Rainbow Electronics MAX1779 User Manual
General Description
The MAX1779 triple-output DC-DC converter provides
highly efficient regulated voltages required by small
active matrix, thin-film transistor (TFT) liquid-crystal displays (LCDs). One high-power DC-DC converter and
two low-power charge pumps convert the +2.7V to
+5.5V input supply voltage into three independent output voltages.
The primary high-power DC-DC converter generates a
boosted output voltage (V
MAIN
) up to 13V that is regu-
lated within ±1%. The low-power BiCMOS control circuitry and the low on-resistance (1Ω) of the integrated
power MOSFET allows efficiency up to 91%. The
250kHz current-mode pulse-width modulation (PWM)
architecture provides fast transient response and
allows the use of ultra-small inductors and ceramic
capacitors.
The dual charge pumps independently regulate one
positive output (V
POS
) and one negative output (V
NEG
).
These low-power outputs use external diode and
capacitor stages (as many stages as required) to regulate output voltages up to +40V and down to -40V. A
proprietary regulation algorithm minimizes output ripple, as well as capacitor sizes for both charge pumps.
The MAX1779 is available in the ultra-thin TSSOP package (1.1mm max height).
________________________Applications
TFT Active-Matrix LCD Displays
Passive-Matrix LCD Displays
PDAs
Digital-Still Cameras
Camcorders
Features
♦ Three Integrated DC-DC Converters
♦ 250kHz Current-Mode PWM Boost Regulator
Up to +13V Main High-Power Output
±1% Accuracy
High Efficiency (91%)
♦ Dual Charge-Pump Outputs
Up to +40V Positive Charge-Pump Output
Down to -40V Negative Charge-Pump Output
♦ Internal Supply Sequencing
♦ Internal Power MOSFETs
♦ +2.7V to +5.5V Input Supply
♦ 0.1µA Shutdown Current
♦ 0.5mA Quiescent Current
♦ Internal Soft-Start
♦ Power-Ready Output
♦ Ultra-Small External Components
♦ Thin TSSOP Package (1.1mm max)
MAX1779
Low-Power Triple-Output TFT LCD DC-DC
Converter
________________________________________________________________ Maxim Integrated Products 1
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
RDY TGND
LX
PGND
SUPP
DRVP
SUPN
DRVN
SHDN
TOP VIEW
MAX1779
TSSOP
FB
INTG
REF
IN
GND
FBP
FBN
Pin Configuration
19-1795; Rev 0; 11/00
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Ordering Information
Typical Operating Circuit appears at end of data sheet.
16 TSSOP
PIN-PACKAGETEMP. RANGE
-40°C to +85°CMAX1779EUE
PART
MAX1779
Low-Power Triple-Output TFT LCD DC-DC
Converter
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN= +3.0V, SHDN = IN, V
SUPP
= V
SUPN
= +10V, TGND = PGND = GND, C
REF
= 0.22µF, C
INTG
= 2200pF, TA= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°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.
IN, SHDN, TGND to GND .........................................-0.3V to +6V
DRVN to GND .........................................-0.3V to (V
SUPN
+ 0.3V)
DRVP to GND..........................................-0.3V to (V
SUPP
+ 0.3V)
PGND to GND.....................................................................±0.3V
RDY to GND ...........................................................-0.3V to +14V
LX, SUPP, SUPN to PGND .....................................-0.3V to +14V
INTG, REF, FB, FBN, FBP to GND...............-0.3V to (V
