General Description
The ultra-small MAX1719/MAX1720/MAX1721 monolithic,
CMOS charge-pump inverters accept input voltages
ranging from +1.5V to +5.5V. The MAX1720 operates at
12kHz, and the MAX1719/MAX1721 operate at 125kHz.
High efficiency, small external components, and logic-
controlled shutdown make these devices ideal for both
battery-powered and board-level voltage conversion
applications.
Oscillator control circuitry and four power MOSFET
switches are included on-chip. A typical MAX1719/
MAX1720/MAX1721 application is generating a -5V
supply from a +5V logic supply to power analog circuitry.
All three parts come in a 6-pin SOT23 package and can
deliver a continuous 25mA output current.
For pin-compatible SOT23 switched-capacitor voltage
inverters without shutdown (5-pin SOT23), see the
MAX828/MAX829 and MAX870/MAX871 data sheets. For
applications requiring more power, the MAX860/MAX861
deliver up to 50mA. For regulated outputs (up to -2 x VIN),
refer to the MAX868. The MAX860/MAX861 and MAX868
are available in space-saving µMAX packages.
Applications
Local Negative Supply from a Positive Supply
Small LCD Panels
GaAs PA Bias Supply
Handy-Terminals, PDAs
Battery-Operated Equipment
Features
♦♦1nA Logic-Controlled Shutdown
♦♦6-Pin SOT23 Package
♦♦99.9% Voltage Conversion Efficiency
♦♦50µA Quiescent Current (MAX1720)
♦♦+1.5V to +5.5V Input Voltage Range
♦♦25mA Output Current
♦♦Requires Only Two 1µF Capacitors
(MAX1719/MAX1721)
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
________________________________________________________________ Maxim Integrated Products 1
5
TOP VIEW
IN
GND
C1-
C1+
OUT
( ) ARE FOR MAX1719
SOT23-6
16
SHDN (SHDN)
MAX1719
MAX1720
MAX1721
2
34
Pin Configuration
C1+ C1-
IN
SHDN
OUT
GND
ON
1µF
1µF
OFF
INPUT
1.5V to 5.5V
NEGATIVE
OUTPUT
-1 ·VIN
25mA
MAX1721
Typical Operating Circuit
19-1439; Rev 2; 4/04
PART
MAX1719EUT -40°C to +85°C
TEMP RANGE PIN-
PACKAGE
6 SOT23-6
Ordering Information
SOT
TOP MARK
AACA
MAX1721EUT -40°C to +85°C 6 SOT23-6 AABT
MAX1720EUT -40°C to +85°C 6 SOT23-6 AABS
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
2_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = 10µF (MAX1720), C1 = C2 = 1µF
(MAX1719/MAX1721), circuit of Figure 1, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +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 to GND .................................................................-0.3V to +6V
OUT to GND .............................................................-6V to +0.3V
C1+, SHDN, SHDN to GND .........................-0.3V to (VIN + 0.3V)
C1- to GND...............................................(VOUT - 0.3V) to +0.3V
OUT Output Current..........................................................100mA
OUT Short Circuit to GND..............................................Indefinite
Continuous Power Dissipation (TA= +70°C)
6-Pin SOT23 (derate 8.7mW/°C above +70°C).................696mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
IOUT = 5mA
MAX1719/MAX1721
RL= 10kΩ
SHDN/ SHDN = GND
or VIN
VIN (MIN) ≤VIN ≤+2.5V
MAX1720
RL= 10kΩ
+2.5V ≤VIN ≤+5.5V
VIN (MIN) ≤VIN ≤+2.5V
