www.docs.chipfind.ru
1
LTC1757A-1/LTC1757A-2
Single/Dual Band
RF Power Controllers
April 2000
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 < 1
A.
s
Dual Band RF Power Amplifier Control (LTC1757A-2)
s
Improved Internal Schottky Diode Detector
s
Wide Input Frequency Range: 850MHz to 2GHz
s
Autozero Cancels Initial Offsets and Temperature
Dependent Offset Errors
s
Wide V
IN
Range of 2.7V to 6V Allows
Direct Connection to Battery
s
RF Output Power Set by External DAC
s
Fast Acquire After Transmit Enable
s
Internal Frequency Compensation
s
Rail-to-Rail Power Control Outputs
s
RF PA Supply Current Limiting
s
Battery Overvoltage Protection
s
Power Control Signal Overvoltage Protection
s
Low Operating Current: 1mA
s
Very Low Shutdown Current: < 1
A
s
Available in a 8-Pin MSOP Package (LTC1757A-1)
and 10-Pin MSOP (LTC1757A-2)
, LTC and LT are registered trademarks of Linear Technology Corporation.
V
IN
RF
SHDN
BSEL
GND
10
9
8
7
6
1
2
3
4
5
V
CC
V
PCA
V
PCB
TXEN
PCTL
LTC1757A-2
V
IN
Li-Ion
SHDN
BSEL
TXEN
900MHz
DAC
RF PA
DIRECTIONAL
COUPLER
DIPLEXER
1.8GHz /1.9GHz
RF PA
50
1757A TA01
33pF
68
LTC1757A-2 Dual Band Cellular Telephone Transmitter
s
Single and Dual Band GSM Cellular Telephones
s
PCS Devices
s
Wireless Data Modems
s
TDMA Cellular Telephones
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 represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
Final Electrical Specifications
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LTC1757A-1/LT1757A-2
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)
ORDER PART
NUMBER
MS10 PART MARKING
Consult factory for Industrial and Military grade parts.
LTC1757A-2EMS
LTPM
T
JMAX
= 125
C,
JA
= 250
C/W
1
2
3
4
5
V
IN
RF
SHDN
BSEL
GND
10
9
8
7
6
V
CC
V
PCA
V
PCB
TXEN
PCTL
TOP VIEW
MS10 PACKAGE
10-LEAD PLASTIC MSOP
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
(Note 1)
ORDER PART
NUMBER
MS8 PART MARKING
LTC1757A-1EMS8
LTPL
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.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Operating Voltage
(Note 7)
q
2.7
6
V
I
VIN
Shutdown Current
SHDN = LO, TXEN = LO, BSEL = LO
q
1
A
I
VIN
Autozero Current
SHDN = HI, TXEN = LO
q
0.9
1.5
mA
I
VIN
Operating Current
SHDN = HI, TXEN = HI, I
VPCA
= I
VPCB
= 0mA, V
PCA/B
= HI
q
1
1.6
mA
I
VCC
Current Limit
2.2
A
V
IN
to V
CC
Resistance
SHDN = LO, TXEN = LO
90
150
m
V
PCA/B
V
OL
TXEN = HI, Open Loop, PCTL = 100mV
q
0
0.1
V
V
PCA/B
Dropout Voltage
I
LOAD
= 5.5mA, V
IN
= 2.7V
q
V
IN
0.28
V
V
PCA/B
Voltage Clamp
R
LOAD
= 400
q
2.7
2.85
3.0
V
V
PCA/B
Output Current
V
PCA/B
= 2.4V, V
IN
= 2.7V
q
5.5
9
mA
V
PCA/B
Enable Time
V
PCTL
= 2V Step, C
LOAD
= 100pF (Note 5)
200
ns
V
PCA/B
Bandwidth
C
LOAD
= 100pF, R
LOAD
= 400
(Note 9)
q
250
400
550
kHz
V
PCA/B
Load Capacitance
(Note 6)
100
pF
V
PCA/B
Slew Rate
V
PCTL
= 2V Step, C
LOAD
= 100pF (Note 3)
1.5
3
V/
s
V
PCA/B
Droop
V
IN
= 2.7V, V
PCTL
= 2V Step
10
V/ms
V
PCA/B
TXEN Start Voltage
Open Loop, TXEN Low to High, C
LOAD
= 100pF (Note 10)
400
550
700
mV
SHDN Input Threshold
