TPS54200/TPS54201は1.5Aの同期整流降圧型単色/IRドライバで、最大入力電圧は28Vです。電流モード動作により、高速な過渡応答が得られ、ループを簡単に安定化できます。
TPS54200/TPS54201を使用することで、暗視カメラのように、シングル・ストリングまたはマルチストリングの単色/赤外線(IR) LEDアレイを駆動できます。
TPS54200/TPS54201はMOSFETを内蔵し、SOT-23-THINパッケージを採用しているため、高い電力密度を実現し、PCB上でわずかな面積しか占有しません。
TPS54200/TPS54201にはアナログ調光モードが実装されており、このモードではPWM信号入力のデューティ・サイクルに比例して内部基準電圧を変化させ、調光を行います。また、PWM調光モードもサポートしており、このモードでは内部基準電圧が100mVに半減して、より高い効率を実現します。
型番 | パッケージ | 本体サイズ(公称) |
---|---|---|
TPS54200 | SOT-23-THIN (6) | 1.6mm×2.9mm |
TPS54201 | SOT-23-THIN (6) | 1.6mm×2.9mm |
Changes from A Revision (March 2017) to B Revision
Changes from * Revision (November 2016) to A Revision
PIN | TYPE(1) | DESCRIPTION | |
---|---|---|---|
NAME | NO. | ||
BOOT | 6 | O | A bootstrap capacitor is required between BOOT and SW. |
FB | 4 | I | LED current-detection feedback |
GND | 1 | G | Power ground |
PWM | 5 | I | Dimming input. Default low (internally pulled low). In analog dimming mode, the internal reference is proportional to the PWM input duty cycle. In PWM dimming mode, LED current is ON during the PWM high period in each PWM cycle. |
SW | 2 | O | Switching node to the external inductor |
VIN | 3 | P | Input supply voltage |
VALUE | UNIT | |||
---|---|---|---|---|
V(ESD) | Electrostatic discharge | Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) | ±4000 | V |
Charged-device model (CDM), per JEDEC specification JESD22-C101(2) | ±1500 |
THERMAL METRIC(1) | TPS5420x | UNIT | |
---|---|---|---|
DDC (SOT-23-THIN) | |||
6 PINS | |||
RθJA | Junction-to-ambient thermal resistance | 89.2 | °C/W |
RθJC(top) | Junction-to-case (top) thermal resistance | 39.5 | °C/W |
RθJB | Junction-to-board thermal resistance | 14.7 | °C/W |
ψJT | Junction-to-top characterization parameter | 1.2 | °C/W |
ψJB | Junction-to-board characterization parameter | 14.7 | °C/W |
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT | |
---|---|---|---|---|---|---|
INPUT SUPPLY | ||||||
VVIN | Input voltage range | 4.5 | 28 | V | ||
IOFF | Shutdown current | PWM = GND | 2 | 8.6 | µA | |
VVIN_UVLO | VIN undervoltage lockout | Rising VVIN | 3.83 | 4.2 | 4.47 | V |
Falling VVIN | 3.4 | 3.7 | 3.95 | |||
Hysteresis | 470 | mV | ||||
DIMMING (PWM PIN) | ||||||
VADIM | Analog dimming-mode threshold | Rising VPWM | 1.97 | 2.07 | 2.17 | V |
Falling VPWM | 1.8 | |||||
VPDIM | PWM dimming-mode threshold | Rising VPWM | 0.9 | 1 | 1.1 | V |
Falling VPWM | 0.8 | |||||
VPWM | Threshold to identify PWM duty cycle | Rising VPWM | 0.91 | 1 | 1.12 | V |
Falling VPWM | 0.5 | 0.63 | 0.72 | |||
VPWM_SHUTDOWN | Shutdown threshold | 0.35 | 0.55 | V | ||
FEEDBACK AND ERROR AMPLIFIER | ||||||
VFB1 | Feedback voltage in analog dimming mode | PWM = 3.3 V, SW duty cycle > 90% | 201 | 205 | 210 | mV |
VFB2 | Feedback voltage in PWM dimming mode | PWM = 1.5 V, SW duty cycle > 90% | 96 | 100 | 104 | mV |
BOOT PIN | ||||||
VBOOT_UVLO | BOOT-SW UVLO threshold | Rising | 2.1 | 2.33 | V | |
Falling | 2 | 2.2 | ||||
POWER STAGE | ||||||
RHSD | High-side FET on-resistance | VBOOT – VSW= 6 V | 150 | 259 | mΩ | |
RLSD | Low-side FET on-resistance | VVIN > 6 V | 70 | 120 | mΩ | |
CURRENT LIMIT | ||||||
ILIM_HS1 | High-side current limit 1 | Either one of the following conditions:
1. PWM dimming mode 2. Analog dimming mode and PWM duty cycle >25% |
2.4 | 3 | 3.6 | A |
ILIM_HS2 | High-side current limit 2 | Analog dimming mode and PWM duty cycle <25% | 1 | 1.4 | 1.8 | A |
ILIM_LS_SOURCE | Low-side source current limit | VVIN > 6 V | 2.3 | 3.3 | 4.4 | A |