+2.5V ≤VIN ≤+5.5V
IOUT = 0, TA= +25°C
SHDN = IN (MAX1719), SHDN = GND
(MAX1720/MAX1721), OUT is internally
forced to GND in shutdown
TA= +25°C
TA= +25°C
SHDN = IN (MAX1719),
SHDN = GND
(MAX1720/MAX1721)
IOUT = 10mA
CONDITIONS
80 µs
800
Wake-Up Time from Shutdown
10 nA
-100 0.05 100
IIL, IIH
SHDN/ SHDN Bias Current
0.2 V
0.6
VIL
SHDN/ SHDN Input Logic Low
VIN - 0.2 V
2.0
VIH
SHDN/ SHDN Input Logic High
Ω412RO, SHDN
OUT to GND
Shutdown Resistance
65 Ω
23 50
RO
Output Resistance (Note 1)
1.4 5.5
1.5 5.5 V
1.25 5.5
VIN
Supply Voltage Range
%
99 99.9Voltage Conversion Efficiency
70 125 180 kHz
71217
fOSC
Oscillator Frequency
0.02
1.5 5.5
µA
50 90
ICC
Quiescent Supply Current
(Note 3) 350 650
µA
0.001 1
ISHDN
Shutdown Supply Current
UNITSMIN TYP MAXSYMBOLPARAMETER
TA= 0°C to + 85°C
TA= +25°C
TA= 0°C to + 85°C
TA= +25°C
MAX1719/MAX1721
MAX1720
TA= +85°C
TA= +25°C
MAX1719/MAX1721
MAX1720
TA= 0°C to +85°C
TA= +25°C
TA= +85°C
TA= +25°C
MAX1719/MAX1721
MAX1720
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
_______________________________________________________________________________________ 3
-5
-4
-3
-2
-1
0
0202510 1553035404550
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1720/21toc01
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
VIN = +1.5V VIN = +2V
VIN = +3.3V
VIN = +5V
0
20
10
40
30
60
50
70
90
80
100
01015205253035 4540 50
MAX1720
EFFICIENCY vs. OUTPUT CURRENT
MAX1720/21toc02
OUTPUT CURRENT (mA)
EFFICIENCY (%)
VIN = +1.5V VIN = +3.3V
VIN = +2V
VIN = +5V
0
20
10
40
30
60
50
70
90
80
100
01015205253035 4540 50
MAX1719/MAX1721
EFFICIENCY vs. OUTPUT CURRENT
MAX1720/21toc03
OUTPUT CURRENT (mA)
EFFICIENCY (%)
VIN = +1.5V
VIN = +2V
VIN = +3.3V
VIN = +5V
Typical Operating Characteristics
(Circuit of Figure 1, VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = C3, TA= +25°C, unless other-
wise noted.)
ELECTRICAL CHARACTERISTICS
(VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = 10µF (MAX1720), C1 = C2 = 1µF
(MAX1719/MAX1721), circuit of Figure 1, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
VIN (MIN) ≤VIN ≤+2.5V
RL= 10kΩ
+2.5V ≤VIN ≤+5.5V
VIN (MIN) ≤VIN ≤+2.5V
+2.5V ≤VIN ≤+5.5V
IOUT = 0
SHDN = IN (MAX1719), SHDN = GND
(MAX1720/MAX1721), OUT is internally
forced to GND in shutdown
MAX1720
IOUT = 10mA
CONDITIONS
0.2 V
0.6
VIL
SHDN/ SHDN Input Logic Low
VIN - 0.2 V
2.1
VIH
SHDN/ SHDN Input Logic High
Ω12RO, SHDN
OUT to GND Shutdown
Resistance
65 ΩRO
Output Resistance (Note 1)
MAX1719/MAX1721
1.6 5.5MAX1719/MAX1721
1.5 5.5MAX1720
%
99Voltage Conversion Efficiency
60 200 kHz
621
fOSC
Oscillator Frequency
µA
100
ICC
Quiescent Current (Note 3) 750
UNITSMIN TYP MAXSYMBOLPARAMETER
VVIN
Supply Voltage Range
MAX1720
Note 1: Capacitor contribution (ESR component plus (1/fOSC) ·C) is approximately 20% of output impedance.
Note 2: All specifications from -40°C to +85°C are guaranteed by design, not production tested.
Note 3: The MAX1719/MAX1720/MAX1721 may draw high supply current during startup, up to the minimum operating supply voltage.
To guarantee proper startup, the input supply must be capable of delivering 90mA more than the maximum load current.