IN
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
16-Pin TSSOP (derate 9.4mW/°C above +70°C) ..........755mW
Operating Temperature Range
MAX1779EUE ..................................................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Input Supply Range V
IN
2.7 5.5 V
Input Undervoltage Threshold
VIN rising, 40mV hysteresis (typ) 2.2 2.4 2.6 V
IN Quiescent Supply Current I
IN
VFB = V
FBP
= +1.5V, V
FBN
= -0.2V 0.5 1 mA
SUPP Quiescent Current I
SUPP
V
FBP
= +1.5V
mA
SUPN Quiescent Current I
SUPN
V
FBN
= -0.1V
mA
IN Shutdown Current V
SHDN
= 0, V
IN
= +5V 0.1 10 µA
SUPP Shutdown Current V
SHDN
= 0, V
SUPP
= +13V 0.1 10 µA
SUPN Shutdown Current V
SHDN
= 0, V
SUPN
= +13V 0.1 10 µA
MAIN BOOST CONVERTER
Output Voltage Range
V
IN
13 V
FB Regulation Voltage V
FB
V
FB Input Bias Current I
FB
VFB = +1.25V, INTG = GND -50 50 nA
Operating Frequency f
OSC
Oscillator Maximum Duty Cycle
79 85 92 %
Load Regulation I
MAIN
= 0 to 50mA, V
MAIN
= +5V 0.1 %
Line Regulation 0.1
Integrator Gm
µs
LX Switch On-Resistance
)
ILX = 100mA 1.0 2.0 Ω
LX Leakage Current I
LX
VLX = +13V
20 µA
LX Current Limit I
LIM
mA
Maximum RMS LX Current
mA
FB Fault Trip Level Falling edge
1.1
V
POSITIVE CHARGE PUMP
V
SUPP
Input Supply Range
2.7 13 V
V
UVLO
0.25 0.55
0.25 0.55
V
MAIN
R
LX(ON
V
SUPP
1.235 1.248 1.261
212 250 288 kHz
320
0.01
350 450 650
250
1.07
1.14
% / V
MAX1779
Low-Power Triple-Output TFT LCD DC-DC
Converter
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VIN= +3.0V, SHDN = IN, V
SUPP
= V
SUPN
= +10V, TGND = PGND = GND, C
REF
= 0.22µF, C
INTG
= 2200pF, TA= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Operating Frequency
0.5 ×
Hz
FBP Regulation Voltage V
FBP
V
FBP Input Bias Current I
FBP
V
FBP
= +1.5V -50 50 nA
DRVP PCH On-Resistance
310Ω
V
FBP
= +1.200V 1.5 5 Ω
DRVP NCH On-Resistance
V
FBP
= +1.300V 20 kΩ
FBP Power-Ready Trip Level Rising edge
V
FBP Fault Trip Level Falling edge
V
Maximum RMS DRVP Current 0.1 A
NEGATIVE CHARGE PUMP
V
SUPN
Input Supply Range
2.7 13 V
Operating Frequency
0.5 ×
Hz
FBN Regulation Voltage V
FBN
-50 0 50
FBN Input Bias Current I
FBN
V
FBN
= -0.05V -50 50 nA
DRVN PCH On-Resistance
310Ω
V
FBN
= +0.050V 1.5 5 Ω
DRVN NCH On-Resistance
V
FBN
= -0.050V 20 kΩ
FBN Power-Ready Trip Level Falling edge 80
165
FBN Fault Trip Level Rising edge
Maximum RMS DRVN Current 0.1 A
REFERENCE
Reference Voltage V
REF
-2µA < I
REF
< 50µA
V
Reference Undervoltage
Threshold
V
REF
rising 0.9
1.2 V
LOGIC SIGNALS
SHDN Input Low Voltage 0.25V hysteresis (typ) 0.9 V
SHDN Input High Voltage 2.1 V
SHDN Input Current
1 µA
RDY Output Low Voltage I
SINK
= 2mA
0.5 V
RDY Output High Voltage V
RDY
= +13V
1 µA
V
I
SUPN
SHDN
1.20 1.25 1.30
1.09 1.13 1.16
1.231 1.25 1.269
f
OSC
1.11
f
OSC
120
140 mV
1.05
0.01
0.25
0.01
mV
mV
MAX1779
Low-Power Triple-Output TFT LCD DC-DC
Converter
4 _______________________________________________________________________________________
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
Input Supply Range V
IN
2.7 5.5 V
Input Undervoltage Threshold
VIN rising, 40mV hysteresis (typ) 2.2 2.6 V
IN Quiescent Supply Current I
IN
VFB = V
FBP
= +1.5V, V
FBN
= -0.2V 1 mA
SUPP Quiescent Current
V
FBP
= +1.5V
mA
SUPN Quiescent Current
V
FBN
= -0.1V
mA
IN Shutdown Current V
