MAX865 [MAXIM]
Compact, Dual-Output Charge Pump; 紧凑型，双输出电荷泵
| 型号： | MAX865 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Compact, Dual-Output Charge Pump |
| 文件： | 总8页 (文件大小：91K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0472; Rev 1; 7/97
Co m p a c t , Du a l-Ou t p u t Ch a rg e P u m p
MAX865
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
♦ 1.11mm-High µMAX Package
♦ Compact: Circuit Fits in 0.08in2
The MAX865 is a CMOS charge-pump DC-DC convert-
er in an ultra-small µMAX package. It produces positive
and negative outputs from a single positive input, and
requires only four capacitors. The charge pump first
doubles the input voltage, then inverts the doubled volt-
age. The input voltage ranges from +1.5V to +6.0V.
♦ Requires Only Four Capacitors
♦ Dual Outputs (positive and negative)
♦ +1.5V to +6.0V Input Voltage
The internal oscillator is guaranteed to be between
20kHz a nd 38kHz, ke e p ing nois e a b ove the a ud io
range while consuming minimal supply current. A 75Ω
output impedance permits useful output currents up to
20mA.
♦ 20kHz (min) Frequency (above the audio range)
The MAX865 comes in a 1.11mm-high, 8-pin µMAX
package that occupies half the board area of a stan-
dard 8-pin SOIC. For a device with selectable frequen-
cies and logic-controlled shutdown, refer to the MAX864
data sheet.
______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
Dice
________________________Ap p lic a t io n s
Low-Voltage GaAsFET Bias in Wireless Handsets
VCO and GaAsFET Supplies
MAX865C/D
MAX865EUA
-40°C to +85°C
8 µMAX
Split Supply from 3 Ni Cells or 1 Li+ Cell
Low-Cost Split Supply for Low-Voltage
Data-Acquisition Systems
__________Typ ic a l Op e ra t in g Circ u it
Split Supply for Analog Circuitry
LCD Panels
V
IN
(+1.5V to +6.0V)
__________________P in Co n fig u ra t io n
IN
C1+
MAX865
+2*V
V+
V-
IN
TOP VIEW
C1-
C2+
1
2
3
4
8
7
6
5
C1-
C2+
C2-
C1+
V+
-2*V
IN
MAX865
C2-
IN
GND
GND
V-
µMAX
GND
GND
+V to ±2V CONVERTER
IN
IN
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
Co m p a c t , Du a l-Ou t p u t Ch a rg e P u m p
ABSOLUTE MAXIMUM RATINGS
V+ to GND.................................................................+12V, -0.3V
IN to GND.................................................................+6.2V, -0.3V
V- to GND ..................................................................-12V, +0.3V
V- Output Current .............................................................100mA
V- Short-Circuit to GND ................................................Indefinite
Operating Temperature Range
MAX865EUA .....................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
Continuous Power Dissipation (T = +70°C)
A
µMAX (derate 4.1mW/°C above +70°C) .......................330mW
MAX865
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
(V = 5V, C1 = C2 = C3 = C4 = 3.3µF, T = T
to T , unless otherwise noted. Typical values are at T = +25°C.)
MAX A
IN
A
MIN
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Minimum Supply Voltage
Maximum Supply Voltage
R
R
= 10kΩ
= 10kΩ
2.0
1.5
0.6
24
V
V
LOAD
6.0
1.05
1.15
32.5
34
LOAD
T
A
= +25°C
Supply Current
mA
kHz
T
A
= -40°C to +85°C (Note 1)
= +25°C
T
A
19.5
18
Oscillator Frequency
T
A
= -40°C to +85°C (Note 1)
T
= +25°C
150
75
200
280
100
140
A
I
I
V-
= 1mA,
= 0mA
V+
T
A
= T
to T
MIN
MAX
MAX
Output Resistance
Ω
T
A
= +25°C
V+ = 10V (forced),
= 1mA
I
V-
T
A
= T
to T
MIN
Power Efficiency
I = 5mA
L
85
99
98
%
%
V+, R = ∞
95
90
L
Voltage Conversion Efficiency
V-, R = ∞
L
Note 1: These specifications are guaranteed by design and are not production tested.
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(Circuit of Figure 1, V = 5V, T = +25°C, unless otherwise noted.)
IN
A
EFFICIENCY vs. OUTPUT CURRENT
EFFICIENCY vs. OUTPUT CURRENT
EFFICIENCY vs. OUTPUT CURRENT
(V = 2V)
IN
(V = 3.3V)
IN
(V = 5V)
IN
100
90
100
90
100
90
V+
V+
V-
V+
V-
80
80
80
V-
70
60
50
40
30
20
10
0
70
60
50
40
30
20
10
0
70
60
50
40
30
20
10
0
1.0
OUTPUT CURRENT (mA)
0
0.5
1.5
2.0
2.5
0
1
2
3
4
5
6
7
8
0
2
4
6
8
10 12 14 16 18
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
2
_______________________________________________________________________________________
Co m p a c t , Du a l-Ou t p u t Ch a rg e P u m p
MAX865
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(Circuit of Figure 1, V = 5V, T = +25°C, unless otherwise noted.)
