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19-0238; Rev 2; 4/96
Low-Noise, Regulated, Negative Charge-Pump Power Supplies for GaAsFET Bias
_______________General Description
The MAX850-MAX853 low-noise, inverting, chargepump 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 1A max over temperature (5A max for MAX851).
UAL IT MAN TION K T VALUA A SHEE E T WS DA FOLLO
____________________________Features
o Fixed -4.1V or Adjustable -0.5V to -9V Output at 5mA o 4.5V to 10V Input Voltage Range o 2mVp-p Output Voltage Ripple (MAX850-MAX852) 1mVp-p Output Voltage Ripple (MAX853) o 100kHz Charge-Pump Switching Frequency (MAX850/MAX851/MAX853) o External Synchronizing Clock Input (MAX852) o Logic-Level Shutdown Mode: 1A Max Over Temperature (MAX850/MAX852/MAX853) o Low Cost, 8-Pin SO Package
MAX850-MAX853
______________Ordering Information ________________________Applications
Cellular Phones Negative Regulated Power Supplies Personal Communicators, PDAs Wireless Data Loggers Continuously Adjustable GaAsFET Bias LCD-Bias Contrast Control
PART MAX850C/D MAX850ISA MAX850ESA MAX851C/D MAX851ISA MAX851ESA MAX852C/D TEMP. RANGE 0C to +70C -25C to +85C -40C to +850C 0C to +70C -25C to +85C -40C to +85C 0C to +70C PIN-PACKAGE Dice* 8 SO 8 SO Dice* 8 SO 8 SO Dice* 8 SO 8 SO Dice* 8 SO 8 SO
__________Typical Operating Circuit
VIN = 4.5V to 10.0V (4 CELLS)
MAX852ISA -25C to +85C MAX852ESA -40C to +85C MAX853C/D 0C to +70C MAX853ISA -25C to +85C MAX853ESA -40C to +85C * Dice are specified at TA = +25C only.
ise*
C3 IN C1+ C1 C1VOUT = -4.1V (VGG of GaAsFET) OUT C4
__________________Pin Configuration
TOP VIEW
MAX850 MAX851 MAX852
NEGOUT C2 SHDN* SHDN OSC GND * MAX850: SHDN MAX851: SHDN MAX852: OSC
C1+ 1 C1- 2 NEGOUT 3
8
IN GND OUT FB** (MAX850-852)
FB
SHDN* 4 (MAX850/853)
MAX850 MAX851 MAX852 MAX853
SO
7 6 5
* SHDN (MAX851) OSC (MAX852)
** CONT (MAX853)
________________________________________________________________ Maxim Integrated Products
1
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Low-Noise, Regulated, Negative Charge-Pump Power Supplies for GaAsFET Bias MAX850-MAX853
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VIN to GND ..................................-0.3V to 10.5V VNEGOUT to GND ...................................................-10.5V to 0.3V VIN to VNEGOUT .........................................................-0.3V 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 = +70C) SO (derate 5.88mW/C above +70C) ........................471mW Operating Temperature Ranges MAX85_ISA ......................................................-25C to +85C MAX85_ESA.....................................................-40C to +85C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10sec) .............................+300C
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.
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.
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.) PARAMETER Supply Voltage Range (Note 2) SYMBOL VIN MAX850-MAX852, VFB = 0V, RL = or 820, Figure 2a MAX853, VCTRL = 4.1V, RL = or 820, Figure 2c CONDITIONS MIN 5 -4.3 -4.2 -0.5 to -(VIN - 1) VFBset IQ MAX850/MAX853, VIN = 10V, SHDN = 0V Shutdown Supply Current ISHUT MAX851, SHDN = 2V MAX852, OSC low MAX850-MAX852, VFB = 0V, RL = or 820, Figure 2a VOUT Load Regulation MAX853, VCTRL = 4.1V, RL = or 820, Figure 2c VOUT Ripple Oscillator Frequency (Note 3) Input High Voltage Input Low Voltage Input Current Input Capacitance fOSC VIH VIL IIN CIN MAX850-MAX852 MAX853 MAX850/MAX851/MAX853, TA = +25C Pin 4 Pin 4 Pin 4 Pin 4 10 80 2.0 0.5 1 3 2 1 100 120 8 4 MAX850-MAX852, no load, Figure 2b -1.32 -1.28 2.0 0.002 2 -1.24 3.0 1 5 1 8 mV/mA A -4.1 TYP MAX 10 -3.9 V -4.0 V V mA UNITS V
Output Voltage
VOUT
Output Voltage Range Set Voltage Supply Current
mVp-p kHz V V A pF
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. 2 _____________________________________________________________________________________
Low-Noise, Regulated, Negative Charge-Pump Power Supplies for GaAsFET Bias
__________________________________________Typical Operating Characteristics
(Circuit of Figure 2a, VIN = 6V, TA = +25C, unless otherwise noted.)