V
IN
= 2.7V to 6V, TXEN = LO
q
0.35
1.4
V
TXEN, BSEL Input Threshold
V
IN
= 2.7V to 4.7V
q
0.35
1.4
V
T
JMAX
= 150
C,
JA
= 250
C/W
1
2
3
4
V
IN
RF
SHDN
GND
8
7
6
5
V
CC
V
PCA
TXEN
PCTL
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
ELECTRICAL CHARACTERISTICS
PACKAGE/ORDER I FOR ATIO
U
U
W
ABSOLUTE AXI U RATI GS
W
W
W
U
3
LTC1757A-1/LTC1757A-2
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.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SHDN, TXEN, BSEL Input Current
SHDN, TXEN or BSEL = 3.6V
q
10
30
50
A
PCTL Input Voltage Control Range
V
IN
= 2.7V to 4.7V, R
LOAD
= 400
q
0
2
V
PCTL Input Voltage Range
V
IN
= 3V, R
LOAD
= 400
(Note 8)
q
2.4
V
PCTL Input Resistance
SHDN = LO, TXEN = LO
q
50
100
150
k
PCTL Input Filter
1.25
MHz
Autozero Range
V
IN
= 2.7V, R
LOAD
= 400
(Note 4)
q
400
mV
Autozero Settling Time (t
S
)
Shutdown to Enable (Autozero), V
IN
= 2.7V (Note 11)
q
50
s
RF Input Frequency Range
(Note 6)
q
850
2000
MHz
RF Input Power Range
900MHz (Note 6)
24
16
dBm
1800MHz (Note 6)
22
16
dBm
RF DC Input Resistance
Referenced to V
IN
, SHDN = LO, TXEN = LO
q
100
175
250
V
IN
Overvoltage Range
V
PCA/B
< 0.5V, R
LOAD
= 400
q
4.8
5.0
5.4
V
BSEL Timing
t
1
, Setup Time Prior to TXEN Asserted High
200
ns
t
2
, Hold Time After TXEN is Asserted Low
200
ns
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 1
s after TXEN = HI.
Note 11: 50% switch point, SHDN HI = V
IN
, TXEN HI = V
IN
.
ELECTRICAL CHARACTERISTICS
4
LTC1757A-1/LT1757A-2
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
RF Detector Characteristics
at 900MHz
RF INPUT POWER (dBm)
10
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
100
1000
10000
22
14 10 6
2
2
6
10
1
18
14
1757A G02
V
IN
= 3V TO 4.4V
30
C
75
C
25
C
V
IN
(Pin 1): Input Supply Voltage, 2.7V to 6V. V
IN
should
be bypassed with 0.1
F and 100pF ceramic capacitors.
Used as return for RF 175
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 175
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.
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 0.050
sense resistor between V
IN
and
V
CC
that senses the RF power amplifier supply current to
detect overcurrent conditions.
(LTC1757A-2/LTC1757A-1)
RF Detector Characteristics
at 1800MHz
U
U
U
PI FU CTIO S
RF INPUT POWER (dBm)
10
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
100
1000
10000
24
12
16
8 4
8
4
0
12
1
20
16
1757A G01
V
IN
= 3V TO 4.4V
30
C
75
C
25
C
5
LTC1757A-1/LTC1757A-2
+
RFDET
+
CAMP
C
C
50mV
ICL
1.2V
33k
+
+
CS
42k
16.7k
33k
33k
110k
140k
1.2V
600mV
100
METAL
42k
V
IN
175
R
SENSE
0.05
METAL
68
600mV
22pF
33pF
6pF
54.5k
173k
12
100
TSDB
TXENI
100
1757A BD
12
150k
150k
150k
OPERATE SHDN
BSEL
PB
PA
OFFSET
TRIM
GAIN
TRIM
OVERCURRENT
60
A
60
A
RF
2
V
CC
0.02
0.02
10
V
IN
Li-Ion
1
V
PCA
9
V
PCB
8
GND
4
PCTL
6
g
m
RF PA
900MHz
AZ
g
m
VPC
OVP
g
m
V
IN
ADJ
AUTOZERO
TXENB
PA
PB
+
+
MUX
CONTROL
TXEN
7
3
SHDN
BG1
1.2V BANDGAP
TSDB
BG1
THERMAL
SHUTDOWN
RF PA
DIPLEXER
1.8GHz
50
5
XMT AUTOZERO
400
A
(LTC1757A-2)
BLOCK DIAGRA
W
PDF 
ZIP