LINER LTC4400

LTC4400-1/LTC4400-2
RF Power Controllers with
450kHz Loop BW and
45dB Dynamic Range
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FEATURES
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DESCRIPTIO
RF Power Amplifier Control in ThinSOTTM Package
Internal Schottky Diode Detector with > 45dB Range
Wide Input Frequency Range:
300MHz to 2.7GHz (LTC4400-1)
300MHz to 2GHz (LTC4400-2)
Autozero Loop Cancels Offset Errors and
Temperature Dependent Offsets
Wide VCC Range: 2.7V to 6V
Automatic Bandwidth Control Improves Low Power
Ramp Response
Allows Direct Connection to Battery
RF Output Power Set by External DAC
Internal Frequency Compensation
Rail-to-Rail Power Control Output
Power Control Signal Overvoltage Protection
Low Operating Current: 1mA
Low Shutdown Current: 10µA
Two Pole PCTL Input Filtering
Low Profile (1mm) ThinSOT (LTC4400-1) and
8-Pin MSOP (LTC4400-2) Packages
The LTC®4400-1 is a SOT-23 RF power controller for fast
turn-on RF power amplifiers operating in the 300MHz to
2.7GHz range. Examples include the Hitachi PF08109B,
PF08122B, PF08123B, PF08107B and RF Micro Devices
RF3108. For slow turn-on RF power amplifiers refer to the
LTC4401-1/LTC4401-2.
RF power is controlled by driving the RF amplifier power
control pin and sensing the resultant RF output power via
a directional coupler or capacitive tap. The RF input
voltage is peak detected using an on-chip Schottky diode.
This detected voltage is compared to the DAC voltage at
the PCTL pin to control the output power. The RF power
amplifier is protected against high power control pin
voltages.
Internal and external offsets are cancelled over temperature by an autozero control loop, allowing accurate low
power programming. The shutdown feature disables the
part and reduces the supply current to <10µA.
A dual control channel version (LTC4400-2) is also
available in an 8-pin MSOP package.
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APPLICATIO S
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, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
GSM/GPRS Cellular Telephones
PCS Devices
Wireless Data Modems
U.S. TDMA Cellular Phones
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TYPICAL APPLICATIO
LTC4400-1 Detector Characteristics at
900MHz and 1800MHz
10000
PCTL REFERENCED DETECTOR
OUTPUT VOLTAGE (mV)
LTC4400-1 Dual Band Cellular Telephone Transmitter
50Ω
Li-Ion
0.1µF
6
VCC
RF
BAND
SELECT
1
0.4pF
LTC4400-1
SHDN
4
3
DAC
SHDN
VPCA
PCTL
GND
5
2
VPC
900MHz
INPUT
1.8GHz
INPUT
900MHz
OUTPUT
TA = 25°C
VCC = 3.6V
1000
900MHz
100
1800MHz
10
PA MODULE
1.8GHz
OUTPUT
1
–26 –22 –18 –14 –10 –6 –2 2 6 10 14 18
RF INPUT POWER (dBm)
4400 TA01
4400 TA04
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LTC4400-1/LTC4400-2
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ABSOLUTE
RATI GS
(Note 1)
VCC to GND .............................................. – 0.3V to 6.5V
VPCA/B Voltage to GND ............................ – 0.3V to 3.2V
PCTL Voltage to GND ................. – 0.3V to (VCC + 0.3V)
RF Voltage to GND ............................ (VCC – 2.6V) to 7V
BSEL, SHDN Voltage to GND ...... – 0.3V to (VCC + 0.3V)
IVPCA/B .................................................................. 10mA
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Maximum Junction Temperature ........................ 125°C
Lead Temperature (Soldering, 10 sec)................ 300°C
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PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
TOP VIEW
RF 1
6 VCC
GND 2
5 VPCA
PCTL 3
4 SHDN
LTC4400-1ES6
S6 PART MARKING
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
TJMAX = 125°C, θJA = 230°C/W
LTWZ
ORDER PART
NUMBER
TOP VIEW
VCC
VPCA
VPCB
GND
1
2
3
4
8
7
6
5
RF
BSEL
SHDN
PCTL
LTC4400-2EMS8
MS8 PACKAGE
8-LEAD PLASTIC MSOP
MS8 PART MARKING
TJMAX = 125°C, θJA = 250°C/W
LTXB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 3.6V, SHDN = HI, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
VCC Operating Voltage
●
TYP
MAX