MAX850-MAX853
OUTPUT VOLTAGE vs. OUTPUT CURRENT
MAX850-TOC1
OUTPUT VOLTAGE vs. INPUT VOLTAGE OVER TEMPERATURE
MAX850-TOC2
MAXIMUM OUTPUT CURRENT vs. INPUT VOLTAGE
MAXIMUM OUTPUT CURRENT (mA)
MAX850-TOC3
-4.16 -4.15 OUTPUT VOLTAGE (V) -4.14 -4.13 -4.12 -4.11 -4.10 0 2.0 4.0 6.0 8.0
-4.13 IOUT = 2.5mA -4.12 OUTPUT VOLTAGE (V) -4.11 -4.10 -4.09 TA = +85C -4.08 -4.07 -4.06 TA = +25C TA = -40C
60 50 40 30 20 10
10.0
5.0
6.0
7.0
8.0
9.0
10.0
5.0
6.0
7.0
8.0
9.0
10.0
OUTPUT CURRENT (mA)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
NO-LOAD SUPPLY CURRENT vs. INPUT VOLTAGE
MAX850-TOC4
SUPPLY CURRENT vs. TEMPERATURE
MAX850-TOC5
START-UP TIME vs. INPUT VOLTAGE
1.80 1.60 START-UP TIME (ms) 1.40 1.20 1.00 0.80 0.60 0.40 0.20 IOUT = 5mA
MAX850-TOC6
2.00 NO-LOAD SUPPLY CURRENT (mA) 1.80 1.60 1.40 1.20 1.00 0.80 0.60 5.0 6.0 7.0 8.0 9.0
2.5 2.4 SUPPLY CURRENT (mA) 2.3 2.2 2.1 2.0 1.9 1.8 1.7 1.6 VIN = 10.0V
2.00
10.0
-40
-20
0
20
40
60
80
100
5.0
6.0
7.0
8.0
9.0
10.0
INPUT VOLTAGE (V)
TEMPERATURE (C)
INPUT VOLTAGE (V)
EFFICIENCY vs. LOAD CURRENT
VIN = 5.0V 70 60 50 40 30 20 10 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 LOAD CURRENT (mA) VIN = 10.0V VIN = 6.0V
MAX850-TOC7
80
_______________________________________________________________________________________
EFFICIENCY (%)
3
Low-Noise, Regulated, Negative Charge-Pump Power Supplies for GaAsFET Bias MAX850-MAX853
_____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, VIN = 6V, TA = +25C, unless otherwise noted.) MAX850-MAX852 OUTPUT NOISE AND RIPPLE MAX853 OUTPUT NOISE AND RIPPLE
VOUT 500V/div
VOUT 500V/div
10s/div VIN = 6.0V, VOUT = -4.1V, IOUT = 5mA, AC COUPLED
10s/div VIN = 6.0V, VOUT = -4.1V, IOUT = 5mA, AC COUPLED
MAX850-MAX852 NOISE SPECTRUM
70 60 50 NOISE (dBV) NOISE (dBV) 40 30 20 10 0 -10 -20 -30 0.1 1.0 10 FREQUENCY (kHz) 100 1000 70 60 50 40 30 20 10 0 -10 -20 -30 0.1 1.0
MAX853 NOISE SPECTRUM
10 FREQUENCY (kHz)
100
1000
NOTE: dBV = 20 log VOUT 1V
4
______________________________________________________________________________________
Low-Noise, Regulated, Negative Charge-Pump Power Supplies for GaAsFET Bias
_____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, VIN = 6V, TA = +25C, unless otherwise noted.) MAX850/MAX851/MAX853 START-UP FROM SHUTDOWN MAX852 START-UP FROM SHUTDOWN
MAX850-MAX853
VOUT 2V/div
VOUT 2V/div
VSHDN 5V/div
VOSC 5V/div
200s/div CIRCUIT OF FIGURE 2a, VIN = 6.0V, VOUT = -4.1V, IOUT = 5mA
200s/div CIRCUIT OF FIGURE 2a, VIN = 6.0V, VOUT = -4.1V, IOUT = 5mA SHUTDOWN OCCURS WHEN 100kHz EXTERNAL CLOCK IS GATED OFF
LINE-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
0.01mA VOUT 20mV/div IOUT 5mA
6.0V V IN 5.5V
VOUT 50mV/div
2ms/div VOUT = -4.08V, IOUT = 5mA, AC COUPLED
1ms/div VOUT = -4.0V, AC COUPLED
_______________________________________________________________________________________
5
Low-Noise, Regulated, Negative Charge-Pump Power Supplies for GaAsFET Bias MAX850-MAX853
______________________________________________________________Pin Description
PIN
MAX850 1 2 3 4 - - 5 MAX851 1 2 3 - 4 - 5 MAX852 1 2 3 - - 4 5 MAX853 1 2 3 4 - - -
NAME
C1+ C1NEGOUT SHDN SHDN OSC FB Positive terminal for C1 Negative terminal for C1
FUNCTION
Negative Output Voltage (unregulated), VNEGOUT = VIN + 0.2V Active-low TTL logic level Shutdown Input Active-high TTL logic level Shutdown Input External Clock Input 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. Control Voltage Input. To set VOUT, connect a resistor divider between OUT and a positive control voltage between 0V and 10V. See Figure 2c. Output Voltage Ground Positive Power-Supply Input (4.5V to 10V)
- 6 7 8
- 6 7 8
- 6 7 8
5 6 7 8
CONT OUT GND IN
_______________Detailed Description
The MAX850-MAX853 are low-noise, inverting, regulated 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 minimum (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 addition, the excellent AC rejection of the linear regulator attenuates noise on the incoming supply. Up to 5mA is available at OUT.
