 6V
C
OUT
= 1nF,
∆V
OUT
=
±4V
0.1V
≤
V
IN
≤
V
CC
q
q
CONDITIONS
q
q
q
q
q
q
q
q
q
q
q
q
q
I
OUT
t
OUT
V
IN
I
B
V
OS
A
V
g
m
R
OUT
e
n
BW
PSRR
I
SHDN
Output Sink/Source Current
Output Transition Time
Input Voltage Range
Input Bias Current
Input Offset Voltage
Amplifier Gain
Amplifier Transconductance
Output Impedance
Output Noise Voltage
– 3dB Signal Bandwidth
Power Supply Rejection Ratio
Shutdown Logic Input Current
V
IN
= 1V, AV
CC
= 5V
V
OUT
= 2.5V, AV
CC
= 5V
V
OUT
= 2.5V, AV
CC
= 5V
V
OUT
= 1/2AV
CC
1kHz to 100kHz, C
OUT
= 1nF
C
OUT
= 1nF
AV
CC
= 4V to 6V, C
OUT
= 1nF
0.1V
≤
V
SHDN
≤
V
CC
2
U
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W
W W
U
W
TOP VIEW
CP 1
V
CC
2
SHDN 3
PGND 4
8 AV
CC
7 OUT
6 AGND
5 IN
ORDER PART
NUMBER
LTC1340CS8
S8 PART MARKING
1340
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 130°C/ W
MIN
2.7
TYP
500
1
MAX
6
900
10
0.25
0.6
UNITS
V
µA
µA
V
V
V
V
V
V
4.6
10.5
4.25
9.75
±14
±14
0
±0.01
0.15
2.1
1200
800
0.35
2.3
1800
1
15
125
25
±20
±20
200
±35
±35
285
V
CC
±1
±10
0.60
2.5
2300
3200
µA
µA
µs
V
nA
nA
V
V/V
µmho
µmho
MΩ
µV
RMS
kHz
dB
q
q
q
60
90
±0.01
±1
µA
LTC1340
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
t
START
V
RIPPLE
f
CP
Charge Pump Start-Up Time
Charge Pump Output Ripple at C
P
Charge Pump Frequency
T
A
= 25°C, unless otherwise noted. (Note 1)
MIN
q
CONDITIONS
C
CP
= 0.1µF, V
CC
= 2.7V, I
OUT
= 0
C
CP
= C
VCC
= 0.1µF, V
CC
= 2.7V, I
OUT
= 0 (Note 2)
(Note 3)
q
TYP
1.2
200
MAX
5
UNITS
ms
µV
P-P
MHz
2.5
4
The
q
denotes specifications which apply over the specified temperature
range.
Note 1:
C grade device specifications are guaranteed over the 0°C to 70°C
temperature range. In addition, C grade device specifications are assured
over the – 40°C to 85°C temperature range by design or correlation, but
are not production tested.
Note 2:
The charge pump output ripple is not tested but is correlated with
a PCB ground plane and high quality, low ESR, low ESL metalized
polyester 0.1µF capacitors.
Note 3:
The internal oscillator typically runs at 2MHz, but the charge pump
refreshes the output on both phases of the clock, resulting in an effective
4MHz operating frequency.
TYPICAL PERFORMANCE CHARACTERISTICS
DC Transfer Curve
12
11
10
OUTPUT VOLTAGE (V)
INPUT OFFSET VOLTAGE (V)
9
8
7
6
5
4
3
2
1
0
0
VOLTAGE GAIN (dB)
T
A
= 25°C
C
OUT
= 1nF
I
OUT
= 0
V
SHDN
= V
CC
1
2
3
4
INPUT VOLTAGE (V)
Output High Voltage vs
Temperature
9.4
9.3
OUTPUT HIGH VOLTAGE (V)
9.2
9.1
9.0
8.9
4.9
4.8
4.7
4.6
4.5
4.4
–50
–25
25
50
75
0
TEMPERATURE (°C)
100
125
I
OH
= 14µA, V
CC
= 2.7V
C
OUT
= 1nF
V
IN
= V
SHDN
= V
CC
I
OH
= 0, V
CC
= 2.7V
I
OH
= 14µA, V
CC
= 5V
I
OH
= 0, V
CC
= 5V
OUTPUT LOW VOLTAGE (V)
0.4
TRANSCONDUCTANCE (µmho)
U W
V
CC
= 6V
V
CC
= 5V
V
CC
= 2.7V
5
6
1340 G01
1340 G04
Gain and Phase Shift vs
Frequency
20
10
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
1
10
100
FREQUENCY (kHz)
V
CC
= 2.7V
T
A
= 25°C
C
OUT
= 1nF
PHASE
GAIN
180
144
108
72
36
0
–36
–72
–108
–144
–180
–216
1000
1340 G02
Input Offset Voltage vs
Temperature
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
–50
–25
25
50
75
0
TEMPERATURE (°C)
100
125
V
CC
= 2.7V TO 6V
C
OUT
= 1nF
V
SHDN
= V
CC
PHASE SHIFT (DEG)
1340 G03
Output Low Voltage vs
Temperature
0.5
V
CC
= 2.7V OR 5V
C
OUT
= 1nF
V
IN
= 0V
V
SHDN
= V
CC
I
OL
= 14µA
Transconductance vs
Supply Voltage
2100
2050
2000
1950
1900
1850
1800
T
A
= 25°C
V
OUT
= 1/2AV
CC
V
SHDN
= V
CC
0.3
0.2
I
OL
= 0
0.1
0
–50
–25
25
50
75
0
TEMPERATURE (°C)
100
125
2.5 3.0
3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
6.0
6.5
1340 G05
1340 G06
3
LTC1340
TYPICAL PERFORMANCE CHARACTERISTICS
Transconductance vs
Temperature
3000
2800
TRANSCONDUCTANCE (µmho)
V
OUT
= 1/2AV
CC
V
SHDN
= V
CC
2600
2400
2200
2000
1800
1600