6
V
10
20
µA
2.7
UNITS
IVCC Shutdown Current
SHDN = 0V
●
IVCC Operating Current
SHDN = HI, IVPCA/B = 0mA
●
VPCA/B VOL
RLOAD = 400Ω, Enabled
●
VPCA/B Dropout Voltage
ILOAD = 6mA, VCC = 2.7V
●
VPCA/B Voltage Clamp
PCTL = 1V
●
2.7
2.9
VPCA/B Output Current
VPCA/B = 2.4V, VCC = 3V
●
7
10
9
10.2
µs
350
450
230
560
kHz
kHz
100
pF
VPCA/B Enable Time
SHDN = VCC (Note 5)
VPCA/B Bandwidth
CLOAD = 100pF, RLOAD = 400Ω (Note 8)
VPCA/B Load Capacitance
VPCA/B Slew Rate
1.2
0
●
PCTL < 80mV
PCTL > 160mV
●
●
VPCTL = 2V Step, CLOAD = 100pF,
RLOAD = 400Ω (Note 3)
●
1.8
VPCA/B Droop
mA
V
VCC – 0.25
V
3.1
V
mA
3
V/µs
µV/ms
1
VPCA/B Start Voltage
Open Loop (Note 9)
●
270
BSEL, SHDN Input Threshold
VCC = 2.7V to 6V
●
0.35
BSEL, SHDN Input Current
BSEL = SHDN = 3.6V
●
16
PCTL Input Voltage Range
(Note 7)
●
0
●
60
PCTL Input Resistance
PCTL Input Filter
Autozero Range
2.5
1.9
0.05
450
24
90
550
mV
1.4
V
36
µA
2.4
V
120
kΩ
270
(Note 4)
●
kHz
400
mV
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LTC4400-1/LTC4400-2
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 3.6V, SHDN = HI, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
MAX
UNITS
RF Input Frequency Range
LTC4400-1(Note 6)
LTC4400-2(Note 6)
300
300
2700
2000
MHz
MHz
RF Input Power Range
(LTC4400-1)
RF Frequency = 900MHz (Note 6)
RF Frequency = 1800MHz (Note 6)
RF Frequency = 2400MHz (Note 6)
RF Frequency = 2700MHz (Note 6)
–28
–26
–24
–22
18
18
16
16
dBm
dBm
dBm
dBm
RF Input Power Range
(LTC4400-2)
RF Frequency = 900MHz (Note 6)
RF Frequency = 2000MHz (Note 6)
–28
–26
18
18
dBm
dBm
RF Input Resistance
Referenced to VCC
350
Ω
150
●
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Specifications over the – 40°C to 85°C operating temperature range
are assured by design, characterization and correlation with statistical
process controls.
Note 3: Slew rate is measured open loop. The slew time at VPCA/B is
measured between 1V and 2V.
Note 4: Maximum DAC zero-scale offset voltage that can be applied to PCTL.
TYP
250
Note 5: This is the time from SHDN rising edge 50% switch point to
VPCA = 0.25V.
Note 6: Guaranteed by design. This parameter is not production tested.
Note 7: Includes maximum DAC offset voltage and maximum control
voltage.
Note 8: Bandwidth is calculated using the 10% to 90% rise time:
BW = 0.35/rise time
Note 9: Measured 12µs after SHDN = HI.
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10000
75°C
25°C
–30°C
1000
100
10
1
–28
–22 –16 –10 –4
2
8
RF INPUT POWER (dBm)
14
4401 G01
LTC4400-1 Detector Characteristics
at 1800MHz
10000
75°C
25°C
–30°C
1000
100
10
1
–26 –20
–14 –8
–2
4
10
RF INPUT POWER (dBm)
16
4401 G02
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
LTC4400-1 Detector Characteristics
at 900MHz
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
TYPICAL PERFOR A CE CHARACTERISTICS
LTC4400-1 Detector Characteristics
at 2400MHz
10000
75°C
25°C
–30°C
1000
100
10
1
–24 –20 –16 –12 –8 –4 0 4 8
RF INPUT POWER (dBm)
12 16
4401 G03
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LTC4400-1/LTC4400-2
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10000
75°C
25°C
–30°C
1000
100
10
1
–22 –18 –14 –10 –6 –2 2 6
RF INPUT POWER (dBm)
10 14
LTC4400-2 Detector Characteristics
at 900MHz
10000
75°C
25°C
–30°C
1000
100
10
1
–28
–22 –16 –10 –4
2
8
RF INPUT POWER (dBm)
4401 G04
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PI FU CTIO S
14
4400 G05
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
LTC4400-1 Detector Characteristics
at 2700MHz
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
TYPICAL PERFOR A CE CHARACTERISTICS
LTC4400-2 Detector Characteristics
at 1800MHz
10000
75°C
25°C
–30°C
1000
100
10
1
–26 –20
–14 –8
–2
4
10
RF INPUT POWER (dBm)
16
4400 G06
(LTC4400-1/LTC4400-2)
RF (Pins 1/8): RF Feedback Voltage. This input is referenced
to VCC. The frequency range is 300MHz to 2700MHz for the
LTC4400-1 and 300MHz to 2000MHz for the LTC4400-2.
This pin has an internal 250Ω termination, an internal
Schottky diode detector and peak detector capacitor.
