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EVALUATION KIT AVAILABLE
TCM850 TCM851 TCM852 TCM853
1
REGULATED GaAs FET BIAS SUPPLY
FEATURES
s s s Fixed - 4.1V or Adjustable - 0.5V to - 9V Output at 5mA 4.5V to 10V Input Voltage Range Low Output Voltage Ripple TCM850-852 .............................................. 2mVp-p TCM853 ...................................................... 1mVp-p 100kHz Charge Pump Switching Frequency Optional External Synchronizing Clock Input (TCM852) Logic Level Shutdown Mode ................ 0.5A Typ. Temperature (TCM850/852/853) Low Cost, 8-Pin SOIC Package
GENERAL DESCRIPTION
The TCM850/1/2/3 combines an inverting charge pump and a low noise linear regulator in a single small outline package. They are ideal for biasing GaAS FETs in cellular telephone transmitter power amplifiers All four devices accept a range of input voltages from 4.5V to 10.0V and have - 5mA output current capability. The TCM850/1/2 have both preset (- 4.1V) and variable (- 0.5V to -9.0V) output voltages that program with an external resistor divider. The TCM853 output voltage programs with an external positive control voltage. The TCM850/1/3 can be shutdown reducing quiescent current to less than 0.5A (typ) over temperature, 2A (typ) for the TCM851.
2 3 4 5 6 7
s s s s
ORDERING INFORMATION APPLICATIONS
s s s s s Cellular Phones Negative Regulated Power Supplies LCD Bias Contrast Control Adjustable GaAs FET Bias Wireless Data Loggers Part No. TCM850COA TCM850EOA TCM851COA TCM851EOA TCM852COA TCM852EOA TCM853COA TCM853EOA TCM850EV FUNCTIONAL BLOCK DIAGRAM
+ C1 + C1
Package 8-Pin SOIC 8-Pin SOIC 8-Pin SOIC 8-Pin SOIC
Temp. Range 0C to +70C - 40C to +85C 0C to +70C - 40C to +85C
8-Pin SOIC 0C to +70C 8-Pin SOIC - 40C to +85C 8-Pin SOIC 0C to +70C 8-Pin SOIC - 40C to +85C Evaluation Kit for TCM850/1/2/3
C1
- C1
CHARGE PUMP C3 TCM850 TCM851 TCM852
IN
C1
- C1
CHARGE PUMP C3 TCM853
IN
NEGOUT C2 SHDN (TCM850) SHDN (TCM851) OSC (TCM852)
N
OUT C4
NEGOUT C2
N C4
OUT
- 1.28V REF
GND
Figure 1.
TELCOM SEMICONDUCTOR, INC.
-
CONT (CONTROL VOLTAGE) GND
TC850/1/2/3-3 10/1/96
FB (GND to SET VOUT = - 4.1V)
SHDN
-
+
+
8
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TCM850 TCM851 TCM852 TCM853
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (VIN to GND) .................. - 0.3V to +10.5V VNEGOUT to GND ...................................... - 10.5V to 0.3V VIN to VNEGOUT ............................................................... - 0.3 to 21V VOUT to GND** ........................................ VNEGOUT to 0.3V SHDN or OSC (Pin 4) to GND ........ - 0.3V to (VIN + 0.3V) Power Dissipation (TA < 70C) SOIC ...........................................................470mW Operating Temperature Range C Device .............................................. 0C to 70C E Device ....................................... - 40C to +85C Storage Temperature Range ................ - 65C to +165C Lead Temperature (Soldering, 10 sec) ................. +300C
REGULATED GaAs FET BIAS SUPPLY
*This is a stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. Exposure to Absolute Maximum Rating Conditions for extended periods may affect device reliability. **The output may be shorted to NEGOUT or GND if the package power dissipation is not exceeded. Typical short circuit current to GND is 50mA.
ELECTRICAL CHARACTERISTICS: VIN between +5V and +10V; VOUT = - 4.1V; RL = Open Circuit; TA = TMIN to
TMAX unless otherwise noted. A 100kHz, 50% duty cycle square wave between GND and VIN is applied to the OSC pin of the TCM852. Symbol
VIN VOUT
Parameter
Supply Voltage Output Voltage Output Voltage Range Set Voltage Supply Current Shutdown Supply Current
Test Conditions
Note 1 TCM850-TCM852: VFB = 0V (Note 3) TCM853: VCTRL = 4.1V TCM850-852: No Load TCM850/853: VIN = 10V, SHDN = 0V TCM851: SHDN = 2V TCM852: OSC Low TCM850-TCM852: VFB = 0V (Note 3) TCM853: VCTRL = 4.1V TCM850-TCM852 TCM853 TCM850-TCM853: TA = 25C (Note 2) Pin 4 Pin 4 Pin 4 Pin 4
Min
5 - 4.3 - 4.2
Typ
Max
Unit
VFBSET IQ ISHUT
VOUT Load Regulation VOUT Ripple fOSC VIH VIL IIN CIN Oscillator Frequency Input High Voltage Input Low Voltage Input Current Input Capacitance
-- 10 V - 4.1 - 3.9 V -- -4 - 0.5 to - (VIN -1) V - 1.32 - 1.28 - 1.24 V -- 2 3 mA -- 0.5 -- A -- 2 -- -- 0.5 -- -- 4 8 mV/mA -- 3 8 -- 2 -- mVp-p -- 1 -- 80 100 120 kHz 2 -- -- V -- -- 0.5 V -- -- 1 A -- 10 -- pF
NOTES: 1. The supply voltage can drop to 4.5V, but the output is no longer guaranteed to sink 5mA at - 4.1V. 2. The TCM852 will operate with a 50kHz to 250kHz square wave of 40% to 60% duty cycle. For best performance, use an 80kHz to 120kHz square wave with 50% duty cycle. 3. IOUT = 0mA or 5mA. Reference Figures 3 and 5.
