_______________General Description
The MAX850–MAX853 low-noise, inverting, charge-
pump power supplies are ideal for biasing GaAsFETs in
cellular telephone transmitter amplifiers.
The MAX850–MAX852 offer both preset (-4.1V) and
adjustable (-0.5V to -9.0V) output voltages. The
MAX853 uses an external positive control voltage to set
the negative output voltage. Input voltage range for all
four devices is 4.5V to 10V. Output current is 5mA.
An internal linear regulator reduces the output voltage
ripple to 2mVp-p. With a well-filtered control voltage
(VCTRL), the MAX853 achieves typical output ripple of
less than 1mVp-p. Supply current is 3mA max, and
shutdown current is less than 1µA max over temperature
(5µA max for MAX851).
________________________Applications
Cellular Phones
Negative Regulated Power Supplies
Personal Communicators, PDAs
Wireless Data Loggers
Continuously Adjustable GaAsFET Bias
LCD-Bias Contrast Control
____________________________Features
♦Fixed -4.1V or Adjustable -0.5V to -9V Output at 5mA
♦4.5V to 10V Input Voltage Range
♦2mVp-p Output Voltage Ripple (MAX850–MAX852)
1mVp-p Output Voltage Ripple (MAX853)
♦100kHz Charge-Pump Switching Frequency
(MAX850/MAX851/MAX853)
♦External Synchronizing Clock Input (MAX852)
♦Logic-Level Shutdown Mode: 1µA Max Over
Temperature (MAX850/MAX852/MAX853)
♦Low Cost, 8-Pin SO Package
Low-Noise, Regulated, Negative
Charge-Pump Power Supplies for GaAsFET Bias
________________________________________________________________
Maxim Integrated Products
1
1
2
3
4
8
7
6
5
IN
GND
OUT
FB**
(MAX850–852)
SHDN*
(MAX850/853)
NEGOUT
C1-
C1+
MAX850
MAX851
MAX852
MAX853
SO
TOP VIEW
* SHDN (MAX851)
OSC (MAX852) ** CONT (MAX853)
__________________Pin Configuration
MAX850
MAX851
MAX852
FB
OUT
SHDN*
SHDN
OSC
NEGOUT
C1-
C1+ IN
GND
VIN = 4.5V to 10.0V
(4 CELLS)
C3
VOUT = -4.1V
(VGG of GaAsFET)
C4
C1
C2
* MAX850: SHDN
MAX851: SHDN
MAX852: OSC
__________Typical Operating Circuit
19-0238; Rev 2; 4/96
PART
MAX850ISA
MAX850ESA -40°C to +850°C
-25°C to +85°C
TEMP. RANGE PIN-PACKAGE
8 SO
8 SO
______________Ordering Information
* Dice are specified at T
A
= +25 °C only.
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAX851C/D 0°C to +70°C Dice*
MAX851ISA -25°C to +85°C 8 SO
MAX851ESA -40°C to +85°C 8 SO
MAX852C/D
MAX852ISA
MAX852ESA -40°C to +85°C
-25°C to +85°C
0°C to +70°C Dice*
8 SO
ise* 8 SO
MAX853C/D 0°C to +70°C Dice*
MAX853ISA -25°C to +85°C 8 SO
MAX853ESA -40°C to +85°C 8 SO
MAX850C/D 0°C to +70°C Dice*
MAX850–MAX853
EVALUATION KIT MANUAL
FOLLOWS DATA SHEET
MAX850–MAX853
Low-Noise, Regulated, Negative
Charge-Pump Power Supplies for GaAsFET Bias
2 _____________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(+5V ≤VIN ≤+10V, GND = 0V, VOUT = -4.1V, RL= ∞, TA= TMIN to TMAX, unless otherwise noted. A 100kHz, 50% duty cycle square
wave between GND and VIN is applied to OSC on the MAX852.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond 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.
Note 1: 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.