SHDN (Pins 4/6): Shutdown Input. A logic low on the SHDN
pin places the part in shutdown mode. A logic high places
the part in enable mode. SHDN has an internal 150k pulldown resistor to ensure that the part is in shutdown when
the drivers are in a three-state condition.
GND (Pins 2/4): System Ground.
VPCA (Pins 5/2): Power Control Voltage Output. This pin
drives an external RF power amplifier power control pin.
The maximum load capacitance is 100pF.
PCTL (Pins 3/5): Analog Input. The external power control
DAC drives this input. The amplifier servos the RF power
until the RF detected signal equals the DAC signal. The
input impedance is typically 90kΩ.
VPCB (Pin 3): (LTC4400-2 Only) Power Control Voltage
Output. This pin drives an external RF power amplifier
power control pin. The maximum load capacitance is
100pF.
VCC (Pins 6/1): Input Supply Voltage, 2.7V to 6V. VCC
should be bypassed with 0.1µF and 100pF ceramic capacitors. Used as return for RF 250Ω termination.
BSEL (Pin 7): (LTC4400-2 Only) Selects VPCA when Low
and VPCB when High. This input has an internal 150k
resistor to ground.
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LTC4400-1/LTC4400-2
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BLOCK DIAGRA
(LTC4400-1)
68Ω
RF IN
33pF
RF PA
50Ω
Li-Ion
VCC
6
TXENB
AUTOZERO
–
AZ
+
+
–
GAIN
COMPRESSION
GM
+
250Ω
RF
1
+
–
30k
28pF
30k
60µA
GND
CLAMP
80mV
+
270kHz
FILTER
+
CC
5
BUFFER
38k
–
RF DET
VPCA
30k
–
60µA
22k
VREF
51k
30k
+
2
–
33.4k
6k
12Ω
TXENB
VBG
VREF
10µs
DELAY
CONTROL
150k
100Ω
LTC4400-1
4
3
4400-1 BD
PCTL
SHDN
NOTE: THE DIRECTIONAL COUPLER SHOWN IN THIS FIGURE MAY BE REPLACED
WITH A COUPLING CAPACITOR AND RESISTOR AS DESCRIBED IN APPLICATION
NOTE 91 “LOW COST COUPLING METHODS FOR RF POWER DETECTORS REPLACE
DIRECTIONAL COUPLERS”
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LTC4400-1/LTC4400-2
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BLOCK DIAGRA
(LTC4400-2)
0.4pF
50Ω
DIPLEXER
900MHz
RF PA
1.8GHz/1.9GHz
RF PA
Li-Ion
VCC
1
TXENB
AUTOZERO
–
AZ
+
+
–
GAIN
COMPRESSION
BUF A
GM
+
250Ω
RF
8
+
–
30k
28pF
30k
60µA
GND
80mV
+
MUX1
MUX2
CC
38k
–
RF DET
30k
–
60µA
22k
VREF
51k
30k
+
4
12Ω
33.4k
VPCB
100Ω
6k
TXENB
VREF
3
BUF B
–
VBG
VPCA
CLAMP
270kHz
FILTER
+
2
12Ω
10µs
DELAY
VPCA
CONTROL
100Ω
150k
150k
LTC4400-2
6
5
7
SHDN
PCTL
BSEL
4400-2 BD
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LTC4400-1/LTC4400-2
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APPLICATIONS INFORMATION
Operation
The LTC4400-X RF power control amplifier integrates
several functions to provide RF power control over frequencies ranging from 300MHz to 2.7GHz. This product is
well suited to control RF power amplifiers that exhibit fast
turn-on times. The device also prevents damage to the RF
power amplifier due to overvoltage conditions. These
functions include an internally compensated power control amplifier to control the RF output power, an autozero
section to cancel internal and external voltage offsets, an
RF Schottky diode peak detector and amplifier to convert
the RF feedback signal to DC, a VPCA/B overvoltage clamp,
compression and a bandgap reference.
Band Selection
The LTC4400-2 is designed to drive two separate power
control lines. The BSEL pin will select VPCA when low and
VPCB when high. BSEL must be established prior to SHDN
being asserted high.
Control Amplifier
The control amplifier supplies the power control voltage to
the RF power amplifier. A portion (typically – 19dB for low
frequencies and –14dB for high frequencies) of the RF
output voltage is sampled, via a directional coupler or
capacitive tap, to close the gain control loop. When a DAC
voltage is applied to PCTL, the amplifier quickly servos
VPCA/B positive until the detected feedback voltage applied
to the RF pin matches the voltage at PCTL. This feedback
loop provides accurate RF power control. VPCA/B is capable
of driving a 6mA load current and 100pF load capacitor.