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TELCOM SEMICONDUCTOR, INC.
REGULATED GaAs FET BIAS SUPPLY TCM850 TCM851 TCM852 TCM853
PIN CONFIGURATIONS 8-Pin SOIC
C1+ C1- NEGOUT SHDN 1 2 3 4 8 7 TCM850COA TCM850EOA 6 5 IN GND C1+ C1- 1 2 3 4 TCM851COA TCM851EOA 8 7 6 5 IN GND C1+ C1- 1 2 3 4 TCM852COA TCM852EOA 8 7 6 5 IN GND OUT FB C1+ C1- NEGOUT SHDN 1 2 3 4 8 7 TCM853COA TCM853EOA 6 5 IN GND OUT CONT
1
2 3
Description
C1 positive input terminal. C1 negative input terminal. Negative (unregulated) output voltage. Shutdown input (TTL active LOW). Shutdown input (TTL active HIGH). External oscillator input. Feedback input. OUT is preset to - 4.1V when FB is grounded. OUT may be adjusted to other voltages by connecting a resistor divider as shown in Figure 4. Control input. VOUT is adjusted with a positive control voltage (0V to 10V) applied to this input through a resistive divider (Figure 5). Output voltage terminal. Ground. Positive power supply input voltage (4.5V to 10V).
OUT NEGOUT FB SHDN
OUT NEGOUT FB OSC
Figure 2.
PIN DESCRIPTION
Pin No (TCM850)
1 2 3 4 -- -- 5
Pin No (TCM851)
1 2 3 -- 4 -- 5
Pin No (TCM852)
1 2 3 -- -- 4 5
Pin No (TCM853)
1 2 3 4 -- -- --
Symbol
+ C1 - C1
NEGOUT SHDN SHDN OSC FB
4 5 6 7
--
--
--
5
CONT
6 7 8
6 7 8
6 7 8
6 7 8
OUT GND IN
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TELCOM SEMICONDUCTOR, INC.
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REGULATED GaAs FET BIAS SUPPLY TCM850 TCM851 TCM852 TCM853
DETAILED DEVICE DESCRIPTION
The voltage applied to VIN is inverted by a capacitive charge pump (using commutating capacitor C1 and reservoir capacitor C2). The negative voltage at NEGOUT is then regulated by an internal linear regulator, the output of which is connected to the OUT pin (Figure 1). The most negative output voltage possible is the inverted input voltage (i.e. -VIN) plus 1.0V (required by the post regulator). The linear regulator reduces combined output noise (charge pump ripple plus incoming supply noise) to 2mVp-p for the TCM850/ 1/2 and 1mVp-p for the TCM853.
C3 C1 C- 1 TCM850 TCM851 TCM852 VIN
IOUT
C+ 1 OUT VOUT = -2.56V C4 10F
NEGOUT C2 SHDN SHDN OSC GND FB
R2 = 100k
APPLICATIONS INFORMATION Setting the Output Voltage
The TCM850/1/2 operate in the fixed output voltage mode (OUT = - 4.1V) when the FB input is grounded (Figure 3). The output voltage can be adjusted by connecting FB to the midpoint of a resistive voltage divider from OUT to GND (Figure 4). Care must be taken to allow a minimum of 1.0V across the linear regulator for proper regulation. The output voltage is calculated using the formula below (R2 should be chosen to be between 100k and 400k): VOUT = (-1.28) 1+
R1 = 100k
All caps = 1.0F unless otherwise noted
Figure 4. TCM850/851/852 Adjustable Application
The relationship between output voltage and control voltage for the TCM853 (Figure 5) is given by: VOUT = VCTRL (-1.28)
()
VIN
R2 R1
()
R2 R1
VIN
C3 C1
IOUT
C+ 1 C- 1 OUT TCM850 TCM851 TCM852 VOUT = -4.1V C4 10F
C3 C1
IOUT
C+ 1 - C1 TCM853 NEGOUT OUT VOUT = - 0.5V to - 9.0V C4 10F
NEGOUT C2 SHDN SHDN OSC GND FB
C2
R2 = 100k
SHDN
CONT
GND
R1 = 100k
VCTRL (0 to 10V) All caps = 1.0F unless otherwise noted
All caps = 1.0F unless otherwise noted
Figure 3. TCM850/851/852 Standard Application 4-30
Figure 5. TCM853 Standard Application Circuit
TELCOM SEMICONDUCTOR, INC.