Note 2: The supply voltage can drop to 4.5V, but the output may no longer sink 5mA at -4.1V.
Note 3: The MAX852 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.
Supply Voltage, VIN to GND..................................-0.3V to 10.5V
VNEGOUT to GND...................................................-10.5V to 0.3V
VIN to VNEGOUT .........................................................-0.3V to 21V
VOUT to GND (Note 1)........................................VNEGOUT to 0.3V
SHDN or OSC (pin 4) Voltage to GND.........-0.3V to (VIN + 0.3V)
Continuous Power Dissipation (TA= +70°C)
SO (derate 5.88mW/°C above +70°C) ........................471mW
Operating Temperature Ranges
MAX85_ISA......................................................-25°C to +85°C
MAX85_ESA.....................................................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
Pin 4
Pin 4
Pin 4
MAX850–MAX852, VFB = 0V,
RL= ∞or 820Ω, Figure 2a
Pin 4
MAX850/MAX851/MAX853, TA= +25°C
MAX853
MAX850–MAX852
MAX853, VCTRL = 4.1V,
RL= ∞or 820Ω, Figure 2c
MAX850/MAX853, VIN = 10V, SHDN = 0V
MAX850–MAX852, VFB = 0V,
RL= ∞or 820Ω, Figure 2a
MAX850–MAX852, no load, Figure 2b
MAX853, VCTRL = 4.1V,
RL= ∞or 820Ω, Figure 2c
MAX852, OSC low
MAX851, SHDN = 2V
CONDITIONS
pF10CIN
Input Capacitance
µA±1IIN
Input Current
V0.5VIL
Input Low Voltage
V2.0VIH
Input High Voltage
kHz80 100 120fOSC
Oscillator Frequency (Note 3)
mVp-p
1
VOUT Ripple 2
mV/mA
38
V
OUT Load Regulation
48
µA
1
ISHUT
Shutdown Supply Current 25
-4.3 -4.1 -3.9
V510V
IN
Supply Voltage Range (Note 2)
0.002 1
mA2.0 3.0IQ
Supply Current
V-1.32 -1.28 -1.24VFBset
Set Voltage
V-0.5 to -(VIN - 1)Output Voltage Range
V
-4.2 -4.0
VOUT
Output Voltage
UNITSMIN TYP MAXSYMBOLPARAMETER
MAX850–MAX853
Low-Noise, Regulated, Negative
Charge-Pump Power Supplies for GaAsFET Bias
_______________________________________________________________________________________
3
-4.10 0
OUTPUT VOLTAGE 
vs. OUTPUT CURRENT
MAX850-TOC1
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
-4.11
-4.14
-4.13
-4.12
-4.15
-4.16
2.0 4.0 6.0 8.0 10.0 -4.065.0
OUTPUT VOLTAGE vs.
INPUT VOLTAGE OVER TEMPERATURE
MAX850-TOC2
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
-4.07
-4.11
-4.10
-4.09
-4.08
-4.12
-4.13
-4.12
6.0 7.0 8.0 9.0 10.0
TA = +25°C
TA = -40°C
TA = +85°C
IOUT = 2.5mA
10
20
30
40
50
60
5.0 6.0 7.0 8.0 9.0 10.0
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
MAX850-TOC3
INPUT VOLTAGE (V)
MAXIMUM OUTPUT CURRENT (mA)
0.60
0.80
1.00
1.20
5.0 6.0
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX850-TOC4
INPUT VOLTAGE (V)
NO-LOAD SUPPLY CURRENT (mA)
1.40
1.60
1.80
2.00
9.07.0 8.0 10.0
2.5
1.6 -40 -20 20 40 100
SUPPLY CURRENT 
vs. TEMPERATURE
1.7
2.2
2.3
2.4
MAX850-TOC5
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
06080
2.1
2.0
1.9
1.8
VIN = 10.0V
0.20
0.40
0.60
0.80
5.0 6.0
START-UP TIME vs.