Control Amplifier Compression
The gain compression breakpoints are at PCTL = 80mV
and PCTL = 160mV. Above 160mV the gain does not
change. The compression changes the feedback attenuation these by reducing the loop gain.
power control loop. The RF pin input resistance is typically 250Ω and the frequency range of this pin is 300MHz
to 2700MHz for the LTC4400-1 and 300MHz to 2000MHz
for the LTC4400-2. The detector demonstrates excellent
efficiency over a wide range of input power. The Schottky
detector is biased at about 60µA and drives an on-chip
peak detector capacitor of 28pF.
Autozero
An autozero system is included to improve power programming accuracy over temperature. This section cancels internal offsets associated with the Schottky diode
detector and control amplifier. External offsets associated
with the DAC driving the PCTL pin are also cancelled.
Offset drift due to temperature is cancelled between each
burst. The maximum offset voltage allowed at the DAC
output is limited to 400mV. Autozeroing is performed
during a 10µs period after SHDN is asserted high. An
internal timer enables the VPCA/B output after 10µs. The
autozero capacitors are held and the VPCA/B pin is connected to the control amplifier output. The hold droop
voltage of typically < 1µV/ms provides for accurate offset
cancellation. The part should be shut down between
bursts or after multiple consecutive bursts.
Filter
There is a 270kHz two pole filter included in the PCTL path
to remove DAC noise.
Protection Features
The RF power amplifier control voltage pin is overvoltage
protected. The VPCA/B overvoltage clamp regulates
VPCA/B to 2.9V when the gain and PCTL input combination
attempts to exceed this voltage.
Modes of Operation
RF Detector
Shutdown: The part is in shutdown mode when SHDN is
low. VPCA/B is held at ground and the power supply current
is typically 10µA.
The internal RF Schottky diode peak detector and amplifier converts the RF feedback voltage to a low frequency
voltage. This voltage is compared to the DAC voltage at
the PCTL pin by the control amplifier to close the RF
Enable: When SHDN is asserted high the part will automatically calibrate out all offsets. This takes <10µs and is
controlled by an internal delay circuit. After 10µs VPCA/B
will step up to the starting voltage of 450mV. The user can
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LTC4400-1/LTC4400-2
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APPLICATIO S I FOR ATIO
then apply the ramp signal. The user should wait 12µs after
SHDN has been asserted high before applying the ramp.
The DAC should be settled 2µs after asserting SHDN high.
LTC4400-X Timing Diagram
T7
BSEL
T8
(LTC4400-2 ONLY)
2µs
10µs
28µs
543µs
28µs
SHDN
VPCA/B
VSTART
PCTL
4400 TA02
T1
T2 T3
T4
T5
T6
T1: LTC4400-X COMES OUT OF SHUTDOWN 12µs PRIOR TO BURST
T2: INTERNAL TIMER COMPLETES AUTOZERO CORRECTION, <10µs
T3: BASEBAND CONTROLLER STARTS RF POWER RAMP UP AT 12µs AFTER
SHDN IS ASSERTED HIGH
T4: BASEBAND CONTROLLER COMPLETES RAMP UP
T5: BASEBAND CONTROLLER STARTS RF POWER RAMP DOWN AT END OF BURST
T6: LTC4400-X RETURNS TO SHUTDOWN MODE BETWEEN BURSTS
T7: BSEL CHANGE PRIOR TO SHDN, 0ns TYPICAL (LTC4400-2 ONLY)
T8: BSEL CHANGE AFTER TO SHDN, 0ns TYPICAL (LTC4400-2 ONLY)
General Layout Considerations
The LTC4400-X should be placed near the coupling components. The feedback signal line to the RF pin should be
a 50Ω transmission line with optional termination or a
short line.
External Termination
The LTC4400-X has an internal 250Ω termination resistor
at the RF pin. If a directional coupler is used, it is recommended that an external 68Ω termination resistor be
connected between the RF coupling capacitor (33pF), and
ground at the side connected to the directional coupler.
Termination components should be placed adjacent to the
LTC4400-X. An alternative method couples RF from the
power amplifier to the power controller through a 0.4pF
±0.05pF capacitor and 50Ω series resistor, completely
eliminating the directional coupler.
Power Ramp Profiles
The external voltage gain associated with the RF channel
can vary significantly between RF power amplifier types.
The LTC4400-X frequency compensation has been
optimized to be stable with several different power amplifiers and manufacturers. This frequency compensation
generally defines the loop dynamics that impact the power/
time response and possibly (slow loops) the power ramp
sidebands. The LTC4400-X operates open loop until an RF
voltage appears at the RF pin, at which time the loop closes
and the output power follows the DAC profile. The RF
power amplifier will require a certain control voltage level
(threshold) before an RF output signal is produced. The
LTC4400-X VPCA/B output must quickly rise to this threshold voltage in order to meet the power/time profile. To
reduce this time, the LTC4400-X starts at 450mV. However, at very low power levels the PCTL input signal is
small, and the VPCA/B output may take several microseconds to reach the RF power amplifier threshold voltage. To
reduce this time, it may be necessary to apply a positive
pulse at the start of the ramp to quickly bring the VPCA/B
output to the threshold voltage. This can generally be
achieved with DAC programming. The magnitude of the
pulse is dependent on the RF amplifier characteristics.
