PM6644 Datasheet PDF - STMicroelectronics

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PM6644
STMicroelectronics

Part Number PM6644
Description 350mA adjustable step-down regulator
Page 30 Pages


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PM6644
350 mA adjustable step-down regulator
Datasheet production data
Features
4.5 V to 25 V input voltage range
Output voltage VOUT: fixed 3.47 V or adjustable
0.9 V to 8 V
350 mA valley current limit
Constant-on-time control
Programmable switching frequency
Pulse skipping mode (skip mode) at light loads
Independent EN signals
Latched OVP and UVP
DFN10
switching regulator can be programmed to
regulate a fixed value of 3.47 V or it can deliver an
adjustable voltage, depending on the FB pin set-
up.
Applications
Networking power supply
Portable applications
Microcontroller supply
Industrial supply
Description
The PM6644 is a 350 mA valley current limit step-
down regulator capable of delivering an
adjustable output voltage in the range between
0.9 V and 8 V. A fixed value of output voltage is
also available (3.47 V), saving the external
resistor divider. It is housed in a small DFN10 3x3
package. The switching regulator is based on
COT (constant-on-time) architecture, that assures
fast load transient response; the embedded
voltage feed-forward provides nearly constant
switching frequency operation. The pulse skipping
technique increases efficiency at very light load.
The switching frequency can be adjusted from
200 kHz to 600 kHz through a simple resistor. The
Table 1. Device summary
Part number
Package
PM6644
PM6644TR
DFN10
DFN10
Packing
Tube
Tape and reel
June 2012
This is information on a product in full production.
Doc ID 023203 Rev 1
1/35
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Contents
Contents
PM6644
1 Simplified application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4 Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.6 Typical operating characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2 Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.1 Switching regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.1.1 Output voltage set-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.1.2 Constant-on-time control (COT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.1.3 PWM control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.1.4 Skip mode management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.1.5 Current sensing and current limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.1.6 Soft-start and soft-end . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1.7 Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1.8 Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1.9 Undervoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1.10 VCC undervoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1.11 VCC and BYP power management . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.1.12 3.3 V linear regulator section (REF3) . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.1.13 General fault management: thermal protection . . . . . . . . . . . . . . . . . . . 20
3 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.1 External component selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.1.1 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.1.2 Input capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.1.3 Output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.1.4 Maximum RMS output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4 Typical application configuration VOUT = 8 V . . . . . . . . . . . . . . . . . . . . 25
4.1 Test set configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
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PM6644
Contents
4.2 Characterization report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.3 Efficiency vs. load (VIN = 12 V, VOUT = 8 V) . . . . . . . . . . . . . . . . . . . . . . . 27
5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
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List of tables
List of tables
PM6644
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Frequency configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Fault management summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
VCC and BYP management (EN pin > 2 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Inductor part number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Input capacitor part numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Output capacitor part number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
DFN10 (3x3 mm) mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
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