INPUT VOLTAGE
MAX850-TOC6
INPUT VOLTAGE (V)
START-UP TIME (ms)
1.00
1.20
1.40
1.60
1.80
2.00
9.07.0 8.0 10.0
IOUT = 5mA
10
20
30
50
60
40
70
80
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
EFFICIENCY vs. LOAD CURRENT
MAX850-TOC7
LOAD CURRENT (mA)
EFFICIENCY (%)
VIN = 6.0V
VIN = 5.0V
VIN = 10.0V
__________________________________________Typical Operating Characteristics
(Circuit of Figure 2a, VIN = 6V, TA = +25°C, unless otherwise noted.)
MAX850–MAX853
Low-Noise, Regulated, Negative
Charge-Pump Power Supplies for GaAsFET Bias
4 ______________________________________________________________________________________
VIN = 6.0V, VOUT = -4.1V, IOUT = 5mA, AC COUPLED
MAX850–MAX852
OUTPUT NOISE AND RIPPLE
VOUT
500µV/div
10µs/div
_____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, VIN = 6V, TA = +25°C, unless otherwise noted.)
VIN = 6.0V, VOUT = -4.1V, IOUT = 5mA, AC COUPLED
MAX853
OUTPUT NOISE AND RIPPLE
VOUT
500µV/div
10µs/div
MAX850–MAX852
NOISE SPECTRUM
70
60
50
40
30
20
10
0
-10
-20
-30
NOISE (dBµV)
0.1 1000100101.0 FREQUENCY (kHz)
MAX853
NOISE SPECTRUM
70
60
50
40
30
20
10
0
-10
-20
-30
NOISE (dBµV)
0.1 1000100101.0 FREQUENCY (kHz)
NOTE: dBµV = 20 log VOUT
1µV
MAX850–MAX853
Low-Noise, Regulated, Negative
Charge-Pump Power Supplies for GaAsFET Bias
_______________________________________________________________________________________ 5
_____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, VIN = 6V, TA = +25°C, unless otherwise noted.)
CIRCUIT OF FIGURE 2a, VIN = 6.0V, VOUT = -4.1V, IOUT = 5mA
MAX850/MAX851/MAX853
START-UP FROM SHUTDOWN
VOUT
2V/div
VSHDN
5V/div
200µs/div CIRCUIT OF FIGURE 2a, VIN = 6.0V, VOUT = -4.1V, IOUT = 5mA
SHUTDOWN OCCURS WHEN 100kHz EXTERNAL CLOCK IS GATED OFF
MAX852
START-UP FROM SHUTDOWN
VOUT
2V/div
VOSC
5V/div
200µs/div
VOUT = -4.08V, IOUT = 5mA, AC COUPLED
LINE-TRANSIENT RESPONSE
VOUT
20mV/div
VIN
6.0V
5.5V
2ms/div VOUT = -4.0V, AC COUPLED
LOAD-TRANSIENT RESPONSE
IOUT
0.01mA
5mA
VOUT
50mV/div
1ms/div
MAX850–MAX853
Low-Noise, Regulated, Negative
Charge-Pump Power Supplies for GaAsFET Bias
6 ______________________________________________________________________________________
______________________________________________________________Pin Description
MAX850
MAX851
MAX852
-1.28V
REF
CHARGE
PUMP
IN
N
C1+
C1-
NEGOUT
SHDN (MAX850)
SHDN (MAX851)
OSC (MAX852)
OUT
CONNECT TO 
GND TO SET
VOUT = -4.1V
FB
GND
MAX853
CHARGE
PUMP
IN
N
C1+
C1-
NEGOUT
SHDN
OUT
CONTROL
VOLTAGE
CONT
GND
_______________Detailed Description
The MAX850–MAX853 are low-noise, inverting, regulat-
ed charge-pump power supplies designed for biasing
GaAsFET devices, such as power-amplifier modules in
cellular handsets.