Power ramp sidebands and power/time are also a factor
when ramping to zero power. When the power is ramped
down the loop will eventually open at power levels below
the LTC4400-X detector threshold. The LTC4400-X will
then go open loop and the output voltage at VPCA/B will
stop falling. If this voltage is high enough to produce RF
output power, the power/time or power ramp sidebands
may not meet specification. This problem can be avoided
by starting the DAC ramp from 100mV (Figure 1). At the
end of the cycle, the DAC can be ramped down to 0mV.
This applies a negative signal to the LTC4400-X thereby
ensuring that the VPCA/B output will ramp to 0V. The
100mV ramp step must be applied < 2µs after SHDN is
asserted high to allow the autozero to cancel the step. Slow
DAC rise times will extend this time by the additional RC
time constants which may require that the DAC is enabled
and settled prior to SHDN asserted high.
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LTC4400-1/LTC4400-2
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APPLICATIO S I FOR ATIO
1) The additional voltage gain supplied by the RF power
amplifier increases the loop gain raising poles normally
below the 0dB axis. The extra voltage gain can vary
significantly over input/output power ranges, frequency,
power supply, temperature and manufacturer. RF power
amplifier gain control transfer functions are often not
available and must be generated by the user. Loop oscillations are most likely to occur in the midpower range
where the external voltage gain associated with the RF
power amplifier typically peaks. It is useful to measure the
oscillation or ringing frequency to determine whether it
corresponds to the expected loop bandwidth and thus is
due to high gain bandwidth.
10
0
RFOUT (dBc)
–10
–20
–30
–40
–50
–60
–70
–80
–28
–18
–10
0
543
553
561
571
DAC VOLTAGE
TIME (µs)
START
PULSE
START
CODE
ZERO
CODE
100mV
SHDN
12µs, ALLOWS TIME FOR DAC
AND AUTOZERO TO SETTLE
4400 F01
Figure 1. LTC4400-X Ramp Timing
Demo Board
The LTC4400-X demo board is available upon request. The
demo board has a 900MHz and an 1800MHz RF channel
controlled by the LTC4400-X. Timing signals for SHDN are
generated on the board using a 13MHz crystal reference.
The PCTL power control pin is driven by a 10-bit DAC and
the DAC profile can be loaded via a serial port. The serial
port data is stored in a flash memory which is capable of
storing eight ramp profiles. The board is supplied preloaded
with four GSM power profiles and four DCS power profiles
covering the entire power range. External timing signals
can be used in place of the internal crystal controlled
timing. A variety of RF power amplifiers as well as ramp
generation software are available.
LTC4400-X Control Loop Stability
The LTC4400-X provides a stable control loop for several
RF power amplifier models from different manufacturers
over a wide range of frequencies, output power levels and
VSWR conditions. However, there are several factors that
can improve or degrade loop frequency stability.
2) Loop voltage losses supplied by the RF feedback
coupler will improve phase margin. The larger the loss, the
more stable the loop will become. However, larger losses
reduce the RF signal to the LTC4400-X and detector
performance may be degraded at low power levels. (See
RF Detector Characteristics.)
3) Additional poles within the loop due to filtering or the
turn-on response of the RF power amplifier can degrade
the phase margin if these pole frequencies are near the
effective loop bandwidth frequency. Generally loops using
RF power amplifiers with fast turn-on times have more
phase margin. Extra filtering below 16MHz should never
be placed within the control loop, as this will only degrade
phase margin.
4) Control loop instability can also be due to open-loop
issues. RF power amplifiers should first be characterized
in an open-loop configuration to ensure self oscillation is
not present. Self-oscillation is often related to poor power
supply decoupling, ground loops, coupling due to poor
layout and extreme VSWR conditions. The oscillation frequency is generally in the 100kHz to 10MHz range. Power
supply related oscillation suppression requires large value
ceramic decoupling capacitors placed close to the RF
power amp supply pins. The range of decoupling capacitor
values is typically 1nF to 3.3µF.
5) Poor layout techniques associated with the RF coupling
components may result in high frequency signals bypassing the coupler. This could result in stability problems due
to the reduction in the coupler loss.
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LTC4400-1/LTC4400-2
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APPLICATIO S I FOR ATIO
Determining External Loop Gain and Bandwidth
The external loop voltage gain contributed by the RF channel and RF feedback coupling network should be measured in a closed-loop configuration. A voltage step is
applied to PCTL and the change in VPCA/B is measured. The
detected voltage is K • PCTL, where K is the internal gain
between PCTL and the RF pin, and the external voltage gain
contributed by the RF power amplifier and RF feedback
coupling network is K • ∆VPCTL/∆VVPC. Measuring voltage
gain in the closed-loop configuration accounts for the
nonlinear detector gain that is dependent on RF input
voltage and frequency.