SHDN
= 0, VIN = +5V 10 µA
SUPP Shutdown Current V
SHDN
= 0, V
SUPP
= +13V 10 µA
SUPN Shutdown Current V
SHDN
= 0, V
SUPN
= +13V 10 µA
MAIN BOOST CONVERTER
Output Voltage Range
V
IN
13 V
FB Regulation Voltage V
FB
V
FB Input Bias Current I
FB
VFB = +1.25V, INTG = GND -50 50 nA
Operating Frequency f
OSC
kHz
Oscillator Maximum Duty Cycle
79 92 %
LX Switch On-Resistance
)
I
LX
= 100mA 2.0 Ω
LX Leakage Current
I
LX
VLX = +13V 20 µA
LX Current Limit I
LIM
mA
FB Fault Trip Level Falling edge
V
POSITIVE CHARGE PUMP
SUPP Input Supply Range
2.7 13 V
FBP Regulation Voltage V
FBP
V
FBP Input Bias Current I
FBP
V
FBP
= +1.5V -50 50 nA
DRVP PCH On-Resistance 10 Ω
V
FBP
= +1.200V 5 Ω
DRVP NCH On-Resistance
V
FBP
= +1.300V 20 kΩ
FBP Power-Ready Trip Level Rising edge
V
NEGATIVE CHARGE PUMP
SUPN Input Supply Range
2.7 13 V
FBN Regulation Voltage V
FBN
-50 50 mV
FBN Input Bias Current
I
FBN
V
FBN
= -0.05V -50 50 nA
DRVN PCH On-Resistance
10 Ω
V
FBN
= +0.050V 5 Ω
DRVN NCH On-Resistance
V
FBN
= -0.050V 20 kΩ
FBN Power-Ready Trip Level Falling edge 80
mV
REFERENCE
Reference Voltage V
REF
-2µA < I
REF
< 50µA
V
Reference Undervoltage
V
REF
rising 0.9 1.2 V
ELECTRICAL CHARACTERISTICS
(VIN= +3.0V, SHDN = IN, V
SUPP
= V
SUPN
= +10V, TGND = PGND = GND, C
REF
= 0.22µF, C
INTG
= 2200pF, TA= -40°C to +85°C,
unless otherwise noted.) (Note 1)
V
UVLO
I
SUPP
I
SUPN
V
MAIN
R
LX(ON
1.225 1.271
195 305
350 700
1.07 1.14
V
SUPP
1.20 1.30
1.09 1.16
V
SUPN
1.223 1.269
0.55
0.55
165
MAX1779
Low-Power Triple-Output TFT LCD DC-DC
Converter
_______________________________________________________________________________________ 5
4.98
4.99
5.00
5.01
5.02
0 50 100 150 200
MAIN OUTPUT VOLTAGE vs. LOAD CURRENT
(L = 10µH, 5V OUTPUT)
MAX1779-01
I
MAIN
(mA)
V
MAIN
(V)
VIN = +3.0V
VIN = +4.2V
FIGURE 6
50
60
70
90
100
0 50 100 150 200
MAIN STEP-UP CONVERTER EFFICIENCY
vs. LOAD CURRENT
(L = 10µH, 5V OUTPUT)
MAX1779-02
I
MAIN
(mA)
EFFICIENCY (%)
VIN = +3.0V
VIN = +4.2V
80
FIGURE 6
4.98
4.99
5.00
5.01
5.02
010050 150 200 250 300
MAIN OUTPUT VOLTAGE vs. LOAD CURRENT
(L = 33µH, 5V OUTPUT)
MAX1779-03
I
MAIN
(mA)
V
MAIN
(V)
VIN = +4.2V
VIN = +3.0V
FIGURE 5
50
60
70
80
90
100
0 10050 150 200 250 300
MAIN STEP-UP CONVERTER EFFICIENCY
vs. LOAD CURRENT
(L = 33µH, 5V OUTPUT)
MAX1779-04
I
MAIN
(mA)
EFFICIENCY (%)
VIN = +4.2V
VIN = +3.0V
FIGURE 5
9.96
9.98
10.00
10.02
10.04
0 50 100 150
MAIN OUTPUT VOLTAGE vs. LOAD CURRENT
(L = 33µH, 10V OUTPUT)
MAX1779-05
I
MAIN
(mA)
V
MAIN
(V)
VIN = +3.3V
VIN = +5.0V
FIGURE 5
50
60
70
80
90
100
0 50 100 150
MAIN STEP-UP CONVERTER EFFICIENCY
vs. LOAD CURRENT
(L = 33µH, 10V OUTPUT)
MAX1779-06
I
MAIN
(mA)
EFFICIENCY (%)
VIN = +5.5V
VIN = +3.3V
FIGURE 5
Typical Operating Characteristics
(Circuit of Figure 5, VIN= +3.3V, TA= +25°C, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS (continued)
(VIN= +3.0V, SHDN = IN, V
SUPP
= V
SUPN
= +10V, TGND = PGND = GND, C
REF
= 0.22µF, C
INTG
= 2200pF, TA= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
LOGIC SIGNALS
SHDN Input Low Voltage 0.25V hysteresis (typ) 0.9 V
SHDN Input High Voltage 2.1 V
SHDN
Input Current
1 µA
RDY Output Low Voltage I
SINK
= 2mA 0.5 V
RDY Output High Leakage V
RDY
= +13V 1 µA
Note 1: Specifications to -40°C are guaranteed by design, not production tested.
