LTC1757A-1/LTC1757A-2
Single/Dual Band
RF Power Controllers
FEATURES
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DESCRIPTIO
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Dual Band RF Power Amplifier Control (LTC1757A-2)
Improved Internal Schottky Diode Detector
Wide Input Frequency Range: 850MHz to 2GHz
Autozero Cancels Initial Offsets and Temperature
Dependent Offset Errors
Wide V
IN
Range of 2.7V to 6V Allows
Direct Connection to Battery
RF Output Power Set by External DAC
Fast Acquire After Transmit Enable
Internal Frequency Compensation
Rail-to-Rail Power Control Outputs
RF PA Supply Current Limiting
Battery Overvoltage Protection
Power Control Signal Overvoltage Protection
Low Operating Current: 1mA
Very Low Shutdown Current: < 1µA
Available in a 8-Pin MSOP Package (LTC1757A-1)
and 10-Pin MSOP (LTC1757A-2)
The LTC
®
1757A-2 is a dual band RF power controller for
RF power amplifiers operating in the 850MHz to 2GHz
range. The LTC1757A is pin compatible with the LTC1757
but has improved RF detection range. The input voltage
range is optimized for operation from a single lithium-ion
cell or 3× NiMH. Several functions required for RF power
control and protection are integrated in one small 10-pin
MSOP package, thereby minimizing PCB area.
The LTC1757A-1 is a single output RF power controller
that is identical in performance to the LTC1757A-2 except
that one output (V
PCA
) is provided. The LTC1757A-1 can
be used to drive a single RF channel or dual channel
module with integral multiplexer. This part is available in
an 8-pin MSOP package.
RF power is controlled by driving the RF amplifier power
control pins and sensing the resultant RF output power
via a directional coupler. The RF sense 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 supply voltage and current and
high power control pin voltages.
Internal and external offsets are cancelled over tempera-
ture by an autozero control loop, allowing accurate low
power programming. The shutdown feature disables the
part and reduces the supply current to < 1µA.
APPLICATIO S
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Single/Dual Band GSM Cellular Telephones
PCS Devices
Wireless Data Modems
TDMA Cellular Telephones
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
68Ω
V
IN
33pF
Li-Ion
SHDN
BSEL
LTC1757A-2 Dual Band Cellular Telephone Transmitter
LTC1757A-2
1
2
3
4
5
V
IN
RF
SHDN
BSEL
GND
V
CC
V
PCA
V
PCB
TXEN
PCTL
10
9
8
7
6
900MHz
TXEN
RF PA
DIRECTIONAL
COUPLER
DIPLEXER
DAC
1.8GHz /1.9GHz
RF PA
U
50Ω
1757A TA01
U
U
1
LTC1757A-1/LTC1757A-2
ABSOLUTE
AXI U
RATI GS
V
IN
to GND ............................................... – 0.3V to 6.5V
V
PCA
, V
PCB
Voltage ..................................... – 0.3V to 3V
PCTL Voltage ............................... – 0.3V to (V
IN
+ 0.3V)
RF Voltage ........................................ (V
IN
– 2.2V) to 7V
I
VCC
, Continuous ....................................................... 1A
I
VCC
, 12.5% Duty Cycle .......................................... 2.5A
SHDN, TXEN, BSEL
Voltage to GND ............................ – 0.3V to (V
IN
+ 0.3V)
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
IN
RF
SHDN
GND
1
2
3
4
8
7
6
5
V
CC
V
PCA
TXEN
PCTL
ORDER PART
NUMBER
LTC1757A-1EMS8
MS8 PART MARKING
LTPL
V
IN
RF
SHDN
BSEL
GND
1
2
3
4
5
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 250°C/W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
PARAMETER
V
IN
Operating Voltage
I
VIN
Shutdown Current
I
VIN
Autozero Current
I
VIN
Operating Current
I
VCC
Current Limit
V
IN
to V
CC
Resistance
V
PCA/B
V
OL
V
PCA/B
Dropout Voltage
V
PCA/B
Voltage Clamp
V
PCA/B
Output Current
V
PCA/B
Enable Time
V
PCA/B
Bandwidth
V
PCA/B
Load Capacitance
V
PCA/B
Slew Rate
V
PCA/B
Droop
V
PCA/B
TXEN Start Voltage
SHDN Input Threshold
TXEN, BSEL Input Threshold
SHDN = LO, TXEN = LO
CONDITIONS
(Note 7)
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, SHDN = TXEN = HI, unless otherwise noted.