Continuous, long-term 25 mARMS
IOUT
Output Current
MAX1719/MAX1721
0
150
100
50
200
250
300
350
400
450
500
010515202530
MAX1720
OUTPUT VOLTAGE RIPPLE
vs. CAPACITANCE
MAX1720/21toc12
CAPACITANCE (µF)
OUTPUT VOLTAGE RIPPLE (mVp-p)
VIN = +4.75V, VOUT = -4.0V
VIN = +3.15V, VOUT = -2.5V
VIN = +1.9V, VOUT = -1.5V
0
10
5
20
15
30
25
35
02010 30 4052515 35 45 50
MAX1720
OUTPUT CURRENT vs. CAPACITANCE
MAX1720/21toc11
CAPACITANCE (µF)
OUTPUT CURRENT (mA)
VIN = +1.9V, VOUT = -1.5V
VIN = +3.15V, VOUT = -2.5V
VIN = +4.75V, VOUT = -4.0V
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
4_______________________________________________________________________________________
500µs/div
MAX1720
START-UP FROM SHUTDOWN
RL = 1kΩ
VOUT
2V/div
MAX1720/21toc10
VSHDN
5V/div
10
20
40
30
60
70
50
80
1.5 2.5 3.02.0 3.5 4.0 4.5 5.0 5.5
OUTPUT RESISTANCE
vs. INPUT VOLTAGE
MAX1720/21toc04
INPUT VOLTAGE (V)
OUTPUT RESISTANCE (Ω)
MAX1720
MAX1719/
MAX1721
10
30
20
50
40
60
70
-40 10-15 35 6085
OUTPUT RESISTANCE
vs. TEMPERATURE
MAX1720/21toc07
TEMPERATURE (°C)
OUTPUT RESISTANCE (Ω)
VIN = +2V
VIN = +1.5V
VIN = +3.3V
VIN = +5V
0
100
50
250
200
150
400
350
300
450
1.5 3.0 3.52.0 2.5 4.0 4.5 5.0 5.5
SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1720/21toc05
INPUT VOLTAGE (V)
SUPPLY CURRENT (µA)
MAX1720
MAX1719/
MAX1721
+85°C
+85°C
-40°C
-40°C
0
10
5
20
15
25
30
-40 10-15 35 60 85
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX1720/21toc06
TEMPERATURE (°C)
SHUTDOWN SUPPLY CURRENT (nA)
VIN = +5V
VIN = +3.3V
VIN = +1.5V
1000
10
-40 35 60-15 -10 85
PUMP FREQUENCY
vs. TEMPERATURE
100
MAX1720/21toc08
TEMPERATURE (°C)
FREQUENCY (kHz)
MAX1719/MAX1721
VIN = +5V
VIN = +1.5V MAX1720
VIN = +1.5V
VIN = +5V
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = C3, TA= +25°C, unless oth-
erwise noted.)
Detailed Description
The MAX1719/MAX1720/MAX1721 capacitive charge
pumps invert the voltage applied to their input. For high-
est performance, use low equivalent series resistance
(ESR) capacitors (e.g., ceramic).
During the first half-cycle, switches S2 and S4 open,
switches S1 and S3 close, and capacitor C1 charges to
the voltage at IN (Figure 2). During the second half-
cycle, S1 and S3 open, S2 and S4 close, and C1 is level
shifted downward by VIN volts. This connects C1 in par-
allel with the reservoir capacitor C2. If the voltage across
C2 is smaller than the voltage across C1, charge flows
from C1 to C2 until the voltage across C2 reaches
-VIN. The actual voltage at the output is more positive
than -VIN, since switches S1–S4 have resistance and the
load drains charge from C2.
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
_______________________________________________________________________________________ 5
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = C3, TA= +25°C, unless
otherwise noted.)
0
100
50
150
300
350
250
200
400
01.01.52.0 2.50.5 3.0 3.5 4.0 4.5 5.0
MAX1719/MAX1721
OUTPUT VOLTAGE RIPPLE vs. CAPACITANCE
MAX1720/21toc15
CAPACITANCE (µF)
OUTPUT VOLTAGE RIPPLE (mVp-p)
VIN = +4.75V, VOUT = -4.0V
VIN = +3.15V, VOUT = -2.5V
VIN = +1.9V, VOUT = -1.5V
50µs/div
MAX1721
START-UP FROM SHUTDOWN
RL = 1kΩ
VOUT
2V/div
MAX1720/21toc13
VSHDN
5V/div
Noninverting Shutdown Input. Drive this pin low for normal operation; drive it high for
shutdown mode. OUT is actively pulled to ground during shutdown.
SHDN5
GroundGND4
Negative Terminal of Flying CapacitorC1-3
Power-Supply Positive Voltage InputIN2
Inverting Charge-Pump OutputOUT
1
FUNCTIONNAME
0
10
5
20
15
30
25
35
MAX1719/MAX1721
OUTPUT CURRENT vs. CAPACITANCE
MAX1720/21toc14
CAPACITANCE (µF)
OUTPUT CURRENT (mA)
VIN = +1.9V, VOUT = -1.5V
VIN = +4.75V, VOUT = -4.0V
VIN = +3.15V, VOUT = -2.5V
01.01.5 2.0 2.50.5 3.0 3.5 4.0 4.5 5.0
Positive Terminal of Flying CapacitorC1+6
Pin Description
Inverting Shutdown Input. Drive this pin high for normal operation; drive it low for
shutdown mode. OUT is actively pulled to ground during shutdown.
