参数资料
型号: TPS60230RGTT
厂商: TEXAS INSTRUMENTS INC
元件分类: 稳压器
英文描述: 0.2 A SWITCHED CAPACITOR REGULATOR, 1250 kHz SWITCHING FREQ-MAX, PQCC16
封装: 3 X 3 MM, GREEN, PLASTIC, QFN-16
文件页数: 2/20页
文件大小: 640K
代理商: TPS60230RGTT
www.ti.com
UNDERVOLTAGE LOCKOUT
SHORT CIRCUIT AND OVERTEMPERTURE PROTECTION
OVERVOLTAGE PROTECTION AT VOUT
THEORY OF OPERATION/DESIGN PROCEDURE
Capacitor Selection
Power Efficiency
Power Dissipation
TPS60230
SLVS516A – MAY 2004 – REVISED JUNE 2004
The undervoltage lockout circuit shuts down the device when the voltage at VIN drops below a typical threshold
of 2.15 V. This prevents damage to the device. The UVLO circuit allows the device to start up again after the
voltage on the VIN pin has increased by about 100 mV above the UVLO lockout threshold.
The current at the VOUT pin is limited typically to 250 mA. When the junction temperature exceeds 155°C, the
device shuts down to protect the device from damage. After the temperature decreases to about 135°C, the
device starts up again if it is enabled.
The device uses the voltage at D1 to regulate voltage at VOUT. In case D1 is not connected, an overvoltage
protection circuit ensures that the output voltage at VOUT does not exceed its limits. The connection of the LEDs
must be started using D1 first. For all other LEDs there is no restriction in the sequence. For example, if there
are only 3 LEDs used, the first LED is connected to D1 and the other two LEDs can be connected to any other of
the D2 to D5 pins.
Ceramic capacitors such as X5R or X7R are recommended to be used with the TPS60230. For the two flying
capacitors C1 and C2, it is important to use low ESR capacitors to avoid unnecessary efficiency losses. Low
ESR capacitors on VOUT reduce the ripple voltage on the supply of the current sources. Table 2 lists capacitor
types that have been tested with the TPS60230.
Table 2. Capacitors
PART
VALUE
VOLTAGE
MANUFACTURER
SIZE
WEBSITE
C1608X5R1A105M
1
F
10 V
0603
C1608X5R1A474M
0.47
F
10 V
TDK
0603
www.componnent.tdk.com
C2012X7R1C105M
1
F
16 V
0805
LMK107BJ105MA
1
F
10 V
0603
LMK107BJ474MA
0.47
F
10 V
Taiyo Yuden
0603
www.t-yuden.com
LMK212BJ105MG
1
F
10 V
0805
The power conversion efficiency of the TPS60230 can be calculated by adding up the products of each LED
current and voltage and dividing it by the product of the input voltage and current. With a fully charged battery
where the input voltage is typically above the LED forward voltage, the charge pump operates in the 1x mode
and efficiency is very high. As the battery discharges, there is a point where the current sources no longer have
enough voltage overhead to maintain a constant current regulation. At that point, the charge pump switches into
the 1.5x mode. The conversion efficiency is lowest at the crossover. As the battery discharges further, the
efficiency again increases until at about 3.1 V where it reaches a second maximum. Below 3.1 V input voltage,
the maximum current per LED is less than 25 mA.
The maximum power dissipation inside the TPS60230 can be calculated based on the following equation:
PD max = [(1.5 × VI) – VO + 0.4 V] × IO
The maximum power dissipation occurs when the input voltage is just low enough to operate in 1.5x mode, with
a forward voltage of the white LED at maximum. This is typically for VI = 4.2 V and a forward voltage of 3.6 V.
This needs to be lower than the maximum allowed power dissipation of the package, which can be calculated
using the following equation:
10
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