Blue chip companies are incredibly important to any long-term portfolio and can even provide an invaluable source of income. I always hold multiple FTSE 100 dividend stocks that provide fantastic income to my portfolio. The three stocks below are trading at attractive levels so is it time to buy?

Asian heavyweight

Standard Chartered  (LSE: STAN) could become one of the best turnaround stories this year. The share price has fallen just under 50% in the last year but in the last three months the stock is up over 30%. The company had a terrible 2015 and loan impairments for the year came in at around the $4bn mark, which was up 87% from the previous year. This bad loan book along with continued worries about a Chinese hard landing led to furious selling of Standard Chartered shares in the second half of 2015. In response to the problems, the CEO announced a dividend cut, rights issue and the loss of 15,000 jobs. This has turned out to be a good decision and the company released solid Q1 2016 results at the end of April. The turnaround plan looks good here and I think shares will continue to creep higher. 

Telecommunications star

Talktalk Telecom Group  (LSE: TALK) has also had a difficult year and shares are down 40% since June 2015. The company has suffered multiple cyber attacks, which cost the group £42m and contributed to the £18m fall in full-year profits. The shares are currently trading on a forward price-to-earnings ratio (P/E) of 17 times and the company has a chunky dividend yield of 6%. Analysts expect it to grow well this year and to see increased profits and revenues. I think the company offers a compelling investment case of good growth prospects at a very reasonable price. Shares could easily trade above 300p in the near term and head back to previous highs. 

Chinese focus

Banking giant HSBC  (LSE: HSBA) has also been struggling due to the slowdown in Asia and deteriorating market sentiment towards the region. Shares are currently close to all-time lows but it could be a good time to take a contrarian view on the company. The shares trade on a P/E of only 10 and the company pays a whopping 7.6% dividend. City analysts seem to think HSBC is undervalued and many brokers have price targets of over 600p for the stock. If the company continues to perform then I see no reason why the shares can’t pass 600p and move even higher. The EU referendum is obviously a huge event for HSBC due to its London headquarters and UK operations. However, Asia accounted for 84% of profits last year so Asia is still much more important for the business. 

These three companies have all had problems to overcome in the last year but shares look attractive at current levels. HSBC and Standard Chartered are both heavily linked to the Asian economy, which seems to be stabilising. Talktalk should get back on track with good profit and revenue growth this year after being stung by one-off charges in 2015. 

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Jack Dingwall has no position in any shares mentioned. The Motley Fool UK has recommended HSBC Holdings. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.