IN
A
OUTPUT VOLTAGE vs.
OUTPUT CURRENT
OUTPUT VOLTAGE RIPPLE
vs. PUMP CAPACITANCE
OUTPUT CURRENT
vs. PUMP CAPACITANCE
10
8
400
350
7
V+
| |
= 4.75V, V+ + V- = 16V
C1 = C2 = C3 = C4
V
IN
6
5
6
|
|
|
|
|
|
A: V+, IN = 4.75V, V+ + V- = 16V
B: V+, IN = 3.15V, V+ + V- = 10V
C: V+, IN = 1.90V, V+ + V- = 6V
D: V-, IN = 4.75V, V+ + V- = 16V
E: V-, IN = 3.15V, V+ + V- = 10V
F: V-, IN = 1.90V, V+ + V- = 6V
300
250
200
150
100
50
V-
4
2
| |
= 3.15V, V+ + V- = 10V
V
IN
| |
|
|
BOTH V+ AND
V- LOADED EQUALLY
4
3
2
1
0
|
|
0
-2
-4
-6
-8
-10
C1 = C2 = C3 = C4 = 3.3µF
F
| |
= 1.90V, V+ + V- = 6V
V
IN
V
IN
= 4.75V
A
E
B
D
V-
C
C1 = C2 = C3 = C4
V+
12
0
0
2
4
6
8
10
14
0
5
10 15 20 25 30 35 40 45 50
0
5
10 15 20 25 30 35 40 45 50
OUTPUT CURRENT (mA)
PUMP CAPACITANCE (µF)
PUMP CAPACITANCE (µF)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
OUTPUT RESISTANCE
vs. TEMPERATURE
1000
300
C1 = C2 = C3 = C4 = 3.3µF
V-, V = 3.3V
C1 = C2 = C3 = C4 = 3.3µF
900
800
IN
250
200
150
700
600
500
400
300
200
100
0
V-, V = 5.0V
IN
100
50
V+, V = 3.3V
IN
V+, V = 5.0V
IN
0
-35
25 45
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
SUPPLY VOLTAGE (V)
-55
-15
5
65 85 105 125
TEMPERATURE (°C)
PUMP FREQUENCY
vs. TEMPERATURE
OUTPUT RESISTANCE
vs. SUPPLY VOLTAGE
27
25
250
200
V
IN
= 5.0V
V-
V
= 3.3V
= 2.0V
23
21
IN
150
100
50
V+
V
IN
19
17
C1 = C2 = C3 = C4 = 3.3µF
C1 = C2 = C3 = C4 = 3.3µF
15
0
-40 -20
0
20
40
60
80 100
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
_______________________________________________________________________________________
3
Co m p a c t , Du a l-Ou t p u t Ch a rg e P u m p
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(Circuit of Figure 1, V = 5V, T = +25°C, unless otherwise noted.)
IN
A
OUTPUT RIPPLE
(C1 = C2 = C3 = C4 = 1µF)
OUTPUT RIPPLE
(C1 = C2 = C3 = C4 = 3.3µF)
MAX865
V- OUTPUT
20mV/div
V- OUTPUT
10mV/div
V+ OUTPUT
50mV/div
V+ OUTPUT
10mV/div
10µs/div
10µs/div
V
IN
= 4.75V, 1mA LOAD
V
IN
= 4.75V, 1mA LOAD
_____________________P in De s c rip t io n
PIN
NAME
FUNCTION
V
IN
Negative Terminal of the Flying Boost
Capacitor
C1-
1
3.3µF
3.3µF
C1+
C1-
Positive Terminal of the Flying
Inverting Capacitor
OUT+
2
3
C2+
C2-
I +
V
C2+
V+
IN
MAX865
Negative Terminal of the Flying
Inverting Capacitor
3.3µF
3.3µF
R +
L
C2-
V-
4
5
6
7
V-
GND
IN
Output of the Inverting Charge Pump
Ground
GND
I -
V
Positive Power-Supply Input
Output of the Boost Charge Pump
R -
L
V+
Positive Terminal of the Flying Boost
Capacitor
OUT-
8
C1+
Figure 1. Test Circuit
_______________________________________________________________________________________
4
Co m p a c t , Du a l-Ou t p u t Ch a rg e P u m p
MAX865
a nd S7 op e n, s witc he s S6 a nd S8 c los e , a nd the
_______________De t a ile d De s c rip t io n
charge on capacitor C2 transfers to C4, generating the
negative supply. The eight switches are CMOS power
MOSFETs. Switches S1, S2, S4, and S5 are P-channel
devices, while switches S3, S6, S7, and S8 are N-chan-
nel devices.
