_______________general description the max850?ax853 low-noise, inverting, charge- pump power supplies are ideal for biasing gaasfets in cellular telephone transmitter amplifiers. the max850?ax852 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 (v ctrl ), the MAX853 achieves typical output ripple of less than 1mvp-p. supply current is 3ma max, and shutdown current is less than 1? max over temperature (5? 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?ax852) 1mvp-p output voltage ripple (MAX853) ? 100khz charge-pump switching frequency (max850/max851/MAX853) ? external synchronizing clock input (max852) ? logic-level shutdown mode: 1? 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?52) 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 v in = 4.5v to 10.0v
(4 cells) c3 v out = -4.1v
(v gg of gaasfet) c4 c1 c2 * max850: shdn
max851: shdn
max852: osc __________typical operating circuit 19-0238; rev 2; 4/96 part max850isa max850esa -40? to +850? -25? to +85? 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 max851 c/d 0? to +70? dice* max851isa -25? to +85? 8 so max851esa -40? to +85? 8 so max852 c/d max852isa max852esa -40? to +85? -25? to +85? 0? to +70? dice* 8 so ise* 8 so MAX853 c/d 0? to +70? dice* MAX853isa -25? to +85? 8 so MAX853esa -40? to +85? 8 so max850 c/d 0? to +70? dice* max850?ax853 evaluation kit manual follows data sheet
max850?ax853 low-noise, regulated, negative charge-pump power supplies for gaasfet bias 2 _____________________________________________________________________________________ absolute maximum ratings electrical characteristics (+5v v in +10v, gnd = 0v, v out = -4.1v, r l = , 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 osc on the max852.) stresses beyond those listed under ?bsolute 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, v in to gnd ..................................-0.3v to 10.5v v negout to gnd ...................................................-10.5v to 0.3v v in to v negout .........................................................-0.3v to 21v v out to gnd (note 1) ........................................v negout to 0.3v shdn or osc (pin 4) voltage to gnd.........-0.3v to (v in + 0.3v) continuous power dissipation (t a = +70?) so (derate 5.88mw/? above +70?) ........................471mw operating temperature ranges max85_isa ......................................................-25? to +85? max85_esa.....................................................-40? to +85? storage temperature range .............................-65? to +160? lead temperature (soldering, 10sec) .............................+300? pin 4 pin 4 pin 4 max850?ax852, v fb = 0v, r l = or 820 , figure 2a pin 4 max850/max851/MAX853, t a = +25? MAX853 max850?ax852 MAX853, v ctrl = 4.1v, r l = or 820 , figure 2c max850/MAX853, v in = 10v, shdn = 0v max850?ax852, v fb = 0v, r l = or 820 , figure 2a max850?ax852, no load, figure 2b MAX853, v ctrl = 4.1v, r l = or 820 , figure 2c max852, osc low max851, shdn = 2v conditions pf 10 c in input capacitance ? ? i in input current v 0.5 v il input low voltage v 2.0 v ih input high voltage khz 80 100 120 f osc oscillator frequency (note 3) mvp-p 1 v out ripple 2 mv/ma 38 v out load regulation 48 ? 1 i shut shutdown supply current 25 -4.3 -4.1 -3.9 v 510 v in supply voltage range (note 2) 0.002 1 ma 2.0 3.0 i q supply current v -1.32 -1.28 -1.24 v fbset set voltage v -0.5 to -(v in - 1) output voltage range v -4.2 -4.0 v out output voltage units min typ max symbol parameter
max850?ax853 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 -4.06 5.0 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 t a = +25? t a = -40? t a = +85? i out = 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 9.0 7.0 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 (?) supply current (ma) 06080 2.1 2.0 1.9 1.8 v in = 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 9.0 7.0 8.0 10.0 i out = 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 (%) v in = 6.0v v in = 5.0v v in = 10.0v __________________________________________typical operating characteristics (circuit of figure 2a, v in = 6v, t a = +25?, unless otherwise noted.)
