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PDF PM8908 Data sheet ( Hoja de datos )
| Número de pieza | PM8908 | |
| Descripción | Monolithic buck converter | |
| Fabricantes | STMicroelectronics | |
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PM8908
Monolithic buck converter for DDR memory termination
Datasheet - production data
QFN20 3.5 x 4.0 mm
Applications
Memory termination regulator for DDR3, DDR4
and low power DDR3/DDR4
Notebook/desktop/server
Low voltage application for 1 V to 3.5 V input
rails
Features
Integrated MOSFETs for high efficiency
Current COT architecture
1 V to 3.5 V input voltage (VIN)
5.0 V supply voltage (VCC)
Constant frequency mode
1% output voltage accuracy
Two programmable switching frequencies
(0.6 MHz or 1 MHz)
ADJ output voltage from 0.5 V to 2 V
Embedded bootstrap diode
OV/UV/OC and overtemperature protection
Soft-off with integrated discharge resistor
External tracking
Power Good output
QFN20 3.5 x 4.0 mm compact package
Description
The PM8908 is a high efficiency monolithic step-
down switching regulator designed mainly for the
DDR termination.
The IC operates from 1 V to 3.5 V input voltage
(VIN).
The device uses a COT control loop that provides
very good performances in terms of load and line
transients. The current sense is internally
thermally compensated for optimum precision.
The output voltage is adjusted from 0.5 V to 2 V
with ± 1% accuracy overtemperature variations.
The PM8908 also provides external tracking
support.
The PM8908 provides positive and negative
overcurrent protection as well as
over/undervoltage and overtemperature
protection. PGOOD output easily provides real-
time information on the output voltage.
The PM8908 is available in a QFN20
3.5 x 4.0 mm package.
Order code
PM8908TR
Table 1. Device summary
Package
QFN20 (3.5 x 4.0 mm)
Packaging
Tape and reel
November 2015
This is information on a product in full production.
DocID027688 Rev 3
1/28
www.st.com
1 page  
PM8908
Typical application circuit and block diagram
1.2 Block diagram
EN
REFIN
VOUT
COMP
REF
GND
Figure 3. Block diagram
REFIN -16%
V OUT
Hy
Hy
PM8908 REFIN +16%
REFIN -30%
VOUT
UV
OV
SS REFIN +20%
PGOOD MODE
VCC
Delay
VCC UVLO
COT CONTROL
LOGIC,
PROTECTIONS
&
ADAPTIVE
DEAD TIMES
DEAD TIMES
VCC
Voltage
Reference
K
THERMAL
MONITOR
PHASE
PGND Discharge
CL
Current
Limit
VIN
BOOT
PHASE
PGND
DocID027688 Rev 3
5/28
28
5 Page 
PM8908
Electrical specifications
Symbol
Table 5. Electrical characteristics (continued)
Parameter
Test conditions
Min. Typ. Max. Unit
Soft-end
RDS Phase discharge resistance
Overcurrent protection
47
IOCL Positive overcurrent threshold LS sourcing, RM = 47 k
IOCLN Negative overcurrent threshold LS sourcing, RM = 47 k
Bootstrap switch
RBSS Boot switch on-resistance
IBOOT = 10 mA, TA = 25 °C
Over and undervoltage protection
4 7.6 11
-11 - 7.6 - 4
A
A
12
OVP OVP threshold
tOVPd OVP delay
UVP UVP threshold
tUVPd UVP delay
Undervoltage fault enable
delay
VOUT rising
Time from the VOUT pinout of + 20% of
REFIN to OVP fault
117
120
123
%
VREFIN
10 s
VOUT falling
Time from the VOUT pinout of -30% of
REFIN to UVP fault
65
68
71
%
VREFIN
256 s
Time from EN = H to undervoltage ready
2.4
ms
External tracking
Time from EN = H to undervoltage ready
9
ms
Overtemperature protection
OTP
Thermal shutdown threshold(1)
Thermal shutdown
hysteresis(1)
145 °C
10 °C
PGOOD
PGOOD
Upper threshold
Lower threshold
VPGOOD,L
PGOOD voltage low
impedance
IPGOOD,H
PGOOD leakage high
impedance
tPGd
tPGHd
tPGLd
PGOOD startup delay time
PGOOD high delay time
PGOOD low delay time
VOUT rising
Hysteresis
VOUT falling
Hysteresis
IPGOOD_SINK = 4 mA, VCC = 4.5 V
VPGOOD = 5.5 V
External tracking
Time from EN = H to PGOOD high
Rising edge
Falling edge(2)
116
8%
84 VREFIN
8
0.3 V
1 A
10 ms
0.8 1 1.2
10
ms
s
DocID027688 Rev 3
11/28
28
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet PM8908.PDF ] | |
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