The MAX865 contains all the circuitry needed to imple-
me nt a volta ge d oub le r/inve rte r. Only four e xte rna l
capacitors are needed. These may be polarized elec-
trolytic or ceramic capacitors with values ranging from
1µF to 100µF.
Ch a rg e -P u m p Ou t p u t
The MAX865 is not a voltage regulator: the output
source resistance of either charge pump is approxi-
Figure 2a shows the ideal operation of the positive volt-
age doubler. The on-chip oscillator generates a 50%
duty-c yc le c loc k sig na l. During the first ha lf c yc le ,
switches S2 and S4 open, switches S1 and S3 close,
mately 150Ω at room temperature with V = +5V, and
IN
V+ and V- will approach +10V and -10V, respectively,
when lightly loaded. Both V+ and V- will droop toward
GND as the current draw from either V+ or V- increas-
es, since V- is derived from V+. Treating each convert-
e r s e p a ra te ly, the d roop of the ne g a tive s up p ly
and capacitor C1 charges to the input voltage (V ).
During the s e c ond ha lf c yc le , s witc he s S1 a nd S3
open, switches S2 and S4 close, and capacitor C1 is
IN
level shifted upward by V . Assuming ideal switches
IN
and no load on C3, charge transfers into C3 from C1
(V
DROOP-
) is the product of the current draw from V-
such that the voltage on C3 will be 2V , generating the
IN
(I ) and the source resistance of the negative convert-
V-
positive supply output (V+).
er (RS-):
Figure 2b illustrates the ideal operation of the negative
converter. The switches of the negative converter are
out of phase with the positive converter. During the
s e c ond ha lf c yc le , s witc he s S6 a nd S8 op e n a nd
s witc he s S5 a nd S7 c los e , c ha rg ing C2 from V+
V
= I x RS -
V-
DROOP -
The droop of the p ositive supply (V
) is the
DROOP+
product of the current draw from the positive supply
(I ) a nd the sourc e re sista nc e of the positive
(pumped up to 2V by the positive charge pump) to
IN
LOAD+
GND. In the first half of the clock cycle, switches S5
a)
b)
V+
V+
S6
S8
S1
S3
C1+ S2
S5
C2+
IN
GND
V-
C2
C3
C1
R +
L
I +
V
R -
L
I -
V
C4
S4
S7
I
N
GND
GND
C1-
C2-
Figure 2. Idealized Voltage Quadrupler: a) Positive Charge Pump; b) Negative Charge Pump
_______________________________________________________________________________________
5
Co m p a c t , Du a l-Ou t p u t Ch a rg e P u m p
converter (RS+), where I
and the external load on V+ (I ):
is the combination of I
V+
Effic ie n c y Co n s id e ra t io n s
Theoretically, a charge-pump voltage multiplier can
approach 100% power efficiency under the following
conditions:
LOAD+
V-
V
= I
x RS+ = I + I
x RS+
(
)
DROOP+
LOAD+
V+
V-
Determine V+ and V- as follows:
V+ = 2V - V
• The charge-pump switches have virtually no offset
and extremely low on-resistance.
IN
DROOP+
• The drive circuitry consumes minimal power.
MAX865
V- = (V+ - V
) = -(2V - V
- V
DROOP -
)
DROOP
IN DROOP+
• The impedances of the reservoir and pump capaci-
tors are negligible.
The output resistance for the positive and negative
charge pumps are tested and specified separately. The
positive charge pump is tested with V- unloaded. The
negative charge pump is tested with V+ supplied from
a n e xte rna l s ourc e , is ola ting the ne g a tive c ha rg e
pump.
For the MAX865, the energy loss per clock cycle is the
sum of the energy loss in the positive and negative
converters, as follows:
LOSS
= LOSS
1
+ LOSS
2
CYCLE
POS
NEG
Current draw from either V+ or V- is supplied by the
reservoir capacitor alone during one half cycle of the
clock. Calculate the resulting ripple voltage on either
output as follows:
=
C1 V + − 2 V +
V
IN
(
)
(
)
(
)
2
1
2
2
2
+
C2 V +
−
V −
(
)
(
)
1
The average power loss is simply:
= LOSS
V
=
I
(1 / f
) (1 / C
)
RESERVOIR
RIPPLE
LOAD
PUMP
2
P
x f
PUMP
where I
is the load on either V+ or V-. For the typi-
of 30kHz with 3.3µF reservoir capacitors, the
ripple is 25mV when I
most applications, the total load on V+ is the V+ load
current (I ) and the current taken by the negative
LOAD
LOSS
CYCLE
cal f
PUMP
Resulting in an efficiency of:
η = Total Output Power / Total Output Power − P
is 5mA. Remember that, in
LOAD
(
)
LOSS
V+
charge pump (I ).