SHDN
– 5
6
–
4
3
2
1
MAX1720
MAX1721
MAX1719
PIN
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
6_______________________________________________________________________________________
Charge-Pump Output
The MAX1719/MAX1720/MAX1721 are not voltage reg-
ulators: the charge pumps’ output resistance is
approximately 23Ωat room temperature (with VIN =
+5V), and VOUT approaches -5V when lightly loaded.
VOUT will droop toward GND as load current increases.
The droop of the negative supply (VDROOP-) equals the
current draw from OUT (IOUT) times the negative con-
verter’s output resistance (RO):
VDROOP- = IOUT x RO
The negative output voltage will be:
VOUT = -(VIN - VDROOP-)
Efficiency Considerations
The efficiency of the MAX1719/MAX1720/MAX1721 is
dominated by its quiescent supply current (IQ) at low
output current and by its output impedance (ROUT) at
higher output current; it is given by:
where the output impedance is roughly approximated
by:
The first term is the effective resistance of an ideal
switched-capacitor circuit (Figures 3a and 3b), and
RSW is the sum of the charge pump’s internal switch
resistances (typically 8Ωto 9Ωat VIN = +5V). The typi-
cal output impedance is more accurately determined
from the Typical Operating Characteristics.
Shutdown Mode
The MAX1719/MAX1720/MAX1721 have a logic-con-
trolled shutdown input. Driving SHDN low places the
MAX1720/MAX1721 in a low-power shutdown mode.
The MAX1719’s shutdown input is inverted from that of
the MAX1720/MAX1721. Driving SHDN high places the
MAX1719 in a low-power shutdown mode. The charge-
pump switching halts, supply current is reduced to
1nA, and OUT is actively pulled to ground through a 4Ω
resistance.
Applications Information
Capacitor Selection
To maintain the lowest output resistance, use capaci-
tors with low ESR (Table 1). The charge-pump output
resistance is a function of C1’s and C2’s ESR.
Therefore, minimizing the charge-pump capacitor’s
ESR minimizes the total output resistance. Table 2
gives suggested capacitor values for minimizing output
resistance or minimizing capacitor size.
R1
fC1
2R 4ESR ESR
OUT OSC SW C1 C2
≅
()
×++ +
η≅ +−×
I
II
IR
V
OUT
OUT Q
OUT OUT
IN
1
S1
IN
S2
S3 S4
C1
C2
VOUT = -(VIN)
Figure 2. Ideal Voltage Inverter
V+
C1
f
C2 RL
VOUT
Figure 3a. Switched-Capacitor Model
REQUIV =
REQUIV
VOUT
RL
1
V+
f × C1 C2
Figure 3b. Equivalent Circuit
NOTE: ( ) CAPACITORS ARE FOR MAX1720.
*ON/OFF POLARITY OF SHDN IS REVERSED FOR MAX1719.
C1
1µF (10µF)
C2
1µF (10µF)
21
5
ON
OFF
3
RL
6
4
C3
1µF (10µF)
C1+ C1-
IN
SHDN
OUT
GND
INPUT
1.5V to 5.5V NEGATIVE
OUTPUT
-1 ·VIN
25mA
MAX1719*
MAX1721
Figure 1. Typical Application Circuit
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
_______________________________________________________________________________________ 7
Surface-Mount
Tantalum
PRODUCTION
METHOD
714-969-2491
803-946-0690
PHONE
603-224-1961 603-224-1430
714-960-6492
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FAXMANUFACTURER
AVX
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Matsuo 714-960-6492
803-626-3123X7R
X7R
Surface-Mount
Ceramic
Table 2. Capacitor Selection for Minimum Output Resistance or Capacitor Size
Table 1. Low-ESR Capacitor Manufacturers
fOSC
CAPACITORS TO MINIMIZE SIZE
(RO= 40Ω, TYP)
C1 = C2
0.33µF
3.3µF12kHz
CAPACITORS TO MINIMIZE
OUTPUT RESISTANCE
(RO= 23Ω, TYP)
C1 = C2
125kHz
10µF
1µF
MAX1720
PART
MAX1719/MAX1721
Flying Capacitor (C1)
Increasing the flying capacitor’s value reduces the out-
put resistance. Above a certain point, increasing C1’s
capacitance has a negligible effect because the output
resistance becomes dominated by the internal switch
resistance and capacitor ESR.
