Linear Technology LTC1758-1EMS8 Datasheet

250kHz Control Loop Bandwidth and

FEATURES

■

Dual Band RF Power Amplifier Control (LTC1758-2)

■

Internal Schottky Diode Detector with Improved
Dynamic Range vs LTC1757A

■

Wide Input Frequency Range: 850MHz to 2GHz

■

Autozero Loop Cancels Offset Errors and
Temperature Dependent Offsets

■

Wide VIN Range: 2.7V to 6V
Allows Direct Connection to Battery

■

RF Output Power Set by External DAC

■

250kHz Control Loop Bandwidth

■

Fast Acquire After Transmit Enable

■

Internal Frequency Compensation

■

Rail-to-Rail Power Control Outputs

■

Power Control Signal Overvoltage Protection

■

Low Operating Current: 1mA

■

Very Low Shutdown Current: <1µA

■

Available in 8-Pin MSOP (LTC1758-1)
and 10-Pin MSOP (LTC1758-2) Packages

■

Pin Compatible with LTC1757A-X

■

Improved Start Voltage Accuracy

■

Improved PCTL Input Filtering

U

APPLICATIO S

■

Single and Dual Band GSM/GPRS Cellular Telephones

■

PCS Devices

■

Wireless Data Modems

■

U.S. TDMA Cellular Phones

LTC1758-1/LTC1758-2

RF Power Controllers with

40dB Dynamic Range

U

DESCRIPTIO

The LTC®1758-2 is a dual band RF power controller for
RF power amplifiers operating in the 850MHz to 2GHz
range. The loop bandwidth reduction to 250kHz im­proves frequency stability when controlling slow turn-on
PAs such as the Philips BGY280, Conexant RM009/
CX77302, Anadigics AWT6102/AWT6107 and the Hitachi
PF08107/PF08123B.

The LTC1758-1 is a single output RF power controller
that is identical in performance to the LTC1758-2 except
that one output (V
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 tempera­ture by an autozero control loop, allowing accurate low
power programming. The shutdown feature disables the
part and reduces the supply current to <1µA.

, LTC and LT are registered trademarks of Linear Technology Corporation.

) is provided. The LTC1758-1 can

PCA

TYPICAL APPLICATIO

68Ω

33pF

V

IN

Li-Ion

SHDN

BSEL

U

LTC1758-2 Dual Band Cellular Telephone Transmitter

LTC1758-2

1

V

IN

2

RF

3

SHDN

4

BSEL

5

GND

DAC

V

V

PCA

V

PCB

TXEN
PCTL

10

CC

9
8
7

TXEN

6

900MHz

1.8GHz/1.9GHz RF PA

RF PA

DIRECTIONAL

COUPLER

DIPLEXER

50Ω

1758 TA01

1

LTC1758-1/LTC1758-2

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

WWWU

ABSOLUTE AXI U RATI GS

(Note 1)

VIN to GND............................................... –0.3V to 6.5V

V

, V

PCA

Voltage ..................................... – 0.3V to 3V

PCB

PCTL Voltage ............................... –0.3V to (VIN + 0.3V)

RF Voltage ........................................ (VIN – 2.2V) to 7V

I

, Continuous....................................................... 1A

VCC

I

, 12.5% Duty Cycle.......................................... 2.5A

VCC

SHDN, TXEN, BSEL

Voltage to GND ............................ –0.3V to (VIN + 0.3V)

UU

W

PACKAGE/ORDER I FOR ATIO

TOP VIEW

V

1

IN

2

RF

3

SHDN

4

GND

MS8 PACKAGE

8-LEAD PLASTIC MSOP

T

= 125°C, θJA = 160°C/W

JMAX

Consult LTC Marketing for parts specified with wider operating temperature ranges.

