ADP3607ARU-REEL Analog Devices Inc, ADP3607ARU-REEL Datasheet - Page 6

• Manufacturer Part Number: ADP3607ARU-REEL
• Manufacturer: Analog Devices Inc
• Type: Step Upr

Specifications of ADP3607ARU-REEL

• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (min): 3V
• Operating Supply Voltage (max): 5V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Package Type: TSSOP
• Pin Count: 8
• Mounting: Surface Mount
• Output Voltage: 3 to 9V
• Output Current: 50mA
• Lead Free Status / RoHS Status: Not Compliant

ADP3607
THEORY OF OPERATION
The ADP3607 uses a switched capacitor principle to generate
a regulated boost voltage from a positive input voltage. An
on-board oscillator generates a two-phase clock to control a
switching network that transfers charge between the storage
capacitors. The switches turn on and off at a 250 kHz rate that
is generated from an internal 500 kHz oscillator. The basic
principle behind the voltage conversion scheme is illustrated in
Figures 14 and 15.
Figure 14. ADP3607 Switch Configuration Charging the
Pump Capacitor
During phase one, S1 and S3 are ON, charging the pump ca-
pacitor to the input voltage. Before the next phase begins, S1
and S3 are turned OFF, as are S2 and S4 to prevent any over-
lap. S2 and S4 are turned ON during the second phase (see
Figure 15) and charge stored in the pump capacitor is trans-
ferred to the output capacitor.
During the second phase, the negative terminal of the pump
capacitor is connected to V
S4, and the positive terminal is connected to the output, result-
ing in a voltage shift at the output terminal. The ADP3607
block diagram is shown on the front page.
APPLICATION INFORMATION
Capacitor Selection
The ADP3607’s high internal oscillator frequency permits the
use of small capacitors for both the pump and the output ca-
pacitors. For a given load current, factors affecting the output
voltage performance are:
• Pump (C
• ESR of the C
Figure 15. ADP3607 Switch Configuration Charging the
Output Capacitor
0.01
1.0
0.1
10
–50
V
V
IN
IN
P
CERAMIC
ORGANIC SEMIC
TANTALUM
) and output (C
Figure 16. ESR vs. Temperature
ALUMINUM
P
S1
and C
S4
S1
S4
O
.
0
TEMPERATURE – C
C
C
IN
P
P
O
) capacitance.
through variable resistance switch
+
–
+
–
S3
S3
S2
S2
50
V
V
OUT
OUT
100
–6–
When selecting the capacitors, keep in mind that not all manu-
facturers guarantee capacitor ESR in the range required by the
circuit. In general, the capacitor’s ESR is inversely proportional
to its physical size, so larger capacitance values and higher volt-
age ratings tend to reduce ESR. Since the ESR is also a function
of the operating frequency, when selecting a capacitor make sure
its value is rated at the circuit’s operating frequency. Another
factor affecting capacitor performance is temperature.
Figure 16 illustrates the temperature effect on various capaci-
tors. If the circuit has to operate at temperatures significantly
different from +25 C, the capacitance and ESR values must be
carefully selected to adequately compensate for the change.
Various capacitor technologies offer improved performance over
temperature; for example, certain tantalum capacitors provide
good low temperature ESR but at a higher cost. Table II pro-
vides the ratings for different types of capacitor technologies to
help the designer select the right capacitors for the application.
The exact values of C
ESR capacitors such as solid tantalum and multilayer ceramic
capacitors are recommended to minimize voltage loss at high
currents. Table III shows a partial list of the recommended low
ESR capacitor manufacturers.
Input Capacitor
A small 1 F input bypass capacitor (preferably with low ESR)
such as tantalum or multilayer ceramic, is recommended to
reduce noise and supply transients, and supply part of the peak
input current drawn by the ADP3607. A large capacitor is rec-
ommended if the input supply is connected to the ADP3607
through long leads, or if the pulse current drawn by the device
might affect other circuitry through supply coupling.
Output Capacitor
The output capacitor (C
age when C
introduces steps in the V
pump charges C
ceramic or tantalum capacitors are recommended for C
minimize ripple on the output. Figure 17 illustrates the output
ripple voltage effect for various capacitance and ESR values.
Note that as the capacitor value increases beyond the point
where the dominant contribution to the output ripple is due to
the ESR, no significant reduction in V
added capacitance. Since output current is supplied solely by
Figure 17. Output Ripple Voltage (mV) vs. Capacitance
and ESR
40
35
30
25
20
15
10
5
0
P
is switched in parallel with C
20
O
, which contributes to V
IN
40
and C
O
OUT
) is alternately charged to the C
CAPACITANCE – F
waveform whenever the charge
60
O
are not critical. However, low
80
OUT
I
LOAD
OUT
100
O
ripple is achieved by
= 50mA
. The ESR of C
150m
100m
ADP3607-5
50m
ripple. Thus,
120
140
O
REV. 0
P
to
volt-
O