AIC1650
3-Cell, High-Efficiency, Inverting DC/DC
Converter
Analog Integrations Corporation
4F, 9, Industry E. 9th Rd, Science Based Industrial Park, Hsinchu Taiwan, ROC
www.analog.com.tw
DS-1650-02 Dec 27, 00
TEL: 886-3-5772500
FAX: 886-3-5772510
1
FEATURES
4V to 20V Input Voltage Operation.
Adjustable Output Voltage up to -40V.
Low Quiescent Current at 100
A.
Pulse Frequency Modulation Maintains High
Efficiency (max. 90%).
100KHz to 320KHz Switching Frequency.
Power-Saving Shutdown Mode (8
A Typical).
High Efficiency with Low Cost External PNP
Bipolar Transistor.
APPLICATIONS
Negative LCD Contrast Bias for
1. Notebook & Palmtop Computers.
2. Pen-Based Data System.
3. Portable Data Collection Terminals.
4. Personal Digital Assistants.
Negative Voltage Supply.
DESCRIPTION
The AIC1650 is a high performance inverting
DC/DC converter, designed to drive an external
power switch to generate programmable nega-
tive voltages. In the particularly suitable LCD
bias contrast application, maximum efficiency of
90% can be achieved with low cost PNP bipolar
transistor drivers. 4V to 20V input operation
range allows the AIC1650 to be powered di-
rectly by the battery pack in most battery-
operated applications for greater efficiency.
Output voltage can be scaled to -40V or greater
by two external resistors. A pulse frequency
modulation scheme is employed to maintain
high efficiency conversion under wide input
voltage range. Quiescent current is about
100
A and can be reduced to 8A in shutdown
mode. Switching frequency being around
100KHz to 320KHz range, small size switching
components are ideal for battery powered port-
able equipments, like notebook and palmtop
computers.
TYPICAL APPLICATION CIRCUIT
D1 1N5819
AIC1650
CL
DHI
DLOW
FB
GND
SHDN
VIN
VREF
C3
10nF
C4
0.047
F
*L
150
H
Q1
2N2907A
RB
1.5K~12K
R1
1M
C2
C1
V
IN
+4V ~ 20V
V
OUT
-12V~ -40V
5V
100
F
* Sumida
CD-54
SERIES
V
OUT
= -1.22V x R1/R2
100
F
+
+
R2
100K
Negative LCD Contrast Bias Power Supply
AIC1650
2
ORDERING INFORMATION
AIC1650 XX
PACKAGE TYPE
N: PLASTIC DIP
S: SMALL OUTLINE
TEMPERATURE RANGE
C=0
C~+70C
ORDER NUMBER
AIC1650CN
(PLASTIC DIP)
PIN CONFIGURATION
AIC1650CS
(PLASTIC SO)
TOP VIEW
DLOW
1
3
4
2
8
6
5
7
CL
VREF
SHDN
FB
DHI
GND
VIN
ABSOLUTE MAXIMUM RATINGS
Supply Voltage
.....................
..........................................................................
20V
SHDN Voltage
................................................................................................
15V
Operating Temperature Range
..............................................................
0
C~
70
C
Storage Temperature Range
..
........................................................
. -65
C~
150
C
TEST CIRCUIT
Refer to Typical Application Circuit.
ELECTRICAL CHARACTERISTICS
(V
IN
=13V, Ta=25
C, unless otherwise speci-
fied.)
PARAMETER
TEST CONDITIONS
MIN.
TYP.
MAX.
UNIT
Input Voltage
4
20
V
Switch Off Current
V
FB
= -50mV
100
200
A
V
REF
Voltage
I
SOURCE
= 250
A
1.16
1.22
1.28
V
V
REF
Source Current
250
A
DLOW "ON Resistance"
15
DHI "ON Resistance"
10
CL Threshold
50
70
90
mV
Shutdown Threshold
0.8
1.5
2.4
V
Shutdown Mode Current
V
SHDN
=0V
8
20
A
AIC1650
3
TYPICAL PERFORMANCE CHARACTERISTICS
(Ta=25
C)
V
IN
(V)
150
200
250
300
350
S
o
ur
c
e
C
u
r
r
e
nt
(
A)
V
REF
Source Current vs V
IN
4
8
12
20
16
V
IN
(V)
0
5
10
15
20
S
hut
dow
n
C
u
r
r
e
n
t
(
A)
Shutdown Current vs V
IN
4
6
8
10
12
14
16
18
20
V
IN
(V)
Dut
y
Cycle
(%)
Duty Cycle vs V
IN
Voltage
Ta=25
C
Ta=0
C
4
8
12
16
20
50
60
70
80
90
100
Ta=70
C
V
IN
(V)
F
r
equ
enc
y
(k
Hz
)
Frequency vs V
IN
Voltage
4
8
12
16
20
80
130
180
230
280
330
Ta=0
C
Ta=25
C
Ta=70
C
BLOCK DIAGRAM
+
-
+
-
ERROR COMPARATOR
LATCH
CURRENT LIMIT
COMPARATOR
1.22V
REFERENCE
VOLTAGE
PFM
OSCILLATOR
VREF
VIN
SHDN
4
3
2
1
FB
OUTPUT DRIVER
V
IN
V
IN
70mV
DHI
DLOW
CL
8
7
6
5
GND
AIC1650
4
PIN DESCRIPTIONS
PIN 1: VIN
- 4V to 20V input supply voltage.