ILIM_LS_SINK | Low-side sink current limit | VVIN > 6 V | 1.25 | 1.7 | 2.2 | A |
FAULT PROTECTION | ||||||
Thermal shutdown(1) | Rising temperature | 150 | 160 | 170 | °C | |
Hysteresis | 10 | °C | ||||
VOVP | Overvoltage protection | 1 | V | |||
VOCP | Overcurrent protection | 120% |
The TPS5420x device is a 1.5-A synchronous buck LED driver up to 28-V input. Current-mode operation provides fast transient response. The optimized internal compensation network minimizes the external component count and simplifies the control loop design.
The TPS5420x device has a fixed 600-kHz switching frequency for a good tradeoff between efficiency and size.
The integrated 150-mΩ high-side MOSFET and 70-mΩ low-side MOSFET allow for a high-efficiency LED driver with continuous output current up to 1.5 A.
The TPS5420x device supports deep dimming in both analog and PWM dimming modes. In analog dimming mode, the internal reference voltage is changed in proportion to the duty cycle of the PWM signal in the 1% to 100% range. In the PWM dimming mode, the LED turns on and off periodically according to the PWM duty cycle. For higher efficiency, the internal reference is halved to 100 mV.
Cycle-by-cycle current limit in the high-side MOSFET protects the converter in overload conditions and is enhanced by a low-side MOSFET freewheeling current limit which prevents current runaway. There is a low-side MOSFET sinking-current limit to prevent excessive reverse current.
For safety and protection, the TPS5420x includes LED-open and -short protection, sense-resistor-open and -short protection, and device thermal protection. The TPS54200 device implements shutdown-and-latch mode protection, whereas the TPS54201 device implements auto-retry mode protection.
The device uses a fixed-frequency and peak-current-mode control. The LED current is sensed by a resistor in series with the LED string. The sensed voltage is fed to the FB pin through an RC filter, and then compared to an internal voltage reference by an error amplifier. An internal oscillator initiates the turnon of the high-side power switch. The error amplifier output is compared to the current of the high-side power switch. When the power-switch current reaches the error-amplifier output-voltage level, the high-side power switch is turned off and the low-side power switch is turned on. Thus, the error amplifier output voltage regulates inductor peak current, and in turn the LED current, to a target value. The device implements a current limit by clamping the error amplifier voltage to a maximum level and also implements a minimum clamp for improved transient-response performance.
The device has a transconductance amplifier as the error amplifier. The error amplifier compares the FB voltage to the lower of the internal soft-start voltage or the internal voltage reference. The transconductance of the error amplifier is 240 μA/V typically. The frequency compensation components are placed internally between the output of the error amplifier and ground.
The device adds a compensating ramp to the signal of the switch current. This slope compensation prevents subharmonic oscillations as the duty cycle increases. The available peak inductor current remains constant over the full duty-cycle range.
The device implements internal undervoltage-lockout (UVLO) circuitry on the VIN pin. The device is disabled when the VIN pin voltage falls below the internal VIN UVLO threshold, which is 3.7 V typical. The internal VIN UVLO threshold has a hysteresis of 470 mV.