The LTC4400-X unity gain bandwidth specified in the data
sheet assumes that the net voltage gain contributed by the
RF power amplifier and RF feedback coupler is unity. The
bandwidth is calculated by measuring the rise time between 10% and 90% of the voltage change at VPCA/B for a
small step in voltage applied to PCTL.
BW1 = 0.35/rise time
The LTC4400-X control amplifier unity gain bandwidth
(BW1) is typically 450kHz below a PCTL voltage of 80mV.
For PCTL voltages < 80mV, the RF detected voltage is
0.6PCTL. For PCTL voltages >160mV, RF detected voltage
is 1.22PCTL – 0.1. This change in gain is due to an internal
compression circuit designed to extend the detector range.
160
140
120
100
80
60
40
20
0
–20
–40
–60
–80
–100
–120
10M
External pole frequencies within the loop will further
reduce phase margin. The phase margin degradation, due
to external and internal pole combinations, is difficult to
determine since complex poles are present. Gain peaking
may occur, resulting in higher bandwidth and lower phase
margin than predicted from the open-loop Bode plot. A
low frequency AC SPICE model of the LTC4400-X power
controller is included to better determine pole and zero
interactions. The user can apply external gains and poles
to determine bandwidth and phase margin. DC, transient
and RF information cannot be extracted from the present
model. The model is suitable for external gain evaluations
up to 6 ×. The 270kHz PCTL input filter limits the bandwidth, therefore, use the RF input as demonstrated in the
model. Gain compression is not modeled.
PHASE
GAIN
1k
10k
100k
FREQUENCY (Hz)
1M
4400 F02
Figure 2. Measured Open-Loop Gain and Phase, PCTL < 80mV
VOLTAGE GAIN (dB)
RLOAD = 2k
CLOAD = 33pF
80
70
60
50
40
30
20
10
0
–10
–20
–30
–40
–50
–60
100
180
160
140
120
100
80
60
40
20
0
–20
–40
–60
–80
–100
10M
RLOAD = 2k
CLOAD = 33pF
PHASE
GAIN
1k
10k
100k
FREQUENCY (Hz)
1M
PHASE (DEG)
80
70
60
50
40
30
20
10
0
–10
–20
–30
–40
–50
–60
100
PHASE (DEG)
VOLTAGE GAIN (dB)
For example, to determine the external RF channel loop
voltage gain with the loop closed, apply a 100mV step to
PCTL from 300mV to 400mV. VPCA/B will increase to
supply enough feedback voltage to the RF pin to cancel
this 100mV step which would be the required detected
voltage step of 122mV. VPCA/B changed from 1.5V to
1.561V to create the RF output power change required.
The net external voltage gain contributed by the RF power
amplifier and RF feedback coupling network can be calculated by dividing the 122mV change at the RF pin by the
61mV change at the VPCA/B pin. The net external voltage
gain would then be approximately 2. The loop bandwidth
extends to 2 • BW1. If BW1 is 230kHz, the loop bandwidth
increases to approximately 460kHz. The phase margin can
be determined from Figures 2 and 3. Repeat the above
voltage gain measurement over the full power and frequency range.
4400 F03
Figure 3. Measured Open-Loop Gain and Phase, PCTL > 160mV
sn4400 4400fas
10
LTC4400-1/LTC4400-2
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APPLICATIO S I FOR ATIO
Users should note very carefully the following factors
regarding this model: Model performance in general will
reflect typical baseline specs for a given device, and
certain aspects of performance may not be modeled fully.
While reasonable care has been taken in the preparation,
we cannot be responsible for correct application on any
and all computer systems. Model users are hereby notified
that these models are supplied “as is”, with no direct or
implied responsibility on the part of LTC for their operation
within a customer circuit or system. Further, Linear Technology Corporation reserves the right to change these
models without prior notice.
CONTROL
AMPLIFER
RF POWER AMP
+
CONTROLLED
RF OUTPUT
POWER
VPC
PCTL
G1
G2
–
IFB
LTC4400-X
H1
RF
H2
4400 F04
RF DETECTOR
The user agrees that this model is licensed from Linear
Technology and agrees that the model may be used,
loaned, given away or included in other model libraries as
long as this notice and the model in its entirety and
unchanged is included. No right to make derivative works
or modifications to the model is granted hereby. All such
rights are reserved.
This model is provided as is. Linear Technology makes
no warranty, either expressed or implied about the suitability or fitness of this model for any particular purpose.
In no event will Linear Technology be liable for special,
collateral, incidental or consequential damages in connection with or arising out of the use of this model. It
should be remembered that models are a simplification
of the actual circuit.