REGULATED GaAs FET BIAS SUPPLY TCM850 TCM851 TCM852 TCM853
Shutdown Mode
Shutdown inputs are provided to reduce TCM850/1/3 supply current during idle periods. When the shutdown input is in its active state, supply current over temperature is reduced to 0.5A (typ) TCM850/2/3 and 2A (typ) TCM851. All shutdown inputs are TTL level compatible: TCM850 and TCM853 both have active low inputs (SHDN) while the TCM851 has an active high input. The TCM852 can be shutdown by setting the OSC input to a logic low level. The TCM852 exits the shutdown state when the clock signal is again restored.
1
Noise and Ripple Measurement
The TCM850/1/2/3 charge pump switching action causes small ground voltage differences between the TCM850/1/2 /3 circuit and the oscilloscope. These voltage differences cause ground currents in the probe wires inducing voltage spikes and result in erroneous readings. As a result, noise and ripple measurements should be made directly across output capacitor C4. Do not use the ground lead of the oscilloscope probe. Instead, remove the plastic cover from the probe tip and touch the probe ground ring directly to the negative side of C4. Tektronix chassis mount test jack (part number 131-0258) or a nail-type probe tip connect to the probe and minimize noise and ripple measurement error.
2 3 4 5 6 7
Charge Pump Frequency Control
In applications where the charge pump switching frequency may cause interference or filtering problems, it is recommended the TCM852 be used. Switching frequency is determined by a 50kHz to 250kHz square wave signal applied to the OSC input. The signal applied to OSC can have a duty cycle between 40% and 60%. *Note: an external oscillator signal MUST be applied to the TCM852. The TCM852 does not have an on-board oscillator truebase.
Evaluation Kit
TelCom Semiconductor offers evaluation kit (TCM850EV) for the TCM850-853. A second evaluation kit (TC7660EV) evaluates several TelCom charge pumps including the TC7660, TC7660S, TC7662B, TC962, TC682. This kit also supports the TCM850 (but not the TCM851853).
Capacitors
Capacitors with low effective series resistance (ESR) should be used to maintain sufficient headroom across the linear post regulator. Recommended values for C1, C2, and C3 are 1F, 0.8 ESR. The recommended value for C4 is 10F, 0.2. All capacitors should be either surface mount chip tantalum, or chip ceramic types.
Board Layout
The TCM850/1/2/3 typically finds use in applications where low output noise is important. To ensure good noise performance, please observe the following basic layout suggestions: (1) Mount all components in the circuit as close together as possible. (2) Keep trace lengths short; especially those to control inputs such as FB and CONT. This will reduce the effect of parasitic capacitance and inductance. (3) Minimize ground impedance by employing a ground plane.
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TELCOM SEMICONDUCTOR, INC.
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REGULATED GaAs FET BIAS SUPPLY TCM850 TCM851 TCM852 TCM853
TYPICAL CHARACTERISTICS
Output Voltage vs. Output Current -4.06 VIN = 6V -4.07 -4.07 -4.06 IOUT = 3mA Output Voltage vs. Input Voltage Over Temperature
SUPPLY VOLTAGE
OUTPUT VOLTAGE
TA = 85C -4.08
TA = -40C
-4.08
-4.09
-4.09 TA = 25C -4.10
-4.10
-4.11 0 1 2 3 4 5 6 7 8 9 10 OUTPUT CURRENT (mA) Maximum Output Current vs. Input Voltage 80
-4.11 5 6 7 8 9 10 INPUT VOLTAGE (V) No-Load Supply Current vs. Input Voltage 2.0
MAXIMUM OUTPUT CURRENT (mA)
70 60 50 40 30 20 10 0 5.0 0.5 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 5 6 INPUT VOLTAGE (V) 8 7 INPUT VOLTAGE (V) 9 10
SUPPLY CURRENT (mA)
Supply Current vs. Temperature
1.5
1.0
Efficiency vs. Load Current 80
1.86 VIN = 10V
70 60
VIN = 5V VIN = 6V
SUPPLY CURRENT (mA)
1.84
EFFICIENCY (%)
1.82
50 40 30 20 10 VIN = 10V
1.80
1.78
1.76 -50
0 -25 0 25 50 75 100 1 2 3 4 5 6 7 8 9 10 TEMPERATURE (C) LOAD CURRENT (mA)
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TELCOM SEMICONDUCTOR, INC.
REGULATED GaAs FET BIAS SUPPLY
TCM850 TCM851 TCM852 TCM853
1
TYPICAL CHARACTERISTICS (Cont.)
Start-Up Time vs. Input Voltage 2.00 IOUT = 5mA
2 3
START-UP TIME (msec)
1.50
1.00
0.50
.00 5 6 7 8 9 10 INPUT VOLTAGE (V)
4 5 6 7
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