The applied input voltage (VIN) is first inverted to a
negative voltage at NEGOUT by a capacitive charge
pump. This voltage is then regulated by an internal lin-
ear regulator, and appears at OUT (Figure 1). The mini-
mum (most negative) output voltage (VOUT) achievable
is the inverted positive voltage, plus the 1.0V required
by the post-regulator. The ripple noise induced by the
charge-pump inverter is reduced by the linear regulator
to 2mVp-p at VOUT for the MAX850–MAX852. In addi-
tion, the excellent AC rejection of the linear regulator
attenuates noise on the incoming supply. Up to 5mA is
available at OUT.
Figure 1a. MAX850–MAX852 Block Diagram Figure 1b. MAX853 Block Diagram
MAX850
1MAX851
1MAX853
1
PIN
MAX852
1
NAME
C1+
FUNCTION
Positive terminal for C1
3
–
2
3 3
4
2
3
–
2
4NEGOUT
SHDN
2 C1- Negative Output Voltage (unregulated), VNEGOUT = VIN + 0.2V
Active-low TTL logic level Shutdown Input
Negative terminal for C1
–
4
– –
–
4
–OSC
– SHDN External Clock Input
Active-high TTL logic level Shutdown Input
55 –5 FB Dual-Mode Feedback Input. When FB is grounded, the output is preset to
-4.1V. To select other output voltages, connect FB to an external resistor
divider. See Figure 2b.
– 5–– CONT Control Voltage Input. To set VOUT, connect a resistor divider between
OUT and a positive control voltage between 0V and 10V. See Figure 2c.
7
8
6
7 7
8
6
7
8
6
8GND
IN
6 OUT Ground
Positive Power-Supply Input (4.5V to 10V)
Output Voltage
MAX850–MAX853
Low-Noise, Regulated, Negative
Charge-Pump Power Supplies for GaAsFET Bias
_______________________________________________________________________________________ 7
__________Applications Information
Setting the Output Voltage
For the MAX850–MAX852, select either a fixed or an
adjustable output voltage. Connect FB directly to GND to
select the fixed -4.1V output (Figure 2a). To select an alter-
nate output voltage, connect FB to the midpoint of a resis-
tor voltage divider from OUT to GND (Figure 2b). VIN must
be 1.0V above the absolute value of VOUT to allow proper
regulation. The output voltage is calculated from the formu-
la below. Choose R2 to be between 100kΩto 400kΩ.
For the MAX853, set the output voltage, VOUT, by con-
necting a resistor voltage divider between OUT and a
positive control voltage, VCTRL (Figure 2c.)
Shutdown
The MAX850–MAX853 feature a shutdown mode that
reduces the supply current to 1µA max over temperature
(5µA max for the MAX851). The MAX850 and MAX853 have
an active-low TTL logic level SHDN input, whereas the
MAX851 has an active-high SHDN input. To shut down the
MAX852, set the OCSC input to a logic-low level. The device
is powered up by the resumption of the clock signal.
Capacitors
Use capacitors with low effective series resistance (ESR) to
maintain a low dropout voltage (VIN - |VOUT|). The overall
dropout voltage is a function of the charge pump’s output
resistance and the voltage drop across the linear regulator
(N-channel pass transistor). At the 100kHz switching fre-
quency, the charge-pump output resistance is a function of
C1 and C2’s ESR. Therefore, minimizing the ESR of the
charge-pump capacitors minimizes the dropout voltage.
1µF, 0.8ΩESR capacitors are recommended for C1, C2,
and C3. C4 should be 10µF, 0.2ΩESR. All capacitors
should be either surface-mount chip tantalum or chip
ceramic types. External capacitor values may be adjusted to
optimize size and cost.
