MAX868.pdf 데이터시트 (총 12 페이지) - 파일 다운로드 MAX868 데이타시트 다운로드

No Preview Available !

19-1290; Rev 1; 2/98
Regulated, Adjustable -2x
Inverting Charge Pump
General Description
The MAX868 inverting charge pump provides a low-cost
and compact means of generating a regulated negative
voltage up to -2 x VIN from a positive input voltage
between 1.8V and 5.5V. It uses a pulse-frequency-
modulation (PFM) control scheme to generate the regulat-
ed negative output voltage. PFM operation is obtained
by gating the internal 450kHz oscillator on and off as
needed to maintain output voltage regulation. This
unique on-demand switching scheme gives the MAX868
excellent light-load efficiency without degrading its full-
load operation (up to 30mA), permitting smaller capaci-
tors to take advantage of the oscillator’s high switching
frequency.
The MAX868 requires no inductors; only four capacitors
are required to build a complete DC-DC converter.
Output voltage regulation is achieved by adding just two
resistors. The MAX868 comes in a 10-pin µMAX pack-
age, which is only 1.11mm high and occupies just half
the board area of a standard 8-pin SO.
________________________Applications
Small LCD Panels
Cell Phones
Cordless Phones
Camcorders
Handy-Terminals, PDAs
Medical Instruments
Battery-Operated Equipment
Configuration
TOP VIEW
____________________________Features
o Regulated Negative Output Voltage
(up to -2 x VIN)
o Ultra-Small, 10-Pin µMAX Package
o On-Demand Switching at up to 450kHz
o 30µA Quiescent Supply Current
o Requires Only Four Small External Capacitors
o 1.8V to 5.5V Input Voltage Range
o 0.1µA Logic-Controlled Shutdown
o Up to 30mA Output Current
Ordering Information
PART
TEMP. RANGE
MAX868C/D
0°C to +70°C
MAX868EUB
-40°C to +85°C
*Dice are tested at TA = +25°C.
PIN-PACKAGE
Dice*
10 µMAX
Typical Operating Circuit
VIN = 1.8V TO 5.5V
1µF
SHDN IN
GND 1
OUT 2
C1- 3
PGND 4
C1+ 5
MAX868
µMAX
10 FB
9 SHDN
8 C2+
7 IN
6 C2-
0.1µF
0.1µF
MAX868
C1+ FB
C1-
C2+ OUT
C2-
PGND GND
VOUT = 0V TO -2 x VIN
2.2µF
________________________________________________________________ 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.

No Preview Available !

Regulated, Adjustable -2x
Inverting Charge Pump
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................-0.3V to +6V
OUT to GND ...........................................................+0.3V to -12V
IN to OUT.................................................................-0.3V to -17V
C1+ to GND ........................................(VIN - 12V) to (VIN + 0.3V)
C1- to GND.............................................................+0.3V to -12V
C2+ to GND ....................................................(VIN + 0.3V) to -6V
C2- to GND...............................................................+0.3V to -6V
SHDN, FB to GND .......................................-0.3V to (VIN + 0.3V)
PGND to GND .......................................................-0.3V to +0.3V
Output Current ....................................................................35mA
Short-Circuit Duration.................................................Continuous
Continuous Power Dissipation (TA = +70°C)
10-pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW
Operating Temperature Range
MAX868EUB ....................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
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
(VIN = +3.3V, SHDN = IN, C1 = C2 = 0.22µF, CIN = 1µF, COUT = 10µF, TA = 0°C to +85°C, unless otherwise noted. Typical values
are at TA = +25°C.)
PARAMETER
Supply-Voltage Range
Supply Current
Shutdown Current
Oscillator Frequency
Closed-Loop Output
Resistance
Open-Loop Output
Resistance
FB Trip Point
Output Current
FB Input Bias Current
SHDN Input Threshold
SHDN Input Bias Current
SYMBOL
VIN
IIN
IIN,SHDN
fOSC
ROUT,CL
ROUT
IOUT
VIL
VIH
CONDITIONS
RL = 3kto GND
No load, VFB = -50mV
FB = IN
No load, SHDN = GND
VFB = 50mV
TA = +25°C
TA = 0°C to +85°C
VOUT = -5V
IOUT = 5mA, FB = IN
TA = +25°C
TA = 0°C to +85°C
SHDN = GND (OUT pulls to GND)
VIN = 1.8V to 5.5V
TA = +25°C
TA = 0°C to +85°C
Closed loop
VIN = 3.3V, VOUT = -5V
VIN = 5V, VOUT = -3.3V
VIN = 1.8V to 5.5V, TA = +25°C
VIN = 1.8V to 5.5V
VIN = 5.5V, SHDN = IN or GND
MIN TYP MAX UNITS
1.8 5.5 V
30 50 µA
5 mA
0.1 1 µA
293 450 607
kHz
270 630
0.2
70 100
125
15 50
-30 30 mV
-40 40 mV
12
mA
30
-50 1
50 nA
0.3VIN
0.7VIN
V
-100 1 100 nA
2 _______________________________________________________________________________________