1400
1200
1000
–50
–25
SUPPLY CURRENT (µA)
700
600
500
400
300
200
SUPPLY CURRENT (µA)
V
CC
= 6V
V
CC
= 5V
V
CC
= 2.7V
25
50
75
0
TEMPERATURE (°C)
GSM 900 MS Spectrum Due to
Modulation
10
OUTPUT VOLTAGE NOISE (µV/
RMS
)
0
–10
INPUT BIAS CURRENT (pA)
RELATIVE POWER (dB)
–20
–30
–40
–50
–60
–66
–70
–80
–90
0
MEASUREMENT
BANDWIDTH
30kHz
MEASUREMENT
BANDWIDTH
100kHz
DATA TAKEN ON
LTC DEMO BOARD DC152
LTC1340
200 400 600 1200 1800 3000 6000
FREQUENCY FROM THE CARRIER(kHz)
1340 G10
Shutdown Input Threshold vs
Temperature
2.4
SHUTDOWN INPUT THRESHOLD (V)
2.2
2.0
1.8
1.6
1.4
V
CC
= 3V
1.2
1.0
0.8
–50
V
CC
= 2.7V
0V
V
CC
= 5V
V
CC
= 4V
V
CC
= 6V
–25
25
50
75
0
TEMPERATURE (°C)
4
U W
100
1340 G07
Supply Current vs Supply Voltage
900
800
T
A
= 25°C
V
SHDN
= V
CC
700
650
600
550
500
450
400
Supply Current vs Temperature
V
SHDN
= V
CC
V
CC
= 6V
V
CC
= 5V
V
CC
= 2.7V
350
2.5 3.0
3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
6.0
6.5
300
–50
125
–25
25
50
75
0
TEMPERATURE (°C)
100
125
1340 G08
1340 G09
Output Voltage Noise vs
Temperature
25.0
22.5
20.0
17.5
15.0
12.5
10.0
7.50
5.0
1.50
0
–50
–25
25
50
75
0
TEMPERATURE (°C)
100
125
AV
CC
= 5V
C
OUT
= 1nF
1000
10000
Input Bias Current vs
Temperature
V
IN
= V
SHDN
= V
CC
= 5V
100
10
1
–50
–25
25
50
75
0
TEMPERATURE (°C)
100
125
1340 G11
1340 G12
Rail-to-Rail Step Response at
V
CC
= 6V
Rail-to-Rail Step Response at
V
CC
= 2.7V
0V
V
IN
= 0.3V TO 6V
C
OUT
= 1nF
V
IN
= 0.3V TO 2.6V
C
OUT
= 1nF
1340 G14
1340 G15
100
125
1340 G13
LTC1340
TYPICAL PERFORMANCE CHARACTERISTICS
Charge Pump Frequency vs
Temperature
4.0
V
SHDN
= V
CC
3.8
FREQUENCY (MHz)
V
CC
= 6V
V
CC
= 5V
V
CC
= 2.7V
C
OUT
= 220pF
C
OUT
= 470pF
0V
C
OUT
= 1nF
V
IN
= 0.5V TO 2V
V
CC
= 2.7V
C
OUT
= 1nF
–25
25
50
75
0
TEMPERATURE (°C)
100
125
3.6
3.4
3.2
1340 G18
3.0
–50
PIN FUNCTIONS
CP (Pin 1):
Charge Pump Output. This is the output of the
internal charge pump. The voltage at CP is nominally twice
the V
CC
input voltage. Connect CP to an external 0.1µF
filter capacitor and AV
CC
.
V
CC
(Pin 2):
Supply Input. This is the input supply to the
charge pump. V
CC
can range from 2.7V to 6V and requires
a 0.1µF bypass capacitor to PGND.
SHDN (Pin 3)
Shutdown. If SHDN is high (>V
CC
– 0.5V),
the LTC1340 operates normally. If SHDN is pulled low
(< 0.5V), the LTC1340 enters shutdown mode and the
supply current drops to less than 1µA typically. In shut-
down, the charge pump output voltage collapses and the
OUT pin enters a high impedance state. If SHDN returns
high, the charge pump output requires 1.2ms typically to
resume full voltage.
PGND (Pin 4):
Power Ground. This is the charge pump
ground. Connect PGND to the system power supply
return.
IN (Pin 5):
Signal Input. The internal amplifier amplifies
the signal input at this pin typically by 2.3 to the OUT pin.
IN accepts signals from GND to V
CC
without phase rever-
sal or unusual behavior, allowing a direct connection to the
output of virtually any phase detector or loop filter pow-
ered from V
CC
.
AGND (Pin 6):
Signal Ground. Connect AGND to the
ground plane in close proximity to the VCO ground. There
is an internal parasitic resistance of 50Ω between AGND
and PGND.
OUT (Pin 7):
Driver Output. OUT is the output of the
internal g
m
amplifier and the internal feedback network. It
swings from GND to AV
CC
, and drives a varactor load
directly. The OUT pin requires an external capacitor
(≥ 220pF) to AGND to ensure stability. OUT typically sinks
or sources 20µA.
AV
CC
(Pin 8):
Amplifier Supply. LTC recommends a direct
connection from AV
CC
to CP and also recommends a 0.1µF
filter capacitor from CP to PGND.
U W
1340 G16
Large-Signal Response
C
OUT
= 0pF
Small-Signal Response
1340 G17
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