ADP3604

REV. 0

–6–

The output current is supplied solely by the output capacitor

C3 during one-half of the charge-pump cycle. This introduces a

peak-to-peak ripple of:

2

×120 kHz ×C3

+ I

For a nominal F pump of 120 kHz (one-half the nominal 240 kHz

oscillator frequency) and C3 = 10

µF with an ESR of 0.15 Ω,

ripple voltage is approximately 60 mV with a 120 mA load

current.

Multilayer Ceramic Capacitors (MLCC) offer great perfor-

mance and small size. Using multiple capacitors connected in

parallel yields lower ESR and a potential saving in cost. Lighter

loads require proportionally smaller capacitors. To reduce high

frequency noise, bypass the output with a 0.1

µF ceramic

capacitor.

ADP3604

8

7

3

C2

4.7µF

1

4

C3

4.7µF

2

5

SENSE

INPUT

L1

10µH

C4

4.7µF

C1

4.7µF

Figure 17. Circuit with Improved Output Ripple & Noise

Voltage

Table III. Recommended Components for Circuit in Figure 17

Component

Manufacturer/Type

C2

Sprague, 293D475X0035D2W

C1, C3, C4

TOKIN, 1E475ZY5U-C205-F

L1

Coiltronics, CTX32CT

EXTERNAL INPUT FILTERING

If the ADP3604 is supplied from an high-impedance source,

connect an additional bypass capacitor from V+ to ground.

Low-ESR capacitors of up to 100

µF give best results. Place

external capacitors close to the supply pins of the device with

the ground connection made as close to the device ground as

possible. The same ground point should be used for the output

bypass capacitor.

Smaller bypass capacitors can be used in conjunction with a

π-LC filter.

ADP3604

8

7

3

C3

4.7µF

1

4

C4

4.7µF

2

5

SENSE

INPUT

L2

10µH

C5

4.7µF

C2

4.7µF

L1

1µH

C1

4.7µF

Figure 18. Circuit with Reduced Input and Output Ripple

& Noise Voltage

Table IV. Recommended Components for Circuit in Figure 18

Component

Manufacturer/Type

C3

Sprague, 293D475X0035D2W

C1, C2, C4, C5

TOKIN, 1E475ZY5UC205F

L1

Coiltronics, CTX32CT-1R0

L2

Coiltronics, CTX32CT-100

SHUTDOWN MODE

ADP3604’s output can be turned off by utilizing the shutdown

pin, Pin 4. Pulling the shutdown pin high to a TTL/CMOS

logic compatible level will stop the internal oscillator and turn

OFF the output pass transistor. A digital low level will turn the

output ON. If the shutdown feature of the device is not used,

Pin 4 should be tied to the ground pin of the device.

MAXIMUM OUTPUT VOLTAGE

Maximum unregulated output voltage can be obtained by con-

shown in Figure 19.

Under this condition, the magnitude of the unregulated output

tional to the load current as shown on the graph in Figure 19.

LOAD CURRENT – mA

–5.0

–4.0

10

90

30

50

70

–3.0

ADP3604

8

7

3

1

4

2

5

Figure 19. Maximum Unregulated Output Voltage

The output voltage is approximated using the following formula:

Ωs.

LOAD CURRENT – mA

–5.0

–4.0

10

90

30

50

70

–3.0

ADP3604

8

7

3

1

4

2

5

R

R = 10k

R = 5k

110

Figure 20. Maximum Regulated Output Voltage