No Preview Available !

Regulated, Adjustable -2x
Inverting Charge Pump
ELECTRICAL CHARACTERISTICS
(VIN = +3.3V, C1 = C2 = 0.22µF, CIN = 1µF, COUT = 10µF, TA = -40°C to +85°C, unless otherwise noted. (Note 1)
PARAMETER
Supply-Voltage Range
Supply Current
Shutdown Current
Oscillator Frequency
Open-Loop Output
Resistance
FB Trip Point
FB Input Bias Current
SHDN Input Threshold
SHDN Input Bias Current
SYMBOL
VIN
IIN
IIN,SHDN
fOSC
ROUT
VIL
VIH
CONDITIONS
RL = 3kto GND
No load, VFB = -50mV
No load, SHDN = GND
VFB = 50mV
IOUT = 5mA, FB = IN
SHDN = GND (OUT pulls to GND)
VIN = 1.8V to 5.5V
VIN = 1.8V to 5.5V
VIN = 1.8V to 5.5V
VIN = 5.5V, SHDN = IN or GND
MIN TYP MAX UNITS
1.8 5.5 V
55 µA
1 µA
270 630 kHz
125
50
-40 40 mV
-100
100 nA
0.3VIN
-100
0.7VIN
100
V
nA
Note 1: Specifications to -40°C are guaranteed by design, not production tested.
__________________________________________Typical Operating Characteristics
(Circuit of Figure 5, TA = +25°C, unless otherwise noted.)
LOAD-REGULATION ERROR
vs. LOAD CURRENT
(VIN = 5V)
5
0
-5 VOUT = -5V
-10
VOUT = -7.5V
-15
-20
VOUT = -3.3V
-25
-30
-35
0
5 10 15 20 25 30 35 40 45 50
LOAD CURRENT (mA)
3
0
-3
-6
-9
-12
-15
0
LOAD-REGULATION ERROR
vs. LOAD CURRENT
(VIN = 3.3V)
VOUT = -5V
VOUT = -3.3V
5 10 15 20
LOAD CURRENT (mA)
25
MAXIMUM SWITCHING FREQUENCY
vs. TEMPERATURE
500
FB = IN
490
480 VIN = 5V
470
460
450
440
VIN = 3.3V
430
420
410
400
-40
-20
VIN = 2V
0 20 40 60
TEMPERATURE (°C)
80 100
_______________________________________________________________________________________ 3

No Preview Available !