MIN
q
q
q
q
SHDN = LO, TXEN = LO, BSEL = LO
SHDN = HI, TXEN = LO
SHDN = HI, TXEN = HI, I
VPCA
= I
VPCB
= 0mA, V
PCA/B
= HI
TXEN = HI, Open Loop, PCTL = – 100mV
I
LOAD
= 5.5mA, V
IN
= 2.7V
R
LOAD
= 400Ω
V
PCA/B
= 2.4V, V
IN
= 2.7V
V
PCTL
= 2V Step, C
LOAD
= 100pF (Note 5)
C
LOAD
= 100pF, R
LOAD
= 400Ω (Note 9)
(Note 6)
V
PCTL
= 2V Step, C
LOAD
= 100pF (Note 3)
V
IN
= 2.7V, V
PCTL
= 2V Step
Open Loop, TXEN Low to High, C
LOAD
= 100pF (Note 10)
V
IN
= 2.7V to 6V, TXEN = LO
V
IN
= 2.7V to 4.7V
2
U
U
W
W W
U
W
(Note 1)
I
VPCA/B
, 25% Duty Cycle ...................................... 20mA
Operating Temperature Range
(Note 2) ................................................. – 30°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Maximum Junction Temperature ........................ 125°C
Lead Temperature (Soldering, 10 sec)................ 300°C
TOP VIEW
10
9
8
7
6
V
CC
V
PCA
V
PCB
TXEN
PCTL
ORDER PART
NUMBER
LTC1757A-2EMS
MS10 PART MARKING
LTPM
MS10 PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 250°C/W
TYP
MAX
6
1
UNITS
V
µA
mA
mA
A
mΩ
V
V
V
mA
ns
2.7
0.9
1
2.2
90
1.5
1.6
150
0.1
V
IN
– 0.28
3.0
q
q
q
q
0
2.7
5.5
250
1.5
400
2.85
9
200
400
3
±10
550
q
550
100
kHz
pF
V/µs
µV/ms
700
1.4
1.4
mV
V
V
q
q
0.35
0.35
LTC1757A-1/LTC1757A-2
ELECTRICAL CHARACTERISTICS
PARAMETER
SHDN, TXEN, BSEL Input Current
PCTL Input Voltage Control Range
PCTL Input Voltage Range
PCTL Input Resistance
PCTL Input Filter
Autozero Range
Autozero Settling Time (t
S
)
RF Input Frequency Range
RF Input Power Range
RF DC Input Resistance
V
IN
Overvoltage Range
BSEL Timing
CONDITIONS
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, SHDN = TXEN = HI, unless otherwise noted.
MIN
q
q
q
q
TYP
30
MAX
50
2
2.4
UNITS
µA
V
V
kΩ
MHz
mV
µs
MHz
dBm
dBm
Ω
V
ns
ns
SHDN, TXEN or BSEL = 3.6V
V
IN
= 2.7V to 4.7V, R
LOAD
= 400Ω
V
IN
= 3V, R
LOAD
= 400Ω (Note 8)
SHDN = LO, TXEN = LO
V
IN
= 2.7V, R
LOAD
= 400Ω (Note 4)
Shutdown to Enable (Autozero), V
IN
= 2.7V (Note 11)
(Note 6)
900MHz (Note 6)
1800MHz (Note 6)
Referenced to V
IN
, SHDN = LO, TXEN = LO
V
PCA/B
< 0.5V, R
LOAD
= 400Ω
t
1
, Setup Time Prior to TXEN Asserted High
t
2
, Hold Time After TXEN is Asserted Low
10
0
50
100
1.25
150
400
50
q
q
q
850
– 24
–22
2000
16
16
185
5.0
200
200
300
5.4
q
q
100
4.8
Note 1:
Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.
Note 2:
The LTC1757A-1 and LTC1757A-2 are guaranteed to meet performance
specifications from 0°C to 70°C. Specifications over the – 30°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 V
PCA
or V
PCB
is
measured between 1V and 2V.
Note 4:
Maximum DAC zero-scale offset voltage that can be applied to PCTL.
Note 5:
This is the time from TXEN rising edge 50% switch point to
V
PCA/B
= 1V.
Note 6:
Guaranteed by design. This parameter is not production tested.
Note 7:
For V
IN
voltages greater than 4.7V, V
PCA
/V
PCB
are set low by the
overvoltage shutdown.
Note 8:
Includes maximum DAC offset voltage and maximum control voltage.