C1+ C1CHARGE PUMP
IN C1+ IN CHARGE PUMP
NEGOUT
MAX850 MAX851 MAX852
N
C1OUT NEGOUT
MAX853
N OUT
SHDN (MAX850) SHDN (MAX851) OSC (MAX852)
FB CONNECT TO GND TO SET VOUT = -4.1V -1.28V REF SHDN
CONT CONTROL VOLTAGE
GND
GND
Figure 1a. MAX850-MAX852 Block Diagram
6
Figure 1b. MAX853 Block Diagram
______________________________________________________________________________________
Low-Noise, Regulated, Negative Charge-Pump Power Supplies for GaAsFET Bias
__________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 alternate output voltage, connect FB to the midpoint of a resistor 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 formula below. Choose R2 to be between 100k to 400k. R2 VOUT = -1.28 1 + R1
C1 1F C1+ IN
MAX850-MAX853
VIN C3 1F VOUT = -0.5V to -9V @ 5mA C1C2 1F
MAX853
OUT R2 100k CONT C4 10F
NEGOUT
SHDN GND
(
)
R1 100k VCTRL (0V TO 10V)
VIN
Figure 2c. MAX853 Standard Application Circuit
IN C1 1F C1+ C3 1F VOUT = -4.1V (VGG of GaAsFET) OUT C4 10F
C1-
MAX850 MAX851 MAX852
For the MAX853, set the output voltage, VOUT, by connecting a resistor voltage divider between OUT and a positive control voltage, VCTRL (Figure 2c.) R2 VOUT = - VCTRL R1
C2 1F
NEGOUT
Shutdown
SHDN* SHDN OSC GND *MAX850: SHDN MAX851: SHDN MAX852: OSC
FB
The MAX850-MAX853 feature a shutdown mode that reduces the supply current to 1A max over temperature (5A 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.
Figure 2a. MAX850/MAX851/MAX852 Standard Application Circuit
VIN C3 1F VOUT = (-1.28V) 1+ R2 R1
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 frequency, 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. 1F, 0.8 ESR capacitors are recommended for C1, C2, and C3. C4 should be 10F, 0.2 ESR. All capacitors should be either surface-mount chip tantalum or chip ceramic types. External capacitor values may be adjusted to optimize size and cost.
IN C1 1F C1+
C1-
MAX850 MAX851 MAX852
OUT
(
)
C2 1F
NEGOUT
C4 10F R2 100k
SHDN* SHDN OSC GND *MAX850: SHDN MAX851: SHDN MAX852: OSC
FB R1 100k
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
7
Figure 2b. MAX850/MAX851/MAX852 Adjustable Configuration
_______________________________________________________________________________________
Low-Noise, Regulated, Negative Charge-Pump Power Supplies for GaAsFET Bias MAX850-MAX853
sensitivity and interference. The clock must be a square wave between 40% and 60% duty cycle. The maximum clock frequency is 250kHz, and the minimum frequency is 50kHz.
___________________Chip Topography
C1+ IN
Layout and Grounding
Good layout is important, primarily for good noise performance. 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.
C1-
GND
0.127" (3.226mm)
NEGOUT
Noise and Ripple Measurement
Accurately measuring the output noise and ripple is a challenge. 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 capacitor (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 ripple measurement.
OUT
FB (MAX850-852) CONT (MAX853) SHDN (MAX850/853) SHDN (MAX851) OSC (MAX852) 0.085" (2.159mm)
TRANSISTOR COUNT: 164 SUBSTRATE CONNECTED TO IN
________________________________________________________Package Information
DIM A A1 B C D E e H h L INCHES MAX MIN 0.069 0.053 0.010 0.004 0.019 0.014 0.010 0.007 0.197 0.189 0.157 0.150 0.050 BSC 0.244 0.228 0.020 0.010 0.050 0.016 8 0 MILLIMETERS MIN MAX 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 4.80 5.00 3.80 4.00 1.27 BSC 5.80 6.20 0.25 0.50 0.40 1.27 0 8
21-325A
E
H
D A e B
0.127mm 0.004in.
h x 45
A1
C
L
8-PIN PLASTIC SMALL-OUTLINE PACKAGE
8
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