Document Outline
- Return to Contents
- List of Figures
- 1.
- 2.
- 3. TCM850/851/852 Standard Application
- 4. TCM850/851/852 Adjustable Application
- 5. TCM853 Standard Application Circuit
- Features
- Applications
- Functional Block Diagram
- General Description
- Ordering Information
- Absolute Maximum Ratings
- Electrical Characteristics: VIN between +5V and +10V; VOUT = 4.1V; RL = Open Circuit; TA = TMIN to TMAX unless otherwise noted
- Pin Configurations
- Pin Description
- Detailed Device Description
- Applications Information
- Setting the Output Voltage
- Shutdown Mode
- Charge Pump Frequency Control
- Capacitors
- Board Layout
- Noise and Ripple Measurement
- Evaluation Kit
- Typical Characteristics
4-27
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
REGULATED GaAs FET BIAS SUPPLY
TCM850
TCM851
TCM852
TCM853
FEATURES
s
Fixed 4.1V or Adjustable 0.5V to 9V Output
at 5mA
s
4.5V to 10V Input Voltage Range
s
Low Output Voltage Ripple
TCM850-852 .............................................. 2mVp-p
TCM853 ...................................................... 1mVp-p
s
100kHz Charge Pump Switching Frequency
s
Optional External Synchronizing Clock
Input (TCM852)
s
Logic Level Shutdown Mode ................ 0.5
A Typ.
Temperature (TCM850/852/853)
s
Low Cost, 8-Pin SOIC Package
APPLICATIONS
s
Cellular Phones
s
Negative Regulated Power Supplies
s
LCD Bias Contrast Control
s
Adjustable GaAs FET Bias
s
Wireless Data Loggers
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
0.5
A (typ) over temperature, 2
A (typ) for the TCM851.
CHARGE
PUMP
GND
N
FB
(GND to SET
V
OUT
= 4.1V)
OUT
NEGOUT
SHDN (TCM850)
SHDN (TCM851)
OSC (TCM852)
IN
TCM850
TCM851
TCM852
+
1.28V
REF
CHARGE
PUMP
GND
CONT
(CONTROL VOLTAGE)
OUT
NEGOUT
SHDN
IN
TCM853
+
N
C
1
C
1
C
2
C
3
C
2
C
4
C
4
C
3
C
1
+
C
1
C
1
+
C
1
ORDERING INFORMATION
Part No.
Package
Temp. Range
TCM850COA
8-Pin SOIC
0
C to +70
C
TCM850EOA
8-Pin SOIC
40
C to +85
C
TCM851COA
8-Pin SOIC
0
C to +70
C
TCM851EOA
8-Pin SOIC
40
C to +85
C
TCM852COA
8-Pin SOIC
0
C to +70
C
TCM852EOA
8-Pin SOIC
40
C to +85
C
TCM853COA
8-Pin SOIC
0
C to +70
C
TCM853EOA
8-Pin SOIC
40
C to +85
C
TCM850EV
Evaluation Kit for
TCM850/1/2/3
FUNCTIONAL BLOCK DIAGRAM
TC850/1/2/3-3 10/1/96
Figure 1.
EVALUATION
KIT
AVAILABLE
4-28
TELCOM SEMICONDUCTOR, INC.
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (V
IN
to GND) .................. 0.3V to +10.5V
V
NEGOUT
to GND ...................................... 10.5V to 0.3V
V
IN
to V
NEGOUT ...............................................................
0.3 to 21V
V
OUT
to GND** ........................................ V
NEGOUT
to 0.3V
SHDN or OSC (Pin 4) to GND ........ 0.3V to (V
IN
+ 0.3V)
Power Dissipation (T
A
< 70
C)
SOIC ........................................................... 470mW
Operating Temperature Range
C Device .............................................. 0
C to 70
C
E Device ....................................... 40
C to +85
C
Storage Temperature Range ................ 65
C to +165
C
Lead Temperature (Soldering, 10 sec) ................. +300
C
*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:
V
IN
between +5V and +10V; V
OUT
= 4.1V; R
L
= Open Circuit; T
A
= T
MIN
to
T
MAX
unless otherwise noted. A 100kHz, 50% duty cycle square wave
between GND and V
IN
is applied to the OSC pin of the TCM852.