Regulated, Adjustable -2x
Inverting Charge Pump
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 5, TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(VIN = 5V)
80
70
60 VOUT = -7.5V
EFFICIENCY vs. LOAD CURRENT
(VIN = 3.3V)
80
70
VOUT = -5V
60
EFFICIENCY vs. LOAD CURRENT
(VIN = 5V)
80
CIRCUIT OF FIGURE 6
70 VOUT = -3.3V
60
50 50
40
VOUT = -5V
40
VOUT = -3.3V
50
40
VOUT = -2.5V
30 30
VOUT = -3.3V
20 20
10 10
30
20
10
0
0.01
0.1 1 10
LOAD CURRENT (mA)
100
OPEN-LOOP OUTPUT IMPEDANCE
vs. TEMPERATURE
(FB = IN, VOUT = -2 x VIN)
200
180
160
140
120 VIN = 2V
100 VIN = 3.3V
80
60
40 VIN = 5V
20
0
-40 -20
0 20 40 60
TEMPERATURE (°C)
80 100
0
0.01
0.1 1 10
LOAD CURRENT (mA)
100
OPEN-LOOP OUTPUT IMPEDANCE
vs. TEMPERATURE
(FB = IN, VOUT = -VIN)
200
CIRCUIT OF FIGURE 6
180
160
140
120
100 VIN = 2V
80
60 VIN = 3.3V
40
20
0
-40
-20
VIN = 5V
0 20 40 60 80 100
TEMPERATURE (°C)
0
0.01
0.1 1 10
LOAD CURRENT (mA)
100
LOAD-TRANSIENT RESPONSE
10mA/div
20mV/div
200µs/div
VIN = 5V, VOUT = -5V, IOUT = 1mA TO 11mA STEP
OUTPUT VOLTAGE RIPPLE
(COUT = 10µF TANTALUM)
OUTPUT VOLTAGE RIPPLE
(COUT = 10µF CERAMIC)
OUTPUT VOLTAGE RIPPLE
20mV/div
20mV/div
20mV/div
20µs/div
VIN = 3.3V, VOUT = -3.3V, ILOAD = 5mA,
VOUT AC COUPLED (20mV/div), COUT = 10µF (AVX TPS)
20µs/div
VIN = 3.3V, VOUT = -3.3V, ILOAD = 5mA,
VOUT AC COUPLED (20mV/div), COUT = 10µF CERAMIC
20µs/div
VIN = 3.3V, VOUT = -3.3V, ILOAD = 5mA,
VOUT AC COUPLED (20mV/div), COUT = 2.2µF CERAMIC
4 _______________________________________________________________________________________

No Preview Available !

Regulated, Adjustable -2x
Inverting Charge Pump
Pin Description
PIN NAME
FUNCTION
1 GND Analog Ground
2 OUT Charge-Pump Output
3 C1- Negative Terminal of Flying Capacitor C1
4 PGND Power Ground
5 C1+ Positive Terminal of Flying Capacitor C1
6 C2- Negative Terminal of Flying Capacitor C2
7 IN Supply-Voltage Input. Input voltage range is 1.8V to 5.5V.
8 C2+ Positive Terminal of Flying Capacitor C2
9
SHDN
Active-Low Shutdown Input. Connect SHDN to GND to put the MAX868 in shutdown mode and reduce sup-
ply current to 0.1µA. Connect to IN for normal operation. OUT is actively pulled to GND in shutdown.
10
FB
Feedback Input. Connect FB to a resistor divider for a regulated output voltage. Connect to IN to generate
an unregulated -2 x VIN output voltage.
Detailed Description
The MAX868 inverting charge pump uses pulse-
frequency-modulation (PFM) control to generate a reg-
ulated negative output voltage up to -2 x VIN. PFM
operation is obtained by enabling the internal 450kHz
oscillator as needed to maintain output voltage regula-
tion. This control scheme reduces supply current at
light loads and permits the use of small capacitors.
The functional diagram shown in Figure 1 indicates the
two phases of MAX868 operation: charge phase (Φ1)
and discharge phase (Φ2). In charge phase, the
switches on the left-hand side close, and the switches
on the right-hand side open. In the discharge phase,
the inverse occurs.
Figure 2 illustrates that in charge phase, both flying
capacitors are charged in parallel. The load is serviced
entirely by the charge stored in the output capacitor.
Figure 3 demonstrates the series connection of the fly-
ing capacitors in the discharge phase. The series com-
bination of the flying capacitors, when connected to the
output capacitor, transfers charge to the output in order
to maintain output voltage regulation. In normal opera-
tion, the MAX868 operates predominantly in charge
phase, switching to discharge phase only as needed to
maintain a regulated output.
IN
SHDN
C2+
C2-
C1+
C1-
Φ1 Φ2
OSCILLATOR
Figure 1. Functional Diagram
OUT
FB
COUT
VREF
_______________________________________________________________________________________ 5