max850?ax853 low-noise, regulated, negative charge-pump power supplies for gaasfet bias 4 ______________________________________________________________________________________ v in = 6.0v, v out = -4.1v, i out = 5ma, ac coupled max850?ax852
output noise and ripple v out
500 m v/div 10 m s/div _____________________________typical operating characteristics (continued) (circuit of figure 2a, v in = 6v, t a = +25?, unless otherwise noted.) v in = 6.0v, v out = -4.1v, i out = 5ma, ac coupled MAX853
output noise and ripple v out
500 m v/div 10 m s/div max850?ax852
noise spectrum 70 60 50 40 30 20 10 0 -10 -20 -30 noise (db m v) 0.1 1000 100 10 1.0 frequency (khz) MAX853
noise spectrum 70 60 50 40 30 20 10 0 -10 -20 -30 noise (db m v) 0.1 1000 100 10 1.0 frequency (khz) note: db? = 20 log v out 1?
max850?ax853 low-noise, regulated, negative charge-pump power supplies for gaasfet bias _______________________________________________________________________________________ 5 _____________________________typical operating characteristics (continued) (circuit of figure 2a, v in = 6v, t a = +25?, unless otherwise noted.) circuit of figure 2a, v in = 6.0v, v out = -4.1v, i out = 5ma max850/max851/MAX853
start-up from shutdown v out
2v/div v shdn
5v/div 200 m s/div circuit of figure 2a, v in = 6.0v, v out = -4.1v, i out = 5ma
shutdown occurs when 100khz external clock is gated off max852
start-up from shutdown v out
2v/div v osc
5v/div
200 m s/div v out = -4.08v, i out = 5ma, ac coupled
line-transient response v out
20mv/div v in
6.0v
5.5v 2ms/div v out = -4.0v, ac coupled
load-transient response i out 0.01 ma 5 ma v out
50mv/div 1ms/div
max850?ax853 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
v out = -4.1v fb gnd MAX853 charge
pump in n c1+ c1- negout shdn
out control
voltage cont gnd _______________detailed description the max850?ax853 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 (v in ) 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 (v out ) 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 v out for the max850?ax852. 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?ax852 block diagram figure 1b. MAX853 block diagram max850 1 max851 1 MAX853 1 pin max852 1 name c1+ function positive terminal for c1 3 2 3 3 4 2 3 2 4 negout shdn 2 c1- negative output voltage (unregulated), v negout = v in + 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 5 5 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 v out , 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 8 gnd in 6 out ground positive power-supply input (4.5v to 10v) output voltage
max850?ax853 low-noise, regulated, negative charge-pump power supplies for gaasfet bias _______________________________________________________________________________________ 7 __________applications information setting the output voltage for the max850?ax852, 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). v in must be 1.0v above the absolute value of v out to allow proper regulation. the output voltage is calculated from the formu- la below. choose r2 to be between 100k to 400k . for the MAX853, set the output voltage, vout, by con- necting a resistor voltage divider between out and a positive control voltage, v ctrl (figure 2c.) shutdown the max850?ax853 feature a shutdown mode that reduces the supply current to 1? max over temperature (5? 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 (v in - | v out | ). the overall dropout voltage is a function of the charge pump? 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? esr. therefore, minimizing the esr of the charge-pump capacitors minimizes the dropout voltage. 1?, 0.8 esr capacitors are recommended for c1, c2, and c3. c4 should be 10?, 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. 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 v in c3
1 m f v out = -4.1v
(v gg of gaasfet) *max850: shdn
max851: shdn
max852: osc c4
10 m f c1
1 m f c2
1 m f MAX853 cont out shdn negout c1- c1+ in gnd v in c3
1 m f v out = -0.5v to -9v @ 5ma c4
10 m f c1
1 m f c2
1 m f r2
100k r1
100k v ctrl (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 v in c3
1 m f v out = (-1.28v) 1+ r2
r1 *max850: shdn
max851: shdn
max852: osc c4
10 m f c1
1 m f c2
1 m f r2
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?ax853 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?ax853 circuit and the oscilloscope (which result from the charge pump? switching action) cause ground currents in the probe? 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? tip cover and touch the ground ring on the probe directly to c4? 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?52)
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
a 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 a 8-pin plastic
small-outline
package h e d e a a1 c h x 45? 0.127mm
0.004in. b 1.27 bsc 0.050 bsc 21-325a
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