8
7
6
5

V

CC

V

PCA

TXEN
PCTL

ORDER PART

NUMBER

LTC1758-1EMS8

MS8 PART MARKING

LTSL

I

, 25% Duty Cycle ...................................... 20mA

VPCA/B

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

ORDER PART

NUMBER

LTC1758-2EMS

T

= 125°C, θJA = 160°C/W

JMAX

MS10 PART MARKING

LTSM

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, SHDN = TXEN = HI, unless otherwise noted.

PARAMETER CONDITIONS MIN TYP MAX UNITS

VIN Operating Voltage ● 2.7 6 V
I

Shutdown Current SHDN = LO, TXEN = LO, BSEL = LO ● 1 µA

VIN

I

Autozero Current SHDN = HI, TXEN = LO ● 1 1.6 mA

VIN

I

Operating Current SHDN = HI, TXEN = HI, I

VIN

I

Current Limit 2.2 A

VCC

VIN to VCC Resistance SHDN = LO, TXEN = LO 90 150 mΩ
V

PCA/B VOL

V

Dropout Voltage I

PCA/B

V

Voltage Clamp R

PCA/B

V

Output Current V

PCA/B

V

Enable Time V

PCA/B

V

Bandwidth C

PCA/B

V

Load Capacitance (Note 6) 100 pF

PCA/B

V

Slew Rate V

PCA/B

V

Droop VIN = 2.7V, V

PCA/B

V

TXEN Start Voltage Open Loop, TXEN Low to High, C

PCA/B

SHDN Input Threshold VIN = 2.7V to 6V, TXEN = LO ● 0.35 1.4 V
TXEN, BSEL Input Threshold VIN = 2.7V to 6V ● 0.35 1.4 V

2

TXEN = HI, Open Loop, PCTL = –100mV ● 0 0.1 V

= 5.5mA, VIN = 2.7V ● VIN – 0.28 V

LOAD

= 400Ω, PCTL = 2V, External Gain = 0.417 ● 2.7 2.85 3.0 V

LOAD

= 2.4V, VIN = 2.7V ● 5.5 9 mA

PCA/B

V

= 2.6V, VIN = 3V ● 610 mA

PCA/B

= 2V Step, C

PCTL

= 100pF, R

LOAD

= 2V Step, C

PCTL

LOAD

LOAD

LOAD

= 2V Step ±1 µV/ms

PCTL

= I

VPCA

= 100pF (Note 5) ● 620 1000 ns

= 400Ω (Note 8) ● 180 250 330 kHz

= 100pF (Note 3) ● 0.75 1.3 V/µs

= 0mA, V

VPCB

= 100pF (Note 9) 500 600 700 mV

LOAD

= HI 1.1 1.7 mA

PCA/B

LTC1758-1/LTC1758-2

LECTRICAL C CHARA TERIST

E

ICS

The ● denotes specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, SHDN = TXEN = VIN, unless otherwise noted.

PARAMETER CONDITIONS MIN TYP MAX UNITS

SHDN, TXEN, BSEL Input Current SHDN, TXEN or BSEL = 3.6V ● 10 25 50 µA
PCTL Input Voltage Control Range VIN = 3V to 6V, R
PCTL Input Voltage Range VIN = 3V, R

LOAD

PCTL Input Resistance SHDN = LO, TXEN = LO ● 50 90 140 kΩ
PCTL Input Filter 350 kHz
Autozero Range VIN = 2.7V, R
Autozero Settling Time (tS)t

, Shutdown to Enable (Autozero), VIN = 2.7V (Note 10) ● 50 µs

S

RF Input Frequency Range (Note 6) ● 850 2000 MHz
RF Input Power Range 900MHz (Note 6) –26 16 dBm

1800MHz (Note 6) –24 16 dBm
RF Input Impedance Referenced to VIN, SHDN = LO, TXEN = LO ● 100 200 350 Ω
BSEL Timing t1, Setup Time Prior to TXEN Asserted High 200 ns

, Hold Time After TXEN is Asserted Low 200 ns

t

2

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

Note 2: The LTC1758-1 and LTC1758-2 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
measured between 1V and 2V.