80
70
60
50
40
30
20
10
0
–10
–20
–30
–40
–50
–60
100
1k
180
RLOAD = 2k
160
CLOAD = 33pF
140
120
PHASE
100
80
60
GAIN
40
20
0
–20
–40
–60
–80
–100
10k
100k
1M
10M
FREQUENCY (Hz)
PHASE (DEG)
In all cases, the current data sheet information is your final
design guideline, and is the only performance guarantee.
For further technical information, refer to individual device
data sheets. Your feedback and suggestions on this model
is appreciated.
Linear Technology Corporation hereby grants the users of
this model a nonexclusive, nontransferable license to use
this model under the following conditions:
VOLTAGE GAIN (dB)
This model (Figure 6) is being supplied to LTC users as an
aid to circuit designs. While the model reflects reasonably
close similarity to corresponding devices in low frequency
AC performance terms, its use is not suggested as a
replacement for breadboarding. Simulation should be
used as a forerunner or a supplement to traditional lab
testing.
4400 F05
RF COUPLER
14dB to 20dB LOSS
Figure 4. Closed-Loop Block Diagram
Figure 5. SPICE Model Open-Loop Gain and Phase
Characteristics from RF to VPCA, PCTL < 80mV
sn4400 4400fas
11
LTC4400-1/LTC4400-2
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APPLICATIO S I FOR ATIO
*LTC4400-X Low Frequency AC Spice Model*
*July 11, 2001
*Main Network Description
GGIN1 ND3 0 ND2 IFB 86E-6
GGXFB IFB 0 0 ND12 33E-6
GGX5 ND11 0 0 ND10 1E-6
GGX6 ND12 0 0 ND11 1E-6
GGX1 ND4 0 0 ND3 1E-6
GGX2 ND6 0 0 ND4 1E-6
GGX3 ND7 0 0 ND6 1E-6
GGX4 ND8 0 0 ND7 1E-6
EEX1 ND9 0 0 ND8 2
CCC1 ND3 0 44E-12
CCPCTL2 ND2 0 7E-12
CCPCTL1 ND1 0 13E-12
CCLINT VPCA 0 5E-12
CCLOAD VPCA 0 33E-12
CCFB1 IFB 0 2.4E-12
CCX5 ND11 0 16E-15
CCX6 ND12 0 1.2E-15
CCP ND10 0 28E-12
CCX2 ND6 0 8E-15
CCX3 ND7 0 32E-15
LLX1 ND5 0 80E-3
RR01 ND3 0 20E6
RRFILT ND2 ND1 44E3
RRPCTL1 PCTL ND1 51E3
RRPCTL2 ND1 0 38E3
RR9 VPCA ND9 50
RRLOAD VPCA 0 2E3
RRFB1 IFB 0 22E3
RRT RF 0 250
RRX5 ND11 0 1E6
RRX6 ND12 0 1E6
RRSDRF ND10 500
RRX1 ND4 ND5 1E6
RRX2 ND6 0 1E6
RRX3 ND7 0 1E6
RRX4 ND8 0 1E6
**Closed-loop feedback, comment-out VPCTLO, VRF, Adjust EFB gain to reflect external gain, currently set at 3X**
*EFB RF 0 VPCA VIN 3
*VIN VIN 0 DC 0 AC 1
*VPCTLO PCTL 0 DC 0
**Open-loop connections, comment-out EFB, VIN and VPCTLO******
VPCTLO PCTL 0 DC 0
VRF RF 0 DC 0 AC 1
******Add AC statement and print statement as required***
.AC DEC 50 100 1E7
*****for PSPICE only*****
.OP
.PROBE
*************************
.END
Figure 6. LTC4400-X Low Frequency AC SPICE Model
sn4400 4400fas
12
LTC4400-1/LTC4400-2
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APPLICATIO S I FOR ATIO
PCTL
RPCTL1
51E3
ND3
ND1
CPCTL1
13E-12
ND2
+
RFILT
44E3
RPCTL2
38E3 C
PCTL2
7E-12
–
86E-6
GX1
+
RO1
20E6
GM
ND6
ND4
GIN1
GM
–
CC1
44E-12
1E-6
RX1
1E6
ND5
GX2
+
LX1
80E-3
–
+
RX2
1E6
GM
1E-6
–
IFB
1E-6
GX4
+
RX3
1E6
GM
CX2
8E-15
ND8
ND7
GX3
RX4
1E6
GM
–
CX3
32E-15
1E-6
ND8
2X BUFFER
RF
ND11
RT
250Ω
RX5
1E6
GM
ND10
CP
28E-12
GX5
+
RSD
500Ω
–
1E-6
ND12
RX6
1E6
GM
–
CX5
16E-15
GX6
+
1E-6
33E-6
EX1
+
RFB1
22E3
GM
–
CX6
1.2E-15
GXFB
+
R9
50Ω
VAMP
CFB1
2.4E-12
–
2
CLINT
5E-12
ND9
VPCA
RLOAD
2E3
CLOAD
33E-12
4400 F07
Figure 7. LTC4400-X Low Frequency AC Model
sn4400 4400fas
13
LTC4400-1/LTC4400-2
U
PACKAGE DESCRIPTIO
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
0.62
MAX
2.90 BSC
(NOTE 4)
0.95
REF
1.22 REF
3.85 MAX 2.62 REF
1.4 MIN
2.80 BSC
1.50 – 1.75
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.30 – 0.45