Output Capacitor (C2)
Increasing the output capacitor’s value reduces the
output ripple voltage. Decreasing its ESR reduces both
output resistance and ripple. Lower capacitance values
can be used with light loads if higher output ripple can
be tolerated. Use the following equation to calculate the
peak-to-peak ripple:
Input Bypass Capacitor (C3)
Bypass the incoming supply to reduce its AC impedance
and the impact of the MAX1719/MAX1720/MAX1721’s
switching noise. A bypass capacitor with a value equal
to that of C1 is recommended.
Voltage Inverter
The most common application for these devices is a
charge-pump voltage inverter (Figure 1). This applica-
tion requires only two external components—capacitors
C1 and C2—plus a bypass capacitor, if necessary.
Refer to the Capacitor Selection section for suggested
capacitor types.
Cascading Devices
Two devices can be cascaded to produce an even
larger negative voltage (Figure 4). The unloaded output
voltage is normally -2 x VIN, but this is reduced slightly
by the output resistance of the first device multiplied by
the quiescent current of the second. When cascading
more than two devices, the output resistance rises dra-
matically. For applications requiring larger negative
voltages, see the MAX865 and MAX868 data sheets.
The maximum load current and startup current of the
nth cascaded circuit must not exceed the maximum
output current capability of the (n - 1)th circuit to ensure
proper startup.
V=
I
2 f C2 2 I ESR
RIPPLE OUT
OSC OUT C2
××
+× ×
MAX1719
MAX1720
MAX1721
“n”
MAX1719
MAX1720
MAX1721
“1”
2
1VOUT
C2
2
+VIN
C1
C2
SHDN (MAX1719)
SHDN (MAX1720/
MAX1721)
C1
33
44
6
55
61
VOUT = -nVIN
…
…
Figure 4. Cascading MAX1719s or MAX1720s or MAX1721s
to Increase Output Voltage
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
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_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
©2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Paralleling Devices
Paralleling multiple MAX1719s, MAX1720s, or
MAX1721s reduces the output resistance. Each device
requires its own pump capacitor (C1), but the reservoir
capacitor (C2) serves all devices (Figure 5). Increase
C2’s value by a factor of n, where n is the number of
parallel devices. Figure 5 shows the equation for calcu-
lating output resistance.
Combined Doubler/Inverter
In the circuit of Figure 6, capacitors C1 and C2 form the
inverter, while C3 and C4 form the doubler. C1 and C3
are the pump capacitors; C2 and C4 are the reservoir
capacitors. Because both the inverter and doubler use
part of the charge-pump circuit, loading either output
causes both outputs to decline toward GND. Make sure
the sum of the currents drawn from the two outputs
does not exceed 25mA.
Heavy Load Connected to a
Positive Supply
Under heavy loads, where a higher supply is sourcing
current into OUT, the OUT supply must not be pulled
above ground. Applications that sink heavy current into
OUT require a Schottky diode (1N5817) between GND
and OUT, with the anode connected to OUT (Figure 7).
Layout and Grounding
Good layout is important, primarily for good noise per-
formance. To ensure good layout, mount all compo-
nents as close together as possible, keep traces short
to minimize parasitic inductance and capacitance, and
use a ground plane.
MAX1719
MAX1720
MAX1721
2
5
1
VOUT = (2VIN) -
(VFD1) - (VFD2)
C2
+VIN
C1
3
4
6VOUT = -VIN
C4
D1
D1, D2 = 1N4148
C3
D2
SHDN (MAX1719)
SHDN (MAX1720)
(MAX1721)
Figure 6. Combined Doubler and Inverter
MAX1719
MAX1720
MAX1721
4
1
GND
OUT
V+
RL
Figure 7. Heavy Load Connected to a Positive Supply
TRANSISTOR COUNT: 85
MAX1719
MAX1720
MAX1721
“n”
MAX1719
MAX1720
MAX1721
“1”
2
1VOUT
C2
2
+VIN
C1
C1
33
44
6
55
61
VOUT = -VIN
RO = RO OF SINGLE DEVICE
NUMBER OF DEVICES
…
…
SHDN (MAX1719)
SHDN (MAX1720/
MAX1721)
Figure 5. Paralleling MAX1719s or MAX1720s or MAX1721s to
Reduce Output Resistance
Chip Information