PIN 2: VREF - 1.22V reference output. Bypass
with a 0.047
F capacitor to GND.
Sourcing capability is guaran-
teed to be greater than 250
A.
PIN 3: SHDN- Logic input to shutdown the chip.
>1.5V = normal operation,
GND = shutdown
In shutdown mode DLOW and
DHI pins are at high level.
PIN 4: FB
- Feedback signal input to sense
ground. Connecting a resistor
R1 to V
OUT
and a resistor R2 to
V
REF
pin yields the output volt-
age:
V
OUT
= -(R1/R2 ) x V
REF
PIN 5: GND - Power ground.
PIN 6: DLOW - Driver sinking output. Connected
to DHI when using an external
P-channel MOSFET. When us-
ing an external PNP bipolar
transistor, connect a resistor RB
from this pin to DHI. RB value
depends on V
IN
, inductor and
PNP bipolar transistor. By ad-
justing the RB value, efficiency
can be optimized.
PIN 7: DHI
- Driver sourcing output. Connect
to gate of the external P-channel
MOSFET or base of the PNP bi-
polar transistor.
PIN
8: CL
- Current-limit input. This pin
clamps the switch peak current
to prevent over-current damage
to the external switch.
APPLICATION INFORMATIONS
4
6
8
10
12
14
16
18
20
V
IN
(V)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Max. Output Power vs V
IN
M
a
x
.
O
u
tput
Pow
e
r (W
)
Typical Application Circuit
Inductor Value
100
H
270
H
120
H
150
H
180
H
220
H
300
H
330
H
The typical application circuit generates an adjustable
negative voltage for contrast bias of LCD displays.
Efficiency and output power can be optimized by us-
ing appropriate inductor and switch. The following
formulas provide a guideline for determining the op-
timal component values:
L
=
(11.1 0.15
V )
V
I
V
IN
IN
OUT OUT
-
PNP :
V
V
V
CEO IN
OUT
>
+
I
200
I
V
C,MAX
OUT
IN
V
0.4V at I
= 200
I
V
CE C
OUT
IN
<
and 10
=
RB
3 x L x (V
IN
- 0.8)
where, units: V
IN
& V
OUT
in V, I
OUT
in A, L in
H,
RB in
AIC1650
5
APPLICATION EXAMPLES
0
5
10
15
20
25
30
Load Current (mA)
75
80
85
90
95
Efficiency vs Load Current
V
OUT
= -15V
L
=220
H
V
IN
=13V
V
IN
=18V
Ef
fi
ci
e
n
cy (%
)
V
IN
=8V
4
6
8
10
12
14
16
18
20
V
IN
(V)
80
85
90
95
Efficiency vs V
IN
L=300
H
L=220
H
L=150
H
V
OUT
=-15V
I
OUT
=-10mA
E
ffi
ci
e
n
cy (%
)
0
5
10
15
20
25
30
Load Current (mA)
75
80
85
90
95
Efficiency vs Load Current
V
OUT
=-22V
L
=220
H
V
IN
=18V
V
IN
=13V
V
IN
=8V
Ef
fi
c
i
e
n
cy
(
%
)
V
IN
(V)
Efficiency vs V
IN
Ef
f
i
ci
e
n
cy (%
)
4
6
8
10
12
14
16
18
20
80
85
90
95
L=150
H
L=220
H
L=300
H
V
OUT
=-22V
I
OUT
=-10mA
0
5
10
15
20
25
30
Load Current (mA)
75
80
85
90
95
Efficiency vs Load Current
V
OUT
= -30V
L
= 220
H
V
IN
=18V
V
IN
=13V
V
IN
=8V
E
ffi
ci
e
n
cy (%)
V
IN
(V)
Efficiency vs V
IN
Ef
f
i
ci
e
n
cy (
%
)
4
6
8
10
12
14
16
18
20
80
85
90
95
L=300
H
L=220
H
L=150
H
V
OUT
= -30V
I
OUT
=
-10mA
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