6 PLCS (NOTE 3)
0.95 BSC
0.80 – 0.90
0.20 BSC
0.01 – 0.10
1.00 MAX
DATUM ‘A’
0.30 – 0.50 REF
0.09 – 0.20
(NOTE 3)
1.90 BSC
S6 TSOT-23 0302
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
sn4400 4400fas
14
LTC4400-1/LTC4400-2
U
PACKAGE DESCRIPTIO
MS8 Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
0.889 ± 0.127
(.035 ± .005)
5.23
(.206)
MIN
3.2 – 3.45
(.126 – .136)
0.42 ± 0.04
(.0165 ± .0015)
TYP
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.65
(.0256)
BSC
8
7 6 5
0.52
(.206)
REF
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
3.00 ± 0.102
(.118 ± .004)
NOTE 4
4.90 ± 0.15
(1.93 ± .006)
DETAIL “A”
0° – 6° TYP
GAUGE PLANE
0.53 ± 0.015
(.021 ± .006)
DETAIL “A”
1
2 3
4
1.10
(.043)
MAX
0.86
(.034)
REF
0.18
(.077)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
0.65
(.0256)
BSC
0.13 ± 0.076
(.005 ± .003)
MSOP (MS8) 0802
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
sn4400 4400fas
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC4400-1/LTC4400-2
U
TYPICAL APPLICATION
LTC4400-2 Dual Band Cellular Telephone Transmitter
68Ω
33pF
LTC4400-2
VIN
VCC
RF
Li-Ion SHDN
SHDN
VPCA
BSEL
BSEL
VPCB
GND
PCTL
0.1µF
900MHz
DIRECTIONAL
COUPLER
DIPLEXER
RF PA
50Ω
DAC
1.8GHz/
1.9GHz
RF PA
4400 TA03
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
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Regulated –5V from 3V, REG Pin Indicates Regulation, Up to 15mA, Micropower
LTC1732
Li-Ion Linear Charger
Complete Linear Charger for 1- and 2-Cell Li-Ion Battery
LTC1734/LTC1734L
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Only Two External Components, No Reverse Current Protection Diode Required,
No Sense Resistor Required, PROG Voltage for Charge Termination
LTC1754
ThinSOT Charge Pump
2V ≤ VIN ≤ 4V, IOUT = 40mA, No Inductors for White LED Backlight
LTC1757A
RF Power Controller
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LTC1758
RF Power Controller
Single/Dual Band GSM/DCS/GPRS Mobile Phones
LTC1957
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Complete Pulse Charger for 1-Cell Li-Ion Battery
LTC4401
SOT-23 RF PA Controller
Multiband GSM/DCS/GPRS Phones, 45dB Dynamic Range, 250kHz Loop BW
LT 5500
1.8GHz to 2.7GHz Receiver Front End
Dual LNA Gain Setting +13.5dB/–14dB at 2.5GHz, Double-Balanced Mixer,
1.8V ≤ VSUPPLY ≤ 5.25V
LT5502
400MHz Quadrature IF Demodulator with
RSSI
70MHz to 400MHz IF, 1.8V ≤ VSUPPLY ≤ 5.25V, 84dBm Limiting Gain,
90dB RSSI Range
LT5503
1.2GHz to 2.7GHz Direct IQ Modulator with
Mixer
Direct IQ Modulator with Integrated 90° Phase Shifter, 4-Step RF Power Control,
1.8V ≤ VSUPPLY ≤ 5.25V
LT5504
800MHz to 2.7GHz RF Measuring Receiver
80dB Dynamic Range, Temperature Compensated, 2.7V to 5.5V Supply
LTC5505
300MHz to 3.5GHz RF Power Detector
>40dB Dynamic Range, Temperature Compensated, 2.7V to 6V Supply
LTC5507
100kHz to 1GHz RF Power Detector
40dB Dynamic Range, Temperature Compensated, 2.7V to 6V Supply
LTC5508
300MHz to 7GHz RF Power Detector
40dB Dynamic Range, 2.7V to 6V Supply, SC70 Package
LT5511
High Signal Level Up Converting Mixer
RF Output to 3GHz, 17dBm IIP3, Integrated LO Buffer
LT5512
High Signal Level Down Converting Mixer
DC-3GHz RF Input, 20dBm IIP3, Integrated LO Buffer
®
sn4400 4400fas
16
Linear Technology Corporation
LT/TP 0403 1K REV A • PRINTED IN THE USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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 LINEAR TECHNOLOGY CORPORATION 2001