Switching-Frequency Control
Use the MAX852 to minimize system interference caused by
conflicting clock frequencies. An external oscillator can set
the charge-pump frequency and reduce clock frequency
MAX850
MAX851
MAX852
FB
OUT
SHDN*
SHDN
OSC
NEGOUT
C1-
C1+ IN
GND
VIN
C3
1µF
VOUT = -4.1V
(VGG of GaAsFET)
*MAX850: SHDN
MAX851: SHDN
MAX852: OSC
C4
10µF
C1
1µF
C2
1µF
MAX853
CONT
OUT
SHDN
NEGOUT
C1-
C1+ IN
GND
VIN
C3
1µF
VOUT = -0.5V to -9V @ 5mA
C4
10µF
C1
1µF
C2
1µFR2
100k
R1
100k
VCTRL (0V TO 10V)
Figure 2a. MAX850/MAX851/MAX852 Standard Application Circuit
Figure 2c. MAX853 Standard Application Circuit
MAX850
MAX851
MAX852
FB
OUT
SHDN*
SHDN
OSC
NEGOUT
C1-
C1+ IN
GND
VIN
C3
1µF
VOUT = (-1.28V) 1+R2
R1
*MAX850: SHDN
MAX851: SHDN
MAX852: OSC
C4
10µF
C1
1µF
C2
1µFR2
100k
R1
100k
( )
Figure 2b. MAX850/MAX851/MAX852 Adjustable Configuration
V = -1.28
OUT
()
+
1 2
1
R
R
V = -V R2
R1
OUT CTRL
MAX850–MAX853
Low-Noise, Regulated, Negative
Charge-Pump Power Supplies for GaAsFET Bias
8 ______________________________________________________________________________________
___________________Chip Topography
________________________________________________________Package Information
sensitivity and interference. The clock must be a square wave
between 40% and 60% duty cycle. The maximum clock fre-
quency is 250kHz, and the minimum frequency is 50kHz.
Layout and Grounding
Good layout is important, primarily for good noise perfor-
mance.
1) Mount all components as close together as possible.
2) Keep traces short to minimize parasitic inductance
and capacitance. This includes connections to FB.
3) Use a ground plane.
Noise and Ripple Measurement
Accurately measuring the output noise and ripple is a chal-
lenge. Brief differences in ground potential between the
MAX850–MAX853 circuit and the oscilloscope (which result
from the charge pump’s switching action) cause ground
currents in the probe’s wires, inducing sharp voltage spikes.
For best results, measure directly across the output capaci-
tor (C4). Do not use the ground lead of the oscilloscope
probe; instead, remove the probe’s tip cover and touch the
ground ring on the probe directly to C4’s ground terminal.
You can also use a Tektronix chassis mount test jack (part
no. 131-0258) to connect your scope probe directly. This
direct connection gives the most accurate noise and rip-
ple measurement.
FB (MAX850–852)
CONT (MAX853)
OUT
GND
IN
NEGOUT
C1-
C1+
SHDN (MAX850/853)
SHDN (MAX851)
OSC (MAX852)
0.127"
(3.226mm)
0.085"
(2.159mm)
TRANSISTOR COUNT: 164
SUBSTRATE CONNECTED TO IN
L
DIM
A
A1
B
C
D
E
e
H
h
L
α
MIN
0.053
0.004
0.014
0.007
0.189
0.150
0.228
0.010
0.016
0˚
MAX
0.069
0.010
0.019
0.010
0.197
0.157
0.244
0.020
0.050
8˚
MIN
1.35
0.10
0.35
0.19
4.80
3.80
5.80
0.25
0.40
0˚
MAX
1.75
0.25
0.49
0.25
5.00
4.00
6.20
0.50
1.27
8˚
INCHES MILLIMETERS
α
8-PIN PLASTIC
SMALL-OUTLINE
PACKAGE
HE
D
e
A
A1 C
h x 45˚
0.127mm
0.004in.
B
1.27 BSC0.050 BSC
21-325A