Note 9:
Bandwidth is calculated using the 10% to 90% rise time equation:
BW = 0.35/rise time
Note 10:
Measured 1µs after TXEN = HI.
Note 11:
50% switch point, SHDN HI = V
IN
, TXEN HI = V
IN
.
3
LTC1757A-1/LTC1757A-2
TYPICAL PERFOR A CE CHARACTERISTICS
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
10000
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
RF Detector Characteristics
at 900MHz
V
IN
= 3V TO 4.4V
1000
100
10
–30°C
25°C
1
–24 –20 –16 –12 –8 –4 0 4 8
RF INPUT POWER (dBm)
12 16
1757A G01
PI FU CTIO S
(LTC1757A-2/LTC1757A-1)
V
IN
(Pin 1):
Input Supply Voltage, 2.7V to 6V. V
IN
should
be bypassed with 0.1µF and 100pF ceramic capacitors.
Used as return for RF 185Ω termination.
RF (Pin 2):
RF Feedback Voltage from the Directional
Coupler. Referenced to V
IN
. A coupling capacitor of 33pF
must be used to connect to the ground referenced direc-
tional coupler. The frequency range is 850MHz to 2000MHz.
This pin has an internal 185Ω termination, an internal
Schottky diode detector and peak detector capacitor.
SHDN (Pin 3):
Shutdown Input. A logic low on the SHDN
pin places the part in shutdown mode. A logic high places
the part in autozero when TXEN is low. SHDN has an inter-
nal 150k pull-down resistor to ensure that the part is in shut-
down when the drivers are in a three-state condition.
BSEL (Pin 4): (LTC1757A-2 Only)
Selects V
PCA
when low
and V
PCB
when high. This input has an internal 150k
resistor to ground.
GND (Pin 5/Pin 4):
System Ground.
PCTL (Pin 6/Pin 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 resistance is typically 100k.
4
U W
75°C
RF Detector Characteristics
at 1800MHz
10000
V
IN
= 3V TO 4.4V
1000
100
10
–30°C
75°C
25°C
1
–22 –18 –14 –10 –6 –2 2 6
RF INPUT POWER (dBm)
10 14
1757A G02
U
U
U
TXEN (Pin 7/Pin 6):
Transmit Enable Input. A logic high
enables the control amplifier. When TXEN is low and
SHDN is high the part is in the autozero mode. This input
has an internal 150k resistor to ground.
V
PCB
(Pin 8): (LTC1757A-2 Only)
Power Control Voltage
Output. This pin drives an external RF power amplifier
power control pin. The maximum load capacitance is
100pF. The output is capable of rail-to-rail swings at low
load currents. Selected when BSEL is high.
V
PCA
(Pin 9/Pin 7):
Power Control Voltage Output. This pin
drives an external RF power amplifier power control pin.
The maximum load capacitance is 100pF. The output is
capable of rail-to-rail swings at low load currents. Selected
when BSEL is low (LTC1757A-2 only).
V
CC
(Pin 10/Pin 8):
RF Power Amplifier Supply. This pin
has an internal 0.050Ω sense resistor between V
IN
and
V
CC
that senses the RF power amplifier supply current to
detect overcurrent conditions.
LTC1757A-1/LTC1757A-2
BLOCK DIAGRA
10
V
CC
0.02Ω
R
SENSE
0.05Ω
METAL
68Ω
–
CS
33pF
+
OFFSET
TRIM
V
IN
600mV
GAIN
TRIM
g
m
50mV
2
RF
185Ω
22pF
42k
60µA
5
GND
60µA
BG1
THERMAL
SHUTDOWN
OPERATE SHDN
150k
W
42k
3
(LTC1757A-2)
DIPLEXER
900MHz
RF PA
50Ω
RF PA
1.8GHz
Li-Ion
1
V
IN
0.02Ω
TXENB
100Ω
METAL
AUTOZERO
–
AZ
PA
V
PCA
9
OVERCURRENT
+
+
–
+
CAMP
PB
ADJ
–+
6pF
ICL
–
C
C
400µA
140k
V
PCB
8
+
RFDET
33k
VPC
g
m
110k
–
16.7k
33k
1.2V
OVP
g
m
BG1
1.2V BANDGAP
1.2V
600mV
33k
54.5k
12Ω
TSDB
TSDB
TXENI
150k
MUX
CONTROL
PA
PB
100Ω
12Ω
100Ω
173k
V
IN
XMT AUTOZERO
150k
SHDN
7
TXEN
6
PCTL
4
BSEL
1757A BD
5
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