I
SHDN
4.0µs/div
RIPPLE WAVEFORMS
MAX1779-14
A. V
MAIN
= 5V, I
MAIN
= 100mA, 10mV/div
B. V
NEG
= -8V, I
NEG
= 1mA, 5mV/div
C. V
POS
= 12V, I
POS
= 1mA, 5mV/div, FIGURE 5
5V
12V
-8V
A
B
C
100µs/div
LOAD TRANSIENT
(L = 10µH, 500µs PULSE)
MAX1779-15
A. V
MAIN
= 5V, 50mV/div
B. V
MAIN
= 5mA to 50mA, 25mA/div
FIGURE 6
5.0V
0
4.9V
A
B
5.1V
50mA
MAX1779
Low-Power Triple-Output TFT LCD DC-DC
Converter
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(Circuit of Figure 5, VIN= +3.3V, TA= +25°C, unless otherwise noted.)
11.64
11.76
12.00
11.88
12.12
12.24
0105 15202530
POSITIVE CHARGE-PUMP OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1779-10
I
POS
(mA)
V
POS
(V)
V
SUPP
= +7V
V
SUPP
= +6V
V
SUPP
= +5V
30
50
40
70
60
90
80
100
010155 202530
POSITIVE CHARGE-PUMP EFFICIENCY
vs. LOAD CURRENT
MAX1779-11
I
POS
(mA)
V
POS
(V)
V
SUPP
= +5V
V
SUPP
= +6V
V
SUPP
= +7V
V
POS
= +12V
200
220
240
260
280
300
2.5 3.53.0 4.0 4.5 5.0
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
MAX1779-12
INPUT VOLTAGE (V)
SWITCHING FREQUENCY (kHz)
1.244
1.248
1.246
1.252
1.250
1.254
1.256
02010 30 40 50
REFERENCE VOLTAGE
vs. REFERENCE LOAD CURRENT
MAX1779-13
I
REF
(µA)
V
REF
(V)
50
60
70
80
90
100
0 10050 150 200 250
EFFICIENCY vs. LOAD CURRENT
(BOOST CONVERTER AND CHARGE PUMPS)
MAX1779-07
I
MAIN
(mA)
EFFICIENCY (%)
V
MAIN
= +5V
TWO-STAGE
CHARGE PUMPS
V
MAIN
= +10V
SINGLE-STAGE
CHARGE PUMPS
V
NEG
= -8V, I
NEG
= 1mA
V
POS
= +12V, I
POS
= 1mA
-8.08
-8.04
-8.00
-7.96
-7.92
-7.88
-7.84
-7.80
-7.76
0 5 10 15 20
NEGATIVE CHARGE-PUMP OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1779-08
I
NEG
(mA)
V
NEG
(V)
V
SUPN
= +5V
V
SUPN
= +6V
V
SUPN
= +7V
30
50
40
70
60
90
80
100
NEGATIVE CHARGE-PUMP EFFICIENCY
vs. LOAD CURRENT
MAX1779-09
I
NEG
(mA)
EFFICIENCY (%)
0 5 10 15 20
V
SUPN
= +5V
V
NEG
= -8V
V
SUPN
= +6V
V
SUPN
= +7V
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