1957f.pm6
1
LTC1957-1/LTC1957-2
Single/Dual Band RF Power
Controllers with 40dB Dynamic Range
The LTC
1957-2 is a dual band RF power controller for
power amplifiers operating in the 850MHz to 2GHz 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 inte-
grated in one small 10-pin MSOP package, thereby
minimizing PCB area.
The LTC1957-1 is a single output RF power controller
that is identical in performance to the LTC1957-2 except
that one output (V
PCA
) is provided. The LTC1957-1 can
be used to drive a single RF 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 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 (LTC1957-2)
s
Internal Schottky Diode Detector with Improved
Dynamic Range vs the LTC1757A
s
Wide Input Frequency Range: 850MHz to 2GHz
s
Autozero Loop Cancels Offset Errors and
Temperature Dependent Offsets
s
Wide V
IN
Range: 2.7V to 6V
s
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
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 (LTC1957-1)
and 10-Pin MSOP (LTC1957-2)
s
Pin Compatible with the LTC1757A-X
s
Improved Start Voltage Accuracy and Range
s
Improved PCTL Input Filtering
, 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
LTC1957-2
33pF
68
V
IN
Li-Ion
SHDN
BSEL
TXEN
900MHz
DAC
RF PA
DIRECTIONAL
COUPLER
DIPLEXER
1.8GHz /1.9GHz
RF PA
50
1957 TA01
LTC1957-2 Dual Band Cellular Telephone Transmitter
s
Single and Dual Band GSM/GPRS Cellular Telephones
s
PCS Devices
s
Wireless Data Modems
s
U.S. TDMA Cellular Phones
APPLICATIO S
U
FEATURES
TYPICAL APPLICATIO
U
DESCRIPTIO
U
2
LTC1957-1/LTC1957-2
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
LTC1957-2EMS
LTRJ
T
JMAX
= 125
C,
JA
= 160
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
LTC1957-1EMS8
LTRH
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
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
1
1.6
mA
I
VIN
Operating Current
SHDN = HI, TXEN = HI, I
VPCA
= I
VPCB
= 0mA, V
PCA/B
= HI
1.1
1.7
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
, PCTL = 2V, External Gain = 0.417
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
= 2.6V, V
IN
= 3V
q
6.0
10
mA
V
PCA/B
Enable Time
V
PCTL
= 2V Step, C
LOAD
= 100pF (Note 5)
q
440
650
ns
V
PCA/B
Bandwidth
C
LOAD
= 100pF, R
LOAD
= 400
(Note 8)
q
280
370
500
kHz
V
PCA/B
Load Capacitance
(Note 6)
100
pF
V
PCA/B
Slew Rate
V
PCTL
= 2V Step, C
LOAD
= 100pF (Note 3)
q
1.2
2.2
V/
s
V
PCA/B
Droop
V
IN
= 2.7V, V
PCTL
= 2V Step
1
V/ms
V
PCA/B
TXEN Start Voltage
Open Loop, TXEN Low to High, C
LOAD
= 100pF (Note 9)
500
600
700
mV
T
JMAX
= 125
C,
JA
= 160
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
ABSOLUTE AXI U RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
ELECTRICAL CHARACTERISTICS
Consult LTC Marketing for parts specified with wider operating temperature ranges.
3
LTC1957-1/LTC1957-2
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
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 6V
q
0.35
1.4
V
SHDN, TXEN, BSEL Input Current
SHDN, TXEN or BSEL = 3.6V
q
10
25
50
A
PCTL Input Voltage Control Range
V
IN
= 3V to 6V, R
LOAD
= 400
q
0
2
V
PCTL Input Voltage Range
V
IN
= 3V, R
LOAD
= 400
(Note 7)
q
2.4
V
PCTL Input Resistance
SHDN = LO, TXEN = LO
q
50
90
140
k
PCTL Input Filter
350
kHz
Autozero Range
V
IN
= 2.7V, R
LOAD
= 400
(Note 4)
q
400
mV
Autozero Settling Time (t
S
)
t
S
, Shutdown to Enable (Autozero), V
IN
= 2.7V (Note 10)
q
50
s
RF Input Frequency Range
(Note 6)
q
850
2000
MHz
RF Input Power Range
900MHz (Note 6)
26
16
dBm
1800MHz (Note 6)
24
16
dBm
RF Input Impedance
Referenced to V
IN
, SHDN = LO, TXEN = LO
q
100
200
350
BSEL Timing
t
1
, Setup Time Prior to TXEN Asserted High
200
ns
t
2
, Hold Time After TXEN is Asserted Low
200
ns
ELECTRICAL C
C
HARA TERISTICS
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 = V
IN
, unless otherwise noted.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC1957-1 and LTC1957-2 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: 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 1
s after TXEN = HI.
Note 10: 50% switch point, SHDN HI = V
IN
, TXEN HI = V
IN
.
4
LTC1957-1/LTC1957-2
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 200
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 200
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): (LTC1957-2 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 impedance is typically 90k
.
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): (LTC1957-2 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 (LTC1957-2 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.
(LTC1957-2/LTC1957-1)
U
U
U
PI FU CTIO S
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Detector Characteristics
at 900MHz
Detector Characteristics
at 1800MHz
RF INPUT POWER (dBm)
10
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
100
1000
10000
26
14
8
2
4
10
1
20
16
1957 G01
V
IN
= 3V TO 4.4V
30
C
75
C
25
C
RF INPUT POWER (dBm)
10
PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)
100
1000
10000
24
16 12 8 4
0
4
8
1
20
12 16
1957 G02
V
IN
= 3V TO 4.4V
30
C
75
C
25
C
5
LTC1957-1/LTC1957-2
BLOCK DIAGRA
W
+
RFDET
+
CAMP
C
C
50mV
FILTER
ICL
1.2V
22k
33k
+
+
CS
35k
22k
33k
22k
110k
140k
1.2V
ADJUSTABLE
100
METAL
35k
V
IN
200
200
R
SENSE
0.05
METAL
PROGRAMMABLE
28pF
33pF
12
100
TSDB
TXENI
100
1957 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
AUTOZERO
TXENB
PA
PB
ADJUSTABLE
+
MUX
CONTROL
TXEN
7
3
SHDN
BG1
1.2V BANDGAP
COMPRESSION
TSDB
BG1
THERMAL
SHUTDOWN
RF PA
DIPLEXER
1.8GHz/1.9GHz
50
5
XMT AUTOZERO
400
A
68
(LTC1957-2)
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