ADM660ARZ Analog Devices Inc, ADM660ARZ Datasheet - Page 8

• Manufacturer Part Number: ADM660ARZ
• Description: IC CONVERTER SWITCH CAP 8SOIC
• Manufacturer: Analog Devices Inc
• Type: Step-Up (Boost), Switched Capacitor (Charge Pump), Doubler, Invertingr

Specifications of ADM660ARZ

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: -1.5 ~ -7 V, 3 ~ 14 V
• Current - Output: 100mA
• Voltage - Input: 1.5 ~ 7 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Power - Output: 450mW
• Primary Input Voltage: 7V
• No. Of Outputs: 1
• Output Voltage: 15V
• Output Current: 100mA
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +85°C
• Msl: MSL 1 - Unlimited
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency - Switching: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

ADM660/ADM8660
Inverting Negative Voltage Generator
Figures 5 and 6 show the ADM660/ADM8660 configured to
generate a negative output voltage. Input supply voltages from
1.5 V up to 7 V are allowable. For supply voltage less than 3 V,
LV must be connected to GND. This bypasses the internal
regulator circuitry and gives best performance in low voltage
applications. With supply voltages greater than 3 V, LV may
be either connected to GND or left open. Leaving it open facili-
tates direct substitution for the ICL7660.
OSCILLATOR FREQUENCY
The internal charge-pump frequency may be selected to be
either 25 kHz or 120 kHz using the Frequency Control (FC)
input. With FC unconnected (ADM660) or connected to GND
(ADM8660), the internal charge pump runs at 25 kHz while, if
FC is connected to V+, the frequency is increased by a factor of
five. Increasing the frequency allows smaller capacitors to be
used for equivalent performance or, if the capacitor size is un-
changed, it results in lower output impedance and ripple.
If a charge-pump frequency other than the two fixed values is
desired, this is made possible by the OSC input, which can
either have a capacitor connected to it or be overdriven by an
external clock. Refer to the Typical Performance Characteris-
tics, which shows the variation in charge-pump frequency versus
capacitor size. The charge-pump frequency is one-half the oscil-
lator frequency applied to the OSC pin.
If an external clock is used to overdrive the oscillator, its levels
should swing to within 100 mV of V+ and GND. A CMOS
driver is, therefore, suitable. When OSC is overdriven, FC has
no effect but LV must be grounded.
Note that overdriving is permitted only in the voltage inverter
configuration.
FC
Open
V+
Open or V+
Open
Figure 6. ADM8660 Voltage Inverter Configuration
Table I. ADM660 Charge-Pump Frequency Selection
Figure 5. ADM660 Voltage Inverter Configuration
SHUTDOWN
10 F
10 F
CONTROL
C1
C1
+
+
OSC
Open
Open
Ext Cap
Ext CLK
FC
CAP+
GND
CAP–
FC
CAP+
GND
CAP–
SD
ADM660
ADM8660
Charge Pump
25 kHz
120 kHz
See Typical Characteristics
Ext CLK Frequency/2
OSC
OUT
OUT
V+
LV
V+
LV
+1.5V TO +7V
+1.5V TO +7V
INPUT
+
INPUT
+
C2
10 F
C2
10 F
INVERTED
NEGATIVE
OUTPUT
INVERTED
NEGATIVE
OUTPUT
C1, C2
10 µF
2.2 µF
–8–
FC
GND
V+
GND or V+ Ext Cap
GND
Voltage Doubling Configuration
Figure 8 shows the ADM660 configured to generate increased
output voltages. As in the inverting mode, only two external
capacitors are required. The doubling function is achieved by
reversing some connections to the device. The input voltage is
applied to the GND pin and V+ is used as the output. Input
voltages from 2.5 V to 7 V are allowable. In this configuration,
pins LV, OUT must be connected to GND.
The unloaded output voltage in this configuration is 2 (V
Output resistance and ripple are similar to the voltage inverting
configuration.
Note that the ADM8660 cannot be used in the voltage
doubling configuration.
Shutdown Input
The ADM8660 contains a shutdown input that can be used to
disable the device and thus reduce the power consumption. A
logic high level on the SD input shuts the device down reducing
the quiescent current to 0.3 µA. During shutdown, the output
voltage goes to 0 V. Therefore, ground referenced loads are not
powered during this state. When exiting shutdown, it takes
several cycles (approximately 500 µs) for the charge pump to
reach its final value. If the shutdown function is not being used,
then SD should be hardwired to GND.
Capacitor Selection
The optimum capacitor value selection depends the charge-pump
frequency. With 25 kHz selected, 10 µF capacitors are recommended,
while with 120 kHz selected, 2.2 µF capacitors may be used.
Other frequencies allow other capacitor values to be used. For
maximum efficiency in all cases, it is recommended that capaci-
tors with low ESR are used for the charge-pump. Low ESR
capacitors give both the lowest output resistance and lowest
ripple voltage. High output resistance degrades the overall power
efficiency and causes voltage drops, especially at high output
Table II. ADM8660 Charge-Pump Frequency Selection
TO +7V
INPUT
+2.5V
Figure 7. ADM660/ADM8660 External Oscillator
C1
+
Figure 8. Voltage Doubler Configuration
+
OSC
Open
Open
Ext CLK
10 F
FC
CAP+
GND
CAP–
ADM8660
ADM660
FC
CAP+
GND
CAP–
Charge Pump
25 kHz
120 kHz
See Typical Characteristics
Ext CLK Frequency/2
ADM660
OSC
OUT
LV
V+
+1.5V TO +7V
OSC
OUT
V+
LV
INPUT
+
C2
CMOS GATE
+
10 F
CLK OSC
INVERTED
NEGATIVE
OUTPUT
DOUBLED
POSITIVE
OUTPUT
REV. B
C1, C2
10 µF
2.2 µF
IN
).