Symbol
Parameter
Test Conditions
Min
Typ
Max
Unit
V
IN
Supply Voltage
Note 1
5
--
10
V
V
OUT
Output Voltage
TCM850-TCM852: V
FB
= 0V (Note 3)
4.3
4.1
3.9
V
TCM853: V
CTRL
= 4.1V
4.2
--
4
Output Voltage Range
0.5 to (V
IN
1)
V
V
FBSET
Set Voltage
TCM850-852: No Load
1.32
1.28
1.24
V
I
Q
Supply Current
--
2
3
mA
I
SHUT
Shutdown Supply Current
TCM850/853: V
IN
= 10V, SHDN = 0V
--
0.5
--
A
TCM851: SHDN = 2V
--
2
--
TCM852: OSC Low
--
0.5
--
V
OUT
Load Regulation
TCM850-TCM852: V
FB
= 0V (Note 3)
--
4
8
mV/mA
TCM853: V
CTRL
= 4.1V
--
3
8
V
OUT
Ripple
TCM850-TCM852
--
2
--
mVp-p
TCM853
--
1
--
f
OSC
Oscillator Frequency
TCM850-TCM853: T
A
= 25
C (Note 2)
80
100
120
kHz
V
IH
Input High Voltage
Pin 4
2
--
--
V
V
IL
Input Low Voltage
Pin 4
--
--
0.5
V
I
IN
Input Current
Pin 4
--
--
1
A
C
IN
Input Capacitance
Pin 4
--
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. I
OUT
= 0mA or 5mA. Reference Figures 3 and 5.
REGULATED GaAs FET BIAS SUPPLY
TCM850
TCM851
TCM852
TCM853
4-29
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
PIN CONFIGURATIONS
SHDN
C1+
C1
NEGOUT
IN
OUT
GND
FB
TCM850COA
TCM850EOA
SHDN
C1+
C1
NEGOUT
IN
OUT
GND
FB
TCM851COA
TCM851EOA
OSC
C1+
C1
NEGOUT
IN
OUT
GND
FB
TCM852COA
TCM852EOA
SHDN
C1+
C1
NEGOUT
IN
OUT
GND
CONT
TCM853COA
TCM853EOA
1
2
3
4
8
7
6
5
1
2
3
4
8
7
6
5
1
2
3
4
8
7
6
5
1
2
3
4
8
7
6
5
PIN DESCRIPTION
Pin No
Pin No
Pin No
Pin No
(TCM850)
(TCM851)
(TCM852)
(TCM853)
Symbol
Description
1
1
1
1
C
1
+
C1 positive input terminal.
2
2
2
2
C
1
C1 negative input terminal.
3
3
3
3
NEGOUT
Negative (unregulated) output voltage.
4
--
--
4
SHDN
Shutdown input (TTL active LOW).
--
4
--
--
SHDN
Shutdown input (TTL active HIGH).
--
--
4
--
OSC
External oscillator input.
5
5
5
--
FB
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.
--
--
--
5
CONT
Control input. V
OUT
is adjusted with a positive control
voltage (0V to 10V) applied to this input through a resistive
divider (Figure 5).
6
6
6
6
OUT
Output voltage terminal.
7
7
7
7
GND
Ground.
8
8
8
8
IN
Positive power supply input voltage (4.5V to 10V).
8-Pin SOIC
Figure 2.
REGULATED GaAs FET BIAS SUPPLY
TCM850
TCM851
TCM852
TCM853
4-30
TELCOM SEMICONDUCTOR, INC.
The relationship between output voltage and control
voltage for the TCM853 (Figure 5) is given by:
V
OUT
= V
CTRL
(1.28)
(
R2
R1
)
Figure 4. TCM850/851/852 Adjustable Application
NEGOUT
FB
OUT
V
IN
All caps = 1.0
F unless otherwise noted
TCM850
TCM851
TCM852
C
1
C
3
C
2
GND
C
1
+
C
1
SHDN
SHDN
OSC
V
OUT
= 2.56V
R2 = 100k
R1 = 100k
I
OUT
C
4
10
F
Figure 5. TCM853 Standard Application Circuit
DETAILED DEVICE DESCRIPTION
The voltage applied to V
IN
is inverted by a capacitive
charge pump (using commutating capacitor C1 and reser-
voir 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.