Note 4: Maximum DAC zero-scale offset voltage that can be applied to
PCTL.

= 400Ω ● 02V

LOAD

= 400Ω (Note 7) ● 2.4 V

= 400Ω (Note 4) ● 400 mV

LOAD

Note 5: This is the time from TXEN rising edge 50% switch point to
V

= 1V.

PCA/B

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:

or V

PCB

is

BW = 0.35/rise time

PCA

Note 9: Measured 1µs after TXEN = HI.
Note 10: 50% switch point, SHDN HI = V

, TXEN HI = VIN.

IN

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TYPICAL PERFOR A CE CHARACTERISTICS

RF Detector Characteristics
at 900MHz

10000

VIN = 3V TO 4.4V

1000

100

–30°C

10

1

–26 –14 –8 –2 4 10

PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)

75°C
25°C

–20

RF INPUT POWER (dBm)

16

1758 G01

RF Detector Characteristics
at 1800MHz

10000

VIN = 3V TO 4.4V

1000

100

–30°C

10

1

–24 –16 –12 –8 –4 0 4 8

PCTL REFERENCED DETECTOR OUTPUT VOLTAGE (mV)

–20

25°C

75°C

12 16

RF INPUT POWER (dBm)

1758 G02

3

LTC1758-1/LTC1758-2

U

PI FU CTIO S

VIN (Pin 1): Input Supply Voltage, 2.7V to 6V. VIN should
be bypassed with 0.1µF and 100pF ceramic capacitors.
Used as return for RF 200Ω termination.

RF (Pin 2): RF Feedback Voltage from the Directional
Coupler. Referenced to VIN. A coupling capacitor of 33pF
must be used to connect to the ground referenced direc­tional coupler. The frequency range is 850MHz to 2000MHz.
This pin has an internal 200Ω 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 inter­nal 150k pull-down resistor to ensure that the part is in shut­down when the drivers are in a three-state condition.

BSEL (Pin 4): (LTC1758-2 Only) Selects V
and V
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

when high. This input has an internal 150k

PCB

UU

(LTC1758-2/LTC1758-1)

when low

PCA

power until the RF detected signal equals the DAC signal.
The input impedance is typically 90kΩ.

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

(Pin 8): (LTC1758-2 Only) Power Control Voltage

PCB

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

(Pin 9/Pin 7): Power Control Voltage Output. This pin

PCA

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 (LTC1758-2 only).

VCC (Pin 10/Pin 8): RF Power Amplifier Supply. This pin
has an internal 0.090Ω sense resistor between VIN and
VCC that senses the RF power amplifier supply current to
detect overcurrent conditions.

4

BLOCK DIAGRA

LTC1758-1/LTC1758-2

W

(LTC1758-2)

DIPLEXER

68Ω

33pF

10

V

CC

R

SENSE

0.02Ω 0.02Ω

0.05Ω

METAL

–

CS

+

OFFSET
TRIM

V

IN

RF

2

GND

5

200Ω

28pF

60µA60µA

BG1

THERMAL

SHUTDOWN

OPERATE SHDN

1

V

100Ω
METAL

OVERCURRENT

PROGRAMMABLE

200Ω

35k

35k

TSDB

Li-Ion

IN

GAIN
TRIM

+

RFDET

–

COMPRESSION

XMT AUTOZERO

RF PA900MHz

50Ω

AUTOZERO

TXENB

–

AZ

+

g

m

50mV FILTER

+

–

ICL

33k

22k

33k

22k

22k

+

CAMP

–

BG1

1.2V BANDGAP

TXENI

150k150k150k

RF PA

ADJUSTABLE

C

C

VPC

MUX

CONTROL

1.8GHz/1.9GHz

400µA

g

m

1.2V

ADJUSTABLE

PB

PA

PA

V

PCA

9

PB

140k

110k

1.2V

12Ω

100ΩTSDB

12Ω

100Ω

V

PCB

8

SHDN

TXEN

73

PCTL

6

BSEL

4

1758 BD

5