
4.1.15 CP
4.1.16 USB LDO Short-Circuit Protection Scheme
TPS65950
Integrated Power Management/Audio Codec
SWCS032 – OCTOBER 2008
www.ti.com
Table 4-15. Output Load Conditions (continued)
Regulator
Parameter
Test Conditions
Min(1)
Typ(2)
Max(3)
Unit
VRUSB_1V5 LDO Filtering capacitor
Connected from VINTUSB1P5 to GND
0.3
1
2.7
F
Filtering capacitor ESR
0
10
600
m
The CP generates a 4.8-V (nominal) power supply voltage from the battery to the VBUS pin. The input
voltage range is 2.7 to 4.5 V for the battery voltage. The CP operating frequency is 1 MHz.
The CP tolerates 7 V on VBUS when it is in power-down mode. The CP integrates a short-circuit current
limitation at 450 mA.
Table 4-16 lists the characteristics of the CP.
Table 4-16. CP Characteristics
Parameter
Test Conditions
Min(1)
Typ(2) Max(3)
Unit
Output Load Conditions
Filtering capacitor
Connected from VBUS to VSSP
1.41
4.7
6.5
F
Flying capacitor
Connected from CP to CN
1.32
2.2
3.08
F
Filtering capacitor ESR
20
m
Electrical Characteristics
VIN
Input voltage
On mode: VIN = VBAT
2.7
3.6
4.5
V
VO
Output voltage
4.6
4.8
5.25
V
VBAT > 3 V at VBUS
0
100
Iload
Rated output current
mA
2.7 V < VBAT < 3 V, at VBUS
0
50
Efficiency
ILoad = 100 mA, VBAT = 3.6 V
55%
Setting time
ILOADmax/2 to ILOAmax in 5 s
100
400
s
Startup time
3
ms
Short-circuit limitation current
250
350
450
mA
Dc load regulation
ILOADmin to ILOADmax
250
500
mV
3.0 V to VBATmax
Dc line regulation
250
350
mV
ILoad = 100 mA
IVBUS_5Vmax/2 – IVBUS_5Vmax
300
350
50
s, C = 2*4.7 F
Transient load regulation
mV
0 – IVBUS_5Vmax/2, 50 s, C = 2*4.7 F
350
Transient line regulation
VBATmin to VBATmax in 50 s, C = 2*4.7 F
300
350
mV
(1)
Min = Minimum value
(2)
Typ = Typical value
(3)
Max = Maximum value
The short-circuit current for the LDOs and dc-dc converters in TPS65950 is approximately twice the
maximum load current. In certain cases when the output of the block is shorted to ground, the power
dissipation can exceed the 1.2-W requirement if no action is taken. A short-circuit protection scheme is
included in the TPS65950 to ensure that if the output of an LDO or dc-dc is short-circuited, the power
dissipation does not exceed the 1.2-W level.
The three USB LDOs, VRUSB3V1, VRUSB1V8, and VRUSB1V5, are included in this short-circuit
protection scheme, which monitors the LDO output voltage at a frequency of 1 Hz and generates an
interrupt (sc_it) when a short circuit is detected.
The scheme compares the LDO output voltage to a reference voltage and detects a short circuit if the
LDO voltage drops below this reference value (0.5 or 0.75 V programmable). In the case of the
VRUSB3V1 and VRUSB1V8 LDOs, the reference is compared with a divided-down voltage (1.5 V typical).
If a short circuit is detected on VRUSB3V1, the power subchip FSM switches this LDO to sleep mode.
Power Module
56