V
IN
) 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.
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
):
V
OUT
= (1.28)
(
1+
R2
R1
)
NEGOUT
FB
OUT
V
IN
V
OUT
= 4.1V
All caps = 1.0
F unless otherwise noted
I
OUT
TCM850
TCM851
TCM852
C
1
C
3
C
2
C
4
10
F
GND
C
1
+
C
1
SHDN
SHDN
OSC
Figure 3. TCM850/851/852 Standard Application
NEGOUT
CONT
OUT
V
IN
V
OUT
= 0.5V to 9.0V
VCTRL (0 to 10V)
All caps = 1.0
F unless otherwise noted
R2 = 100k
R1 = 100k
I
OUT
TCM853
C
1
C
3
C
2
C
4
10
F
GND
C
1
+
C
1
SHDN
TCM850
TCM851
TCM852
TCM853
REGULATED GaAs FET BIAS SUPPLY
4-31
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
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 0.5
A (typ) TCM850/2/3 and 2
A (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.
Charge Pump Frequency Control
In applications where the charge pump switching fre-
quency 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.
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 1
F, 0.8
ESR. The recommended value for C4 is
10
F, 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.
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.
Evaluation Kit
TelCom Semiconductor offers evaluation kit
(TCM850EV) for the TCM850-853. A second evaluation kit
(TC7660EV) evaluates several TelCom charge pumps in-
cluding the TC7660, TC7660S, TC7662B, TC962, TC682.
This kit also supports the TCM850 (but not the TCM851-
853).
4-32
TELCOM SEMICONDUCTOR, INC.
TYPICAL CHARACTERISTICS
INPUT VOLTAGE (V)
5
6
7
8
9
10
Output Voltage vs. Input Voltage Over Temperature
OUTPUT CURRENT (mA)
4.06
4.07
4.08
4.09
4.11
4.10
0
2
1
4
3
6
5
8
7
10
9
SUPPLY VOLTAGE
4.06
4.07
4.08
4.09
4.11
4.10
OUTPUT VOLTAGE
Output Voltage vs. Output Current
V
IN
= 6V
I
OUT
= 3mA
T
A
= 40
C
T
A
= 85
C
T
A
= 25
C
INPUT VOLTAGE (V)
2.0
1.5
1.0
0.5
5
6
8
9
7
10
SUPPLY CURRENT (mA)
No-Load Supply Current vs. Input Voltage
INPUT VOLTAGE (V)
80
70
60
50
30
20
10
0
40
5.0
6.0
5.5
7.0
6.5
8.0
7.5
9.0
8.5
10.0
9.5
MAXIMUM OUTPUT CURRENT (mA)
Maximum Output Current vs. Input Voltage
LOAD CURRENT (mA)
80
70
60
50
30
20
10
0
40
1
3
2
5
4
7
6
9
10
8
EFFICIENCY (%)
Efficiency vs. Load Current
TEMPERATURE (
C)
50
-25
0
25
50
75
100
Supply Current vs. Temperature
1.86
1.84
1.82
1.80
1.76
1.78
SUPPLY CURRENT (mA)
V
IN
= 10V
V
IN
= 5V
V
IN
= 6V
V
IN
= 10V
REGULATED GaAs FET BIAS SUPPLY
TCM850
TCM851
TCM852
TCM853
4-33
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
TYPICAL CHARACTERISTICS (Cont.)
2.00
1.50
0.50
1.00
.00
5
6
7
8
9
10
START-UP TIME (msec)
Start-Up Time vs. Input Voltage
I
OUT
= 5mA
INPUT VOLTAGE (V)
REGULATED GaAs FET BIAS SUPPLY
TCM850
TCM851
TCM852
TCM853
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