V-
V
IN
3.3µF
3.3µF
3.3µF
3.3µF
1
2
8
7
1
2
8
7
C1-
C1-
C2-
C1+
V+
OUT+
IN
C1+
V+
MAX865
MAX865
C2+
3.3µF
3
4
3
4
6
5
6
5
IN
IN
C2-
V-
C2-
V-
GND
GND
GND
3.3µF
OUT-
Figure 3. Paralleling MAX865s
6
_______________________________________________________________________________________
Co m p a c t , Du a l-Ou t p u t Ch a rg e P u m p
MAX865
A substantial voltage difference exists between (V+ -
P a ra lle lin g De vic e s
Paralleling multiple MAX865s (Figure 3) reduces the
output resistance of both the positive and negative con-
verters. The effective output resistance is the output
resistance of one device divided by the number of
devices. Separate C1 and C2 charge-pump capacitors
are required for each MAX865, but the reservoir capac-
itors C3 and C4 can be shared.
VIN) and VIN for the positive pump, and between V+
and V- if the impedances of the pump capacitors
(C1 a nd C2) a re la rg e with re s p e c t to the ir outp ut
loads.
La rg e r va lue s of re s e rvoir c a p a c itors (C3 a nd C4)
reduce output ripple. Larger values of both pump and
reservoir capacitors improve power efficiency.
He a vy Ou t p u t Cu rre n t Lo a d s
When under heavy loads, where V+ is sourcing current
into V- (i.e., load current flows from V+ to V-, rather than
from supply to ground), do not allow the V- supply to
pull above ground. In applications where large currents
flow from V+ to V-, use a Schottky diode (1N5817)
between GND and V-, with the anode connected to
GND (Figure 4).
Ch a rg e -P u m p Ca p a c it o r S e le c t io n
To maintain the lowest output resistance, use capacitors
with low effective series resistance (ESR). The charge-
pump output resistance is a function of C1, C2, C3, and
C4’s ESR. The re fore , minimizing the c ha rg e -p ump
capacitors’ ESR minimizes the total output resistance.
__________Ap p lic a t io n s In fo rm a t io n
P o s it ive a n d Ne g a t ive Co n ve rt e r
The MAX865 is most commonly used as a dual charge-
pump voltage converter that provides positive and neg-
ative outputs of two times a positive input voltage. The
Typical Operating Circuit shows that only four external
components are needed: capacitors C1 and C3 for the
positive pump, C2 and C4 for the negative pump. In
most applications, all four capacitors are low-cost,
3.3µF polarized electrolytics. For applications where PC
board space is at a premium and very low currents are
being drawn from the MAX865, 1µF capacitors may be
used for the pump capacitors C1 and C2, with 1µF
reservoir capacitors C3 and C4. Capacitors C2 and C4
must be rated at 12V or greater.
La yo u t a n d Gro u n d in g
Good layout is important, primarily for good noise per-
formance. To ensure good layout:
• Mount all components as close together as possible
• Keep traces short to minimize parasitic inductance
and capacitance
• Use a ground plane.
GND
MAX865
V-
Figure 4. A Schottky diode protects the MAX865 when large
currents flow from V+ to V-.
_______________________________________________________________________________________
7
Co m p a c t , Du a l-Ou t p u t Ch a rg e P u m p
___________________Ch ip To p o g ra p h y
TRANSISTOR COUNT: 80
SUBSTRATE CONNECTED TO V+
C1-
C1+
MAX865
C2+
V+
IN
0. 084"
(2. 13mm)
C2-
V-
GND
0. 058"
(1. 47mm)
________________________________________________________P a c k a g e In fo rm a t io n
INCHES
MILLIMETERS
DIM
MIN
0.036
MAX
0.044
0.008
0.014
0.007
0.120
0.120
MIN
0.91
0.10
0.25
0.13
2.95
2.95
MAX
1.11
0.20
0.36
0.18
3.05
3.05
A
C
A1 0.004
α
A
B
C
D
E
e
0.010
0.005
0.116
0.116
0.101mm
0.004 in
e
B
A1
L
0.0256
0.65
H
L
0.188
0.016
0°
0.198
0.026
6°
4.78
0.41
0°
5.03
0.66
6°
α
21-0036D
E
H
8-PIN µMAX
MICROMAX SMALL-OUTLINE
PACKAGE
D
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 4 0 8 -7 3 7 